Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Tue Apr 9 2024

.SYNOPSIS...Lingering moisture from a cold front will promote
showery weather conditions today. A slight improvement in weather
conditions is likely by midweek as drier-than-normal air moves in.
However, the remnants of the cold front will return by the end of
the workweek, increasing the chances for rainfall activity again.
Starting tonight, moderate to locally strong winds and a dominant
long-period northerly swell will deteriorate marine and beach
conditions. High surf conditions are possible on Wednesday.


&&

.SHORT TERM...Today through Thursday...

At surface level, a low pressure system over the northeastern
Atlantic has a cold front extending through the Atlantic, with its
remnants and related moisture affecting the islands and moving
southwards of the region, and a weak surface trough is near the
area. Over the western Atlantic, a surface high pressure system
continues to build, this system will spread eastward towards the
central Atlantic through the period. As an upper trough moves away
from the region, the mid to upper levels remain relatively stable
and available moisture extends to around 600 mb. Satellite
derived precipitable water (PWAT) show above normal values across
the islands and local waters. Normal to above normal PWAT values
will continue during the period, as moisture remnants from this
frontal boundary and prefrontal trough continue to be steered by
moderate to fresh northeasterly winds. This moisture will continue
moving southwards, but maintain above normal moisture over the
islands today, promoting variable to showery weather across most
of the region.

Like during the overnight hours, cloudiness and shower activity will
continue to be steered into windward sectors of the island from the
Atlantic Waters, promoting variable to showery weather. Afternoon
convection is still forecast, particularly across the interior to
southwestern Atlantic, although continued cloudiness during the
morning hours can serve to limit it. This activity however, can
still result in ponding of water on roads and poorly drained areas,
as well as urban and small stream flooding, especially with the
heaviest activity. On the bright side, heat risk no longer poses a
hazard. Temperatures are forecast to be cooler under these up to
breezy NE winds with 925 mb temperatures at below normal to normal
values for this time of the year due to the colder air mass behind
the front sinking southwards.

More normal PWAT values are forecast for Wednesday and then a drying
pattern is forecast on Thursday with PWAT values and overall
moisture decreasing. By Thursday night and into the long term
period, however, another patch of moisture, remnants of the past
frontal boundary, will filter into the region. Thursday will be the
driest day in the period (and the week). Wednesday and Thursday,
shower activity will affect windward sectors with more limited
convective activity over interior to SW PR, this activity will be
even more limited on Thursday.

.LONG TERM...Friday through Tuesday...

Model guidance suggests precipitable water values at or above
normal levels, except between Saturday evening and Monday morning.
This wet pattern results from distancing the mid-level ridge early
in the period, followed by the proximity of an upper-level trough
and associated jet early next week. The general steering flow at
lower levels should remain from the east throughout the period,
generated by a broad surface high pressure spreading across the
North Atlantic. However, as this feature weakens, wind speeds are
projected to weaken from 15-25 mph to 5-15 mph early next week.

In the expected scenario, heightened passing shower activity is
likely on Friday and from Monday onwards, affecting northern and
eastern sections of the local islands, with less frequent to
limited passing shower activity during the weekend. Afternoon
convective development is likely each, even during the driest
periods, with the highest impact across the western interior to
western Puerto Rico. Given the uncertainty in the forecast
associated with the timing of the wettest periods and the effects
of the upper-level trough, the excessive rainfall risk was kept at
low levels. However, the risk could elevate with a more direct
influence, and flooding impacts could start as early as Tuesday.
Breezy conditions will prevail through the weekend, leading to
limited wind impacts, mainly across coastal areas. Temperature
variations, in turn, should remain within seasonal levels
throughout the period.


&&

.AVIATION...
(06Z TAFS)

VFR conditions across the terminals, with possible MVFR conditions
from shower activity/low clouds. As SHRA from the Atlantic continue
to reach the islands, expect this activity affecting
TJSJ/TJBQ/TIST/TISX during the morning to afternoon hours. Afternoon
convective SHRA possible across the interior to SW PR, affecting
TJPS. Surface winds from the NE at 15-20 kts with higher gusts,
especially near stronger shower activity, and sea breeze variations.


&&

.MARINE...

An upper-level trough crossing the region along with a weak surface
trough approaching the area, will maintain the chance for showers
with isolated thunderstorm development today. Moderate to fresh
north to northeast winds will promote choppy seas today. Starting
this evening and continuing throughout the workweek, fresh to
locally strong winds and another dominant long-period northerly
swell will promote hazardous seas for small craft. For details,
refer to the Marine Weather Statement (MWWSJU).

&&

.BEACH FORECAST...

The rip current hazard risk will remain low to moderate today.
However, increasing winds and the arrival of a dominant long-
period northerly swell will deteriorate beach conditions starting
this evening, mainly across the north-facing beaches of Puerto
Rico. On Wednesday, these conditions will extend to the beaches of
Rincon and Aguada in western Puerto Rico, Culebra, and the
northern U.S. Virgin Islands. Large breaking waves exceeding 10
feet, possibly generating high surf and hazardous swimming
conditions, as well as localized coastal flooding and beach/dune erosion,
are possible on Wednesday. For details, refer to the Coastal
Hazard Message (CFWSJU) and Surf Zone Forecast (SRFSJU).

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Wed Apr 10 2024

.SYNOPSIS...Although there is still some moisture lingering
across the region, expect improved weather conditions today as
drier-than-normal air begins to move in. However, towards the end
of the workweek, projections suggest the return of the remnants of
the cold front, which will likely elevate the chances of showers
once again. The presence of an upper-level trough and increased
moisture levels may lead to an increased floosing early next week.
Additionally, moderate to locally strong winds, coupled with
pulses from a dominant long-period northerly swell, will persist,
maintaining hazardous marine conditions. Consequently, dangerous
swimming and life-threatening beach conditions are anticipated
during the next few days.


&&

.SHORT TERM...Today through Friday...

Current satellite derived precipitable water (PWAT) indicates most
of the above normal moisture, related to a frontal boundary south of
the region that affected the islands during the couple of few days,
in the southern half of the region, with values up to 1.75 in.
Across the islands, PWAT ranges from 1.34 to 1.55 in. As drier air
filters in, PWAT values today should remain at normal values for
this time of the year. At surface level, a surface high continues to
build, spreading from the western Atlantic to the central Atlantic
throughout the period. This system will promote breezy to windy
northeast winds through the period, with higher gusts and sea breeze
variations. These winds will steer even drier air into the region
tomorrow, Thursday, with PWAT values and overall moisture
decreasing. By Thursday night and into Friday, however, another
patch of moisture, remnants of the past frontal boundary, will
filter into the region promoting normal to above normal PWAT values.
Thursday will be the driest day in the period (and the week). The
mid to upper levels remain relatively stable, with only a possible
upper trough developing well east of the region. Available moisture
will extend to around 700 mb for most of the period.

925 mb temperatures at below normal to normal values for this time
of the year. Patchy fog is likely across areas of the interior
during the early morning hours. Periods of passing showers steered
by NE winds and afternoon showers cannot be ruled out during the
day, mainly across the interior to southwest Puerto Rico, as well as
on the west end and downwind of the USVI. This activity however, can
still result in ponding of water on roads and poorly drained areas.
Rain chances decrease tomorrow, with only less frequent shower
activity will affecting windward sectors with more limited
convective activity over interior to SW PR. Rain chances increase
Thursday night through, as the frontal remnants reach the islands.
Breezy to windy conditions will prevail, mainly across coastal areas.

.LONG TERM...Saturday through Wednesday...

TRrecent model guidance continues to suggest a significant shift
in weather patterns during the long-term forecast period,
transitioning from dry and stable conditions to a wetter and
unstable setup. Precipitable water values are expected to
fluctuate, starting from below-normal thresholds below 1.3 inches
on Sunday and Monday, then rising to above-normal thresholds
exceeding 1.7 inches on Tuesday and Wednesday. This transition is
attributed to the retreat of the mid-level ridge and presence of a
drier-than-normal air mass during the weekend, followed by an
influx of tropical moisture and the proximity of an upper-level
trough early next week. The prevailing steering flow should remain
easterly, driven by a broad surface high pressure spreading across
the North Atlantic. However, as this feature weakens, wind speeds
are forecast to diminish from approximately 15-25 mph to 5-15 mph
early next week.

While fair weather conditions are expected until early Monday, the
possibility of passing showers overnight and limited afternoon
convective activity exists each day. Conversely, an increase in
shower activity with potential isolated thunderstorm development
is expected from Monday night onward as conditions become
increasingly favorable for deep convective development, with 500
mbar temperatures dropping as low as -9 degrees on Wednesday. The
anticipated rains may lead to flooding impacts, although the
excessive rainall risk level remains uncertain at this time.
However, if the trough's influence becomes more direct, an
elevated flooding risk is likely and flooding impacts could occur
as early as Tuesday morning. Breezy conditions are anticipated
through the weekend, primarily affecting coastal areas, with limited
wind impacts expected. Temperature fluctuations should remain
within seasonal thresholds throughout the forecast period.


&&

.AVIATION...
(06Z TAFS)

Mostly VFR conditions expected across the terminals. Passing SHRA or
VCSH can affect TJSJ/TJBQ/TIST/TISX. SHRA developing during the
afternoon, spreading to S/SW PR, may cause MVFR at TJPS.
Surface winds from the NE at 15-20 kts with higher gusts, especially
near stronger shower activity, and sea breeze variations.


&&

.MARINE...

A surface ridge building across the western Atlantic will generate
fresh to locally strong northeast winds throughout the workweek,
causing an increase of passing showers and brief gusty winds. Pulses
of a dominant long-period northerly swell will continue to spread
across the Atlantic waters and local passages through Thursday.
The wind and swell interaction will maintain hazardous seas for
small craft for the rest of the week. For details, refer to the
Marine Weather Statement (MWWSJU).

&&

.BEACH FORECAST...

Increasing winds and a dominant long-period northerly swell will
likely generate dangerous swimming and life-threatening rip
current condition, due to large breaking waves of up to 12 feet.
Given these conditions, a High Surf Advisor and High Rip Current
Risk are in effect for the north-facing beaches of Puerto Rico,
Culebra, and the northern US Virgin Islands, where localized
coastal flooding and beach/dune erosion is possible. Between
tonight and thursday, life-threatening rip current conditions
will spread to the beaches of Vieques and St Croix. For details,
refer to the Coastal Hazard Message (CFWSJU) and Surf Zone
Forecast (SRFSJU).

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
523 AM AST Thu Apr 11 2024

.SYNOPSIS...Breezy conditions expected through Saturday. The
remnants of an old front will move across the region from later
today through early Saturday. A drier air mass should prevail
through Monday morning. An upper-level trough and higher moisture
content is expected to increase shower and thunderstorm activity
across the islands during by midweek next week. Hazardous seas and
life threatening rip currents will continue for the next few
days.


&&

.SHORT TERM...Today through Saturday...

An overnight radar and satellite imagery analysis indicated
persistent passing shower activity affecting northern and eastern
Puerto Rico, with less frequent showers across Vieques, Culebra, and
the US Virgin Islands. In the last 6 hours, surface observing
stations have reported up to a quarter of an inch in isolated areas.
Clear to partly cloudy skies prevailed elsewhere, particularly over
southwestern Puerto Rico. As reported by official sites, overnight
minimum temperatures ranged from 62 degrees in higher elevations to
78 degrees across lower elevations. Winds were generally from the
east to east-northeast at 10-15 mph with gusts up to 20-25 mph
across windward areas, but light to calm and variable elsewhere.

A strengthening high-pressure system over the western-central
Atlantic will maintain breezy east-to-east-northeast trade winds
during the forecast period. These conditions will be most noticeable
in windward areas, where daytime wind speeds are expected to peak at
15 to 20 mph, diminishing to 10-15 mph at nighttime. The sea breeze
may cause slightly higher speeds and gusts throughout the day. The
prevailing wind flow will maintain an influx of moisture from the
remnants of an old frontal boundary, maintaining moisture levels
within seasonal levels, with precipitable water values fluctuating
between 1.3 and 1.7 inches through Saturday afternoon. By Saturday
night, a drier-than-normal airmass will cause precipitable water to
fall below seasonal thresholds. Meanwhile, a persistent mid-level
ridge and associated trade wind inversion, centered across the
Greater Antilles and west of the forecast area, will prevent
significant convective development. The gradual weakening of the
trade wind inversion is likely from Friday onward as the ridge
shifts further westward.

Passing showers, driven by the prevailing flow, will continue to
affect northern and eastern Puerto Rico, Vieques, Culebra, and the
US Virgin Islands this morning. As the day progresses, the focus of
the showers will shift further inland, driven by sea breeze
convergence, clustering over central to western-southwestern Puerto
Rico. Despite hostile conditions, shallow afternoon convection, like
the morning activity, is likely to occur, producing rainfall totals
of as much as half an inch. Minor flooding on roads and poorly
drained areas is possible. By tonight, the showers' focus will shift
to the local waters into windward areas, producing similar rainfall
amounts. Temperatures should range from the mid 80s at daytime to
around 60 degrees at nighttime. Breezy conditions, as previously
stated, will persist, with a limited to elevated wind hazard risk
across coastal areas and the local islands, where unsecured or
outdoor items could blow around or be damaged.

Friday is expected to follow a similar weather pattern, with
potentially higher rainfall totals and a broader area under a
limited flooding risk as conditions become more conducive to deep
convective activity. However, as moisture levels decrease on
Saturday, fair weather conditions are likely, with fewer and less
frequent showers. Nonetheless, breezy conditions will persist,
posing a limited wind hazard risk.

.LONG TERM...Sunday through Thursday...

Fair weather conditions are expected to prevail on Sunday as a drier
air mass moves briefly over the region. However, diurnally induced
afternoon showers are expected to develop over portions of the
southwestern quadrant of Puerto Rico. Seasonable temperatures are
expected to prevail through early next week. Weakening of the
surface ridge is expected by Monday, and winds speeds will
decrease in general as a front approaches from the northwest, but
remains well north of the region. At the same time and through
midweek, a strong upper level trough is expected to linger over
the region. In response, an induced surface trough is expected to
develop over the eastern Caribbean and promote moisture pooling
over the islands. Therefore, the potential for thunderstorm
activity will increase, as well as for flooding rains as a wetter
and unstable pattern evolves through at least Wednesday night.
Model guidance suggest a quick drying trend from Thursday onwards.


&&

.AVIATION...

(06Z TAFS)

Mainly VFR conditions are expected across all terminals,
with prevailing E-NE winds at 10-15 knots increasing to 15-20 knots
between 11/13-23Z, accompanied by higher gusts and sea breeze
variations. SCT-SHRA may cause VCSH to SHRA and, thus, brief MVFR
conditions across TJSJ through most of the forecast period, USVI
terminals through 11/13Z, and between 11/16-22Z across TJBQ.


&&

.MARINE...

A surface ridge now extending eastward into the central Atlantic
will continue to generate fresh to locally strong east-northeasterly
winds through the rest of the week. This will aid in bringing
periods of passing showers and brief gusty winds to the regional
waters. Northerly swells will continue to spread across the
Atlantic waters and passages through tonight. The wind and swell
interaction will maintain confused, hazardous seas for small craft
over the next few days. For detailed information, please refer to
the Marine Weather Statement (MWWSJU). Seas are forecast to
improve briefly late in the weekend into early next week, and
mainly across the southern and western waters of the islands.


&&

.BEACH FORECAST...

Increasing winds and a long-period northerly swell will generate
dangerous swimming and life-threatening rip current condition,
due to large breaking waves of up to 12 feet and higher at times.
Given these conditions, a High Surf Advisory and High Rip Current
Risk are in effect for the northwest to northeast beaches of
Puerto Rico, Culebra, and the northern US Virgin Islands, where
localized minor beach erosion is possible. Across Vieques and St.
Croix, there is a High Rip Current Risk in effect. For detailed
information, please refer to the Coastal Hazard Message (CFWSJU)
and Surf Zone Forecast (SRFSJU). The high risk of rip currents
will continue through the weekend across the north-facing beaches
of the islands.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
441 AM AST Fri Apr 12 2024

.SYNOPSIS...

Breezy conditions and passing showers will continue through
Saturday as the remnants of a front continues to cross the region.
Locally induced afternoon showers are expected during the weekend
over western PR, and from streamers developing off the
USVI/Eastern PR. A mid- to-upper-level trough and higher moisture
content are expected to increase shower and thunderstorm activity
across the islands from Monday through Wednesday. Hazardous seas
and life-threatening rip currents will continue for the next few
days.


&&

.SHORT TERM...Today through Sunday...

An overnight radar and satellite imagery analysis indicated
persistent shower activity affecting the area, with less frequent to
no showers across southwestern Puerto Rico. In the last 6 hours,
radar estimates indicated the highest rainfall totals, ranging
between 0.5 and 1.5 inches along an area stretching from central Toa
Baja westward to northern Barceloneta and around El Yunque National
Forest. As reported by official sites, overnight minimum
temperatures ranged from 65 degrees in higher elevations to 78
degrees across lower elevations. Winds were generally from the east
to east-northeast at 10-20 mph with gusts up to 25-30 mph across
windward areas, but light to calm and variable elsewhere.

The forecast for the short-term forecast period remains unchanged.
Breezy to windy east-to-east-northeast trade winds, driven by a
strengthening high-pressure system over the western-central
Atlantic, will continue to affect the area throughout the forecast
period, with wind speeds ranging from 15 to 25 mph at daytime,
diminishing to 10-20 mph at nighttime. Although a slight weakening
of this flow is likely during the weekend, breezy conditions will
persist. The prevailing wind flow will maintain an inflow of
moisture today, bringing precipitable water to above-seasonal levels
to approximately 1.8 inches this afternoon. A drier-than-normal
airmass will likely bring precipitable water values below seasonal
thresholds of around 1.0-1.2 inches by Sunday morning. However, this
will be short-lived, and an even wetter airmass will cause a spike
in moisture levels starting Sunday evening, with precipitable values
exceeding well above seasonal levels. The leading mid-level ridge
will gradually shift west-southwestward and away from the local
islands, steered by a mid-to-upper level trough sinking southward
across the western Atlantic. This transition should weaken the trade
wind inversion and allow moisture to ascend beyond the 700 mbar
layer. However, another ridge is forecast to cross the local islands
on Saturday, briefly supporting the reinstatement of the trade wind
cap.

Passing shower activity, driven by the prevailing flow, will
continue to affect most of the forecast area today. As the day
progresses, the focus of the showers will shift to central to
western Puerto Rico, as well as regions downwind from isolated
mountainous areas and the local islands. With conditions becoming
more favorable for deep convective development, afternoon showers
will likely produce significant rainfall totals of as much as 1.0-
2.0 inches across western Puerto Rico, where urban and small stream
flooding is likely. By tonight, the showers' focus will shift again
to the local waters and windward areas, producing isolated rainfall
amounts of up to half an inch. Temperatures should range from around
85 degrees at daytime to around 65 degrees at nighttime. Breezy to
windy conditions, as previously stated, will persist, with a limited
to elevated wind hazard risk across coastal areas and the local
islands, where unsecured or outdoor items could blow around or be
damaged.

Saturday is expected to follow a less showery weather pattern as a
drier-than-normal airmass begins to invade the region, followed by
an even drier and more stable weather pattern on Sunday morning.
However, as moisture levels rise and conditions become more
conducive for deep convective development by Sunday afternoon,
expect an increase in shower activity and, thus, higher rainfall
totals that could heighten flooding risks. Breezy conditions will
persist, posing a limited wind hazard risk.


.LONG TERM...Monday through Friday...

On Monday, the surface ridge over the central Atlantic will
weaken, and wind speeds will decrease as a front approaches from
the northwest. However, it will remain well north of the region.
At the same time, a mid-to-upper-level trough will move from the
southwestern Atlantic into the northeastern Caribbean and linger
over the area through midweek, providing good divergence aloft and
favorable dynamics for thunderstorm development as the 500 mb
temperatures are forecast to drop to around minus 8 degrees
Celsius. Meanwhile, an induced surface trough will develop over
the eastern Caribbean, leading to moisture pooling over the
islands. As a result, there is potential for thunderstorm activity
and flooding rains as a wetter and unstable pattern evolves
through at least late Wednesday night. According to model
guidance, there will be a quick drying trend from Thursday onwards
as an upper-level ridge builds from the western Caribbean,
promoting drier air intrusion and warming of the 500 mb
temperatures.


&&

.AVIATION...

(06Z TAFS) VFR conditions are likely across all terminals as trade
wind and afternoon SHRA affect the area. Expect these conditions
across TJSJ and USVI terminals throughout the period, after 12/16Z
at TJBQ, and after 12/23Z at TJPS. Prevailing E-NE winds at 10-20
knots increasing to 15-25 knots between 12/13-23Z, accompanied by
higher gusts and sea breeze variations. Higher winds and gusts are
likely near SHRA.


&&

.MARINE...

Fresh to locally strong east-northeasterly winds will continue
through early Saturday morning. Embedded in this wind flow, the
remnants of a front will bringing periods of passing showers and
brief gusty winds across the local waters. A fading northerly
swell and choppy wind-driven seas will continue to promote
hazardous conditions to small craft. Please refer to the latest Marine
Weather Message (MWWSJU) for detailed information. Seas are
forecast to improve briefly late in the weekend into early next
week.


&&

.BEACH FORECAST...

Dangerous swimming and life-threatening rip currents will continue
through at least Saturday across the east and north-facing
beaches of PR and the USVI, due to rough surf conditions with
breaking waves around 6 feet and higher at times. Given these
conditions, a High Rip Current Risk remains in effect for the
northwest to northeast beaches of the islands. Please refer to the
latest Coastal Hazard Message (CFWSJU) and Surf Zone Forecast
(SRFSJU) for detailed information. Beach goers should remain alert
as a moderate risk of rip currents will continue on Sunday across
across most east and northern beaches of the islands.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
458 AM AST Sat Apr 13 2024

.SYNOPSIS...
A strong surface ridge over the north-central Atlantic and a weak
surface trough associated with the remnants of a frontal boundary
across the Caribbean waters, will promote moderate to locally strong
east- northeasterly winds and passing showers across the region during
the rest of the early morning hours. A gradual break in cloud cover
and a decrease in the frequency of the passing showers is forecast later
this morning and during the rest of the day. Drier air filtering in
from the north and building high pressure ridge aloft will reduce the
frequency of the passing showers during the rest of the weekend. Breezy
conditions and occasional passing showers will however continue through
the weekend, with afternoon showers expected to develop over parts of
the central interior and west to southwest sections of Puerto Rico
and mainly on the west-end and downwind of the U.S. Virgin Islands.

&&

.SHORT TERM...Today through Monday...

Cloudy skies prevailed through the overnight hours across the
islands as the remnants of an old front crossed the region. The
Doppler radar noted persistent light to moderate showers with this
moisture band across Puerto Rico through the early morning hours.
The radar estimated between 1-2 inches of rain across eastern Puerto
Rico, and from a few hundredths to half an inch elsewhere across the
island. Across the USVI, rainfall totals were less than a tenth of
an inch. Minimum temperatures were from the mid-60s across the
higher elevations to the mid-70s across the lower elevations. Wind
gusts were between 16 and 22 mph across coastal areas.

For the rest of the weekend, the area will remain under the
influence of a mid-level ridge extending from the west. Although
drier air will gradually filter later today and through early
Sunday, patches of low-level moisture will move at times from the
Atlantic waters as east-to-northeast steering winds prevail through
the short-term period. Breezy conditions should continue today
across the region and return briefly by Monday morning across the
Caribbean waters and the USVI. The precipitable water content is
forecast to drop between 1.25 and 1.50 inches through Sunday
afternoon. Therefore, shower activity should develop mainly due to
diurnal and local effects and mainly across portions of
west/southwest PR each afternoon.

A more unstable and wetter pattern is expected to evolve on Monday
as a mid-to-upper-level trough moves from the northwest and a low-
level trough develops over the eastern Caribbean. These features
will cause the precipitable water content to increase again between
1.75-2.00 inches, promoting colder 500 mb temperatures of near -7
degrees Celsius. Therefore, shower and thunderstorm activity is
expected to increase across the local area. The threat for urban and
small stream flooding will remain elevated during the first part of
the workweek.

.LONG TERM...Tuesday through Saturday...
Tuesday through at least Wednesday a very moist and unstable
environment will persist due to the presence of the mid to upper
trough crossing into the northeastern Caribbean then lingering over
the area through midweek. This will provide good ventilation and
divergence aloft along with strong dynamics for thunderstorm development,
as the 500 mb advective temperatures are forecast to range between
minus 7 to minus 9 degrees Celsius. Meanwhile, increasing moisture
convergence and pooling is forecast due to an induced surface trough
and the dominant east southeast winds. As a result, the potential
for thunderstorm development and flooding rains will be high as this
wetter and unstable pattern will evolve and continue through at least
Wednesday. Based on most recent GFS model guidance which has been
initializing fairly well, there will be a gradual drying trend from
Thursday onwards as a mid to upper- level ridge builds from the
western Caribbean, and a surface high pressure ridge builds across
the west Atlantic. This will promote east to northeast winds once
again, with winds becoming more easterly by the following weekend.
This expected pattern will also lead to an overall drier airmass
across the region at least Thursday through Friday, followed by
the return of occasional passing trade wind showers and more
isolated to scatters afternoon showers in and around the islands
over the weekend.

&&

.AVIATION...

(06Z TAFS)

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hours. However, brief MVFR areas should end around
13/10z at TJPS/TJBQ as the remnants of an old frontal boundary moves
westward across the Mona Passage. Winds will continue from the ENE
btw 12-18 kts with gusts at 20-30 kts. Sea breeze variations expected
aft 13/13z at TIST/TISX/TJPS.

&&

.MARINE...
A strong surface ridge over the north-central Atlantic and a weak
surface trough associated with the remnants of a frontal boundary
across the Caribbean waters will continue to generate fresh to
locally strong east- northeasterly winds and passing showers
across the regional waters. The arrival of drier air filtering in
from the north later today will reduce the frequency of the passing
showers during the rest of the weekend. However the breezy conditions
and occasional passing showers will continue. A fading northerly swell
today and choppy wind- driven seas will maintain hazardous conditions
to small craft. Therefore small craft advisories and precautionary
statement will continue for portions of the regional waters through
the weekend. Please refer to the latest Marine Weather Message (MWWSJU)
for detailed information. Seas are forecast to slightly improve late
Sunday into early next week.

&&

.BEACH FORECAST...
Dangerous swimming and life-threatening rip currents will continue
through at least later this afternoon across the east and north-
facing beaches of PR and the USVI, due to wind driven seas, rough
surf conditions with breaking waves around 6 feet and higher at
times. Given these conditions, a High Rip Current Risk remains in
effect for the northwest to northeast beaches of the islands.
Please refer to the latest Coastal Hazard Message (CFWSJU) and
Surf Zone Forecast (SRFSJU) for detailed information. Beach goers
should remain alert as a moderate risk of rip currents will
continue through the rest of the weekend across most east and
northern beaches of the islands.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
505 AM AST Sun Apr 14 2024

.SYNOPSIS...
A surface ridge over the north-central Atlantic and a broad induced
trough extending northwards from across the eastern Caribbean, will
promote moderate east- northeasterly winds during the rest of the
morning, then become more easterly in the afternoon and on Monday,
as the surface trough spreads farther westwards into the east central
Caribbean. A slot of drier air crossed the region overnight with only
a few passing showers noted across the local waters and brushing the
coastal areas of islands from time to time. A wetter weather pattern
is expected by late afternoon and into the early part of the upcoming
week due to the interaction of an amplifying upper- level trough and
increasing tropical moisture associated with the broad surface trough
across eastern Caribbean. This will support increasingly moist and
unstable conditions across the region, with high potential for
shower and thunderstorm development and the chance for heavy
rainfall across the region. Consequently there will be a heighten
risk of flooding and possible landslides across the forecast area.

&&

.SHORT TERM...Today through Tuesday...

Clear to partly cloudy skies were observed throughout the overnight
hours. An area of low to mid-level moisture reached the eastern
Caribbean, and passing showers were noted across the Anegada Passage.
Light showers were noted over land areas at times. Minimum temperatures
ranged from the low and mid-60s at higher elevations to the mid and
upper 70s at coastal areas. Wind gusts were around 20 mph in coastal
regions.

A more unstable and wet weather pattern will evolve earlier than anticipated
during the short-term period. A surge in moisture from the Leeward Islands
will reach the local area throughout the day today. This will increase
the frequency of passing showers across portions of the USVI and eastern
PR, followed by diurnally induced afternoon showers over the interior
and western sections of PR. Be prepared for ponding of water on roads
and low-lying areas, with increasing chances for minor flooding by
tonight across the eastern half of the CWA.

On Monday and Tuesday, a further increase in showers and thunderstorm
development is expected across the islands as a mid-to- upper-level
trough moves from the northwest and a low-level trough develops over
the eastern Caribbean. These features will promote colder 500 mb
temperatures of -7 to -8 degrees Celsius and cause the precipitable
water content to remain above normal levels (around 2.00 inches) through
the first half of the workweek. The threat of urban and river flooding
will remain elevated during the first part of the workweek. There is
also a possibility of isolated flash flooding and landslides/rockfall
in steep terrain.

.LONG TERM....Wednesday through Sunday...
Wednesday through at least early Thursday morning, inclement
weather and a moist and unstable environment will persist due to
the lingering mid to upper trough crossing into the northeastern
Caribbean. This will provide good ventilation aloft along with the
advective low level moisture pooling for a continued showery pattern
and isolated thunderstorm development. The low level moisture convergence
caused by the east southeast winds and local and diurnal effects will
favor good potential for thunderstorm development and flooding rains
at least until late Wednesday or early Thursday. Thereafter, recent
model guidance continued to initialize well and still suggest moisture
erosion with increasing stable conditions aloft by Thursday afternoon.
A gradual drying trend is expected from then onwards, as a mid to upper-
level ridge will build northwards from the western Caribbean, and a
surface high pressure ridge builds across the west Atlantic. This in
will bring a return of east-northeast winds once again through Friday,
followed by winds becoming more easterly and increasing over the
following weekend. This expected pattern will also lead to an overall
drier airmass at least Thursday through Friday, followed by the return
of occasional passing trade wind showers and more typical isolated
to scattered afternoon showers in and around the islands over the
weekend.

&&

.AVIATION...
(06z)

Mainly VFR conditions expected early in the cycle. SCT/BKN cigs at
FL030-FL060 and periods of SHRA could increase around 14/14z across
the USVI terminals, and after 14/18z across the PR terminals. Winds
will continue from the ENE at 13-17kts, with higher gusts and sea
breeze variations aft 14/13z. MVFR to brief IFR conditions are
possible aft 15/00z and through Monday morning, mainly at
TIST/TISX/TJSJ.

&&

.MARINE...
A surface ridge over the north-central Atlantic and broad trough
over the eastern Caribbean will generate moderate to locally fresh
east- northeasterly winds. A fading northerly swell and choppy wind-
driven seas will continue to promote confused seas. The interaction
of an approaching upper level trough and a broad induced surface trough
spread across the eastern Caribbean will promote increasing
shower and thunderstorm activity across the local waters beginning
by later this evening and into early next week.

&&

.BEACH FORECAST...
Pulses of a weak north-northeasterly swell will continue across
the northern regional waters the rest of today. Additionally wind-
driven seas will contribute to hazardous breaking waves to around
6 feet. As a result, the Rip Current Statement was extended through
at least until Monday afternoon for all beaches across the northern
coastline of Puerto Rico and Culebra. For more information and details
please refer to the latest Surf Zone Forecast (SRFSJU), and the Coastal
Hazard Message product (CFWSJU).

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
441 AM AST Wed Apr 17 2024

.SYNOPSIS...

Unstable weather conditions are expected to prevail across the
local area through at least today. Showers and isolated
thunderstorms are also expected during the overnight hours.
Therefore, there is the potential for minor flooding, river rises
and mudslides due to soil saturation. Conditions should improve
tomorrow into the weekend, however wet conditions are expected
next week. Marine conditions will slowly improving across the
local waters, however, a northeasterly swell is forecast to
arrive Thursday.

&&

.SHORT TERM...Today through Friday...

A broad surface trough extending across the northeast Caribbean and
surface high pressure over the southwest Atlantic will maintain
light east northeast winds across the area today into Thursday, then
forecast to become more easterly by Friday. A mid to upper level
trough will continue to slowly shift eastward across the region
through Thursday, then linger across the northern Leeward Islands by
Friday with another short wave trough forecast to cross the west
Atlantic and just north of the region by then. The proximity of the
upper trough along with the surface trough and a weak area of low
pressure now forecast to develop northeast of the region over the
next few days will support a fairly moist and unstable environment
through the period.

Recent satellite imagery and doppler weather radar showed mid to
high level cloudiness and light to moderate showers accompanying the
upper trough just west and north of the region, while fewer showers
were noted over the islands and coastal waters steered by the east
northeast winds. Shower activity continued to wane over land areas
overnight, while rivers and streams slowly subsided. However another
round of developing showers is expected to affect the islands later
this morning and during the afternoon aided by local and diurnal
effects. Early morning low temperatures remained in the mid to upper
70s along the coastal areas and in the upper 60s to low 70s in
higher elevations. Winds were calm to light and variable.

Through the rest of the period, unstable weather conditions are
forecast to continue, due to the meandering upper trough and good
low level moisture convergence. Present model guidance as well as
recent satellite derived precipitable water products and analyses
all suggest precipitable water values ranging between 1.70-1.85
across the region today. However this is forecast to gradually
diminish to between 1.65-1.70 inches by Friday favoring less
widespread shower activity and deep convection. The overall scenario
still suggests sufficient instability aloft and plenty of moisture
available for enhanced of overnight showers and isolated
thunderstorms across portions of the islands and local waters during
most of the period. Developing showers with periods of locally heavy
rains will be possible each day and any additional rains may lead to
ponding of water and flooding in flood prone areas as well as
quickly reacting rivers and streams along with water surges with
flash flooding, and landslides.

&&

.LONG TERM...Saturday through Wednesday...

Areas of low pressure spread across the central Atlantic basin and
developing surface high in the western Atlantic will maintain
moderate NE winds through the weekend along with enough water
content in a lingering airmass to allow passing showers and
afternoon convection to fire up due to diurnal heating and local
effects. By Sunday, an area of lower pressure near Florida will
assist the lifting of a moist airmass from the eastern Caribbean,
raising precipitable water values well above average values. This
in combination with a mid to upper-level trough, with the jet max
over the region through late Sunday, will allow an increase of
passing showers and afternoon convection mainly across western
Puerto Rico.

Winds begin to strengthen and veer, becoming more easterly to
southeasterly Monday to Tuesday, respectively, as the aforementioned
surface high moves into the central Atlantic. Due to all of this a
wet pattern is expected from Sunday onward with Wednesday containing
a best chance for widespread rainfall.


&&

.AVIATION...
(06z)

Wdly SCT SHRA/Isold TSRA psbl across the local flying area due to
proximity of a surface trough an upper trough slowly crossing the
region from the northwest. SCT-BKN lyrs nr FL025...FL050...FL080.
Brief MVFR conds psbl due to SHRA/LOW CIG nr SHRA en route to TJSJ
and USVI terminals during the early morning hours. Isold TSRA ovr
offshore Atl waters N of the islands. Brief MTN TOP OBSCR psbl ovr
Ern PR due to -RA/LOW cld lyrs til 17/14Z and over west and ctrl
interior of PR fm 17/16z-23Z. VCSH psbl at TJBQ/TJSJ and USVI
terminals durg prd. SFC Winds lgt/vrb bcmg fm E-NE 10-15 kts and
ocnly hir gusts aft 17/14Z.


&&

.MARINE...
A surface ridge over the north-central Atlantic and broad surface
trough across the eastern Caribbean will generate moderate to locally
fresh east to northeasterly winds through tonight. An upper level
trough and induced surface trough will continue to promote inclement
weather across the local waters over the next few days, with squally
weather and thunderstorms possible at times. A northeasterly swell
is forecast to arrive by tomorrow.

[cycloneye]

AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
510 AM AST Thu Apr 18 2024

.SYNOPSIS...

Trofiness aloft will persist through next week; thus, afternoon
convection due to local effects may result in thunderstorms across
the interior and western sections. Any persistent moderate to
locally heavy rain over the already saturated soils may result in
river flooding or sudden mudslides along steep terrains this
afternoon. A surface high-pressure migrating from the western
Atlantic to the Central Atlantic from this weekend into next will
promote an advective pattern from Sunday onward.

&&

.SHORT TERM...Today through Saturday...

Showers developed over Puerto Rico and the USVI throughout the early
morning hours, with up to half an inch near Trujillo Alto and less
elsewhere. Winds lightened and became variable with speeds around 3
mph at 4am this morning. Heavy rainfall yesterday caused Rio Grande
de Manati and Rio Cibuco at Vega Baja to overflow their banks,
causing flooding on the roads they intersect. Due to this Flood
Warnings were issued until the morning.

As the mid to upper-level and associated surface trough continue to
pass through region unstable conditions will persist. By this
morning, the surface trough has already moved past the USVI and due
to it's positioning the surface winds will prevail from the NE today
with light to moderate speeds, with stronger gust during the
afternoon. By this afternoon the area will be under the stable side
of the upper-level trough, however diurnal heating, local effects
and lingering moist air will allow convection to bring heavy
rainfall mainly across the interior to western sections of Puerto
Rico. Due to previous days of heavy rainfall soils are already
saturated which will increase the chance of runoff resulting in
flash flooding and possible mudslides across areas with steep
elevation.

By tonight, conditions will begin to improve overall with the
exiting of the upper-level trough and the mixing of drier air into
the region as northerly winds prevail. A surface high begins to
build in the western Atlantic, causing wind speeds to increase from
the NE to N. Besides ongoing passing showers throughout the morning
for northern and eastern PR and the USVI, Friday afternoon still
holds a good chance to bring noticeable rainfall for southwestern
to interior sections of Puerto Rico. A similar pattern will
prevail on Saturday with southwestern Puerto Rico having the best
chance of heavier rain. Temperatures are expected to be slightly
cooler for northern coastal areas these days due to northerly
wind. Again, for these days, flooding of small streams and urban
areas remains totally possible with the heaviest activity mainly
across the interior to western sections of PR during the afternoon
hours.


.LONG TERM...Sunday through Thursday...

A surface high-pressure building north of the islands, promoting
an advective pattern, will bring occasional moisture surges across
the USVI and PR from Sunday onward. The winds will persist mainly
from the east to east-northeast, which may result in the areas
affected by passing showers being the islands' north and east
windward sections, especially during the night and morning hours.
These showers will bring periods of moderate to locally heavy
rains at times. The afternoon convection will be driven mainly by
local effects, diurnal heating, and sea breeze variations across
the interior and western sections daily. Additionally, the latest
model guidance suggests maximum temperatures near the normal
climatological values during the long term.

Around mid-week, an upper-level trough will approach from the
west, increasing the local instability, which, combined with the
sea breeze, orographic effects and diurnal heating could result in
the typical strong afternoon convection of a wet April.

&&

.AVIATION...
(06z)

VCSH are expected to continue across the local area through at least
tonight. Periods of reduced VIS and low CIGs are possible during the
afternoon with thunderstorm development. Winds are light and
variable this morning and then will become NE at 10-15 kts aft
18/14z, with stronger gusts.

&&

.MARINE...
A set of surface troughs, one to the northwest and other to the
northeast of the islands will promote light to locally moderate
northeast winds today. A small northeasterly swell will move across
the Atlantic water from today onward. The surface trough northeast
of the region and a surface high pressure building across the western
Atlantic will promote moderate to locally fresh trades by the
weekend.

&&

.BEACH FORECAST...
A northeasterly swell, spreading across the local Atlantic, and
the locally wind-seas will result in a moderate risk of rip
currents along the north and east facing beaches in PR and the
USVI. The northeasterly swell will continue throughout the
weekend.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
406 AM AST Fri Apr 19 2024

.SYNOPSIS...
The risk of flooding will remain elevated today, especially for the
municipalities along the interior. Another active afternoon is
expected under a light wind flow. Soils are saturated and rivers are
running high, so even little precipitation may result in flooding
and mudslides. This afternoon activity will continue for the next
few days. Some Saharan dust could reach the islands early in the
next workweek, and temperatures are expected to warm up too.

&&

.SHORT TERM...Today through Sunday...

Showers lingered across the interior sections of Puerto Rico during
the evening hours however cleared before midnight when an increase
of passing showers over northern Puerto Rico and the USVI were seen.
Winds lightened and became variable with speeds around 3 mph this
morning. Heavy rainfall yesterday caused Rio Grande de Manati and
Rio La Plata to overflow their banks, causing flooding on the
roads they intersect. Due to this, flood warnings were issued
until the morning.

A light lower level steering flow is hinting at another afternoon
of active weather for the interior to southern sections of Puerto
Rico. Meanwhile, passing showers across windward sections will
continue. During the afternoon, convection will likely begin
across southwestern PR, then spreading eastward along the
Cordillera Central. Thunderstorms are possible and will be
capable of producing lightning and strong wind gusts. Heavy
rainfall is very likely with a few inches of accumulation possible
across sections that are already saturated due to previous days
of rainfall. Due to this, there is an elevated to significant
risk of flooding for the central interior sections of Puerto Rico
today. Take caution and watch for rapid river rising, mudslides,
and flooded streets.

Showers are expected to linger through the early evening hours.
However, the arrival of drier air will limit the amount of rain
seem through the night. Passing showers remain possible. As an
area of high pressure at the surface located in the western
Atlantic continues to build, light to moderate NE winds will
continue. This will concentrate Saturday's afternoon convection
across the southwestern sections of Puerto Rico. However, due to
the arrival of drier air, less rain is forecast compared to the
previous days. A similar pattern is expected on Sunday as the
aforementioned surface high moves north of the region causing
veering in the surface winds to an easterly direction, which will
bring the best chance of rain across the interior to western
sections of Puerto Rico.

.LONG TERM...Monday through Friday...

The next workweek will begin with a 60% chance of experiencing above
normal precipitation across the local islands. First of all, a high
pressure system northeast of the islands will maintain the winds
from the southeast at around 8 knots. A straight line of moisture
stretching from a low pressure system just east of the high pressure
will keep a dense Saharan-Air-Layer just south of the local islands
on Monday. However, small concentrations of these particulates could
reach the islands, so skies may look hazy at times. With moisture
lingering around, showers and isolated thunderstorms are anticipated
to develop along the Cordillera Central in the afternoon. The winds
from 850 to 700 mb are expected to be from the south, so this
convection will move northward, possible reaching portions of the
San Juan metro area.

Then, another low pressure system is expected to exit the eastern
coast of the United States, and the surface high will migrate
northward. The line of moisture will continue to meander around the
northeastern Caribbean, providing enough moisture to fuel afternoon
convection through Thursday. On Friday, additional induced patches
of moisture will be dragged across the region, but more breaks of
sunshine are expected.

Even with the afternoon rains, enough heating is expected late in the
morning, and with a southerly flow, temperatures will be on the hot
side, with highs reaching the upper 80s and low 90s, and heat
indices above the 100 degree mark.


&&

.AVIATION...
(06z) TAFS

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hours. However, tempo MVFR conds are possible at
TJPS thru 19/19z-22z due to vicinity TS. Low level winds will
continue from the north-northeast around 10 kt.

&&

.MARINE...
A set of surface troughs, one to the northwest and other to the
northeast of the islands will promote light to locally moderate
northeast winds today. A small northeasterly swell will move across
the Atlantic waters through the weekend. The surface trough
northeast of the region and a surface high pressure building across
the western Atlantic will promote moderate trades by the weekend.

&&

.BEACH FORECAST...
A small northeasterly swell will continue to move across the
local islands, maintaining the risk of rip currents moderate for
northern Puerto Rico, Culebra and eastern St. Croix.

&&

.HYDROLOGY...
Another round of strong showers and thunderstorms is expected for
today under a very light wind flow. Due to previous rainfalls,
soils are saturated and rivers are running high in the interior of
Puerto Rico. Therefore, the risk for flooding and mudslides will
be elevated again today. Additionally, it is likely that afternoon
activity will not only focus on the main island of Puerto Rico,
but Vieques, Culebra and the Virgin Islands could see convection
popping up as well.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
451 AM AST Sat Apr 20 2024

.SYNOPSIS...

Some improvement may be observed today. However, a wet and unstable
weather pattern is expected to return by the end of the weekend and
persist through the workweek.

&&

.SHORT TERM...Today through Monday...

Runoffs from previous rainfall caused Rio Grande de Manati in
Manati, and Rio de la Plata in Dorado to reach flood stage once
again. However, waters receded around 4 AM AST. Under a northeast
flow, showers moved across north-central Puerto Rico and over Saint
Croix, with rainfall accumulations up to 1 inch in Vega Baja. For
western Puerto Rico, skies cleared out as a drier air mass moved
over that region.

The most recent satellite-derived precipitable water value product
shows a moisture gradient over the region. First, below normal
moisture values are observed along western Puerto Rico and the
Atlantic waters, but plenty of moisture lingers in the Caribbean in
the vicinity of Saint Croix. In fact, the high resolution models
show that showers will continue to stream across this region, so
ponding of water on roadways is possible today. Shower activity will
be possible, but not as much across Saint Thomas, Vieques and
Culebra.

For Puerto Rico, the wind flow at the mid and upper levels is now
zonal, as a jet stream passes just north of the region, and the
upper level trough departs toward the east. Most of the moisture
should remain east of the region today, but there is enough to
trigger showers in the afternoon along the interior and southwestern
Puerto Rico. The showers are not expected to be as widespread as the
previous days, but since the soils are so saturated and rivers are
running high, flooding and mudslides will remain possible in these
areas.

The slight improvement in the weather conditions will not last long.
An area of moisture associated with the trough that affected the
area earlier this week and another one approaching from the Lesser
Antilles will combine to increase moisture above climatological
levels on Sunday and Monday. First, showers will move from the east,
affecting the Virgin Islands and eastern Puerto Rico during the day,
and then additional convection will kick in in the afternoon across
the interior and western Puerto Rico. Again, the likelihood of
flooding, rapid river rises, and mudslides will be elevated.

Also on Monday, temperatures at 925 mb will be two standard deviation
above normal, meaning that it should be hot too. It is possible that
the cloud coverage may prevent temperatures for rising too much, but
coastal areas experiencing enough sunshine could see heat indices
above the 100 degree mark.

.LONG TERM...Tuesday through Saturday...

A wet and unstable weather pattern is expected to return in the long-
term forecast. A surface high pressure across the central Atlantic
and a surface low over the western Atlantic will induce east-
southeast winds across the CWA. Consequently, this wind pattern will
promote warmer temperatures over the islands and pull tropical
moisture into the area. Precipitable water content is expected to
remain within the range of 1.9 to 2.2 inches. These values exceed
the 90th and 99th percentiles of the climatological normal,
indicating well above-normal moisture levels for this time of year.

In terms of instability, an upper-level trough is expected to deepen
throughout the week, inducing an inverted surface trough west of
Puerto Rico. These features will gradually progress eastward during
the week, sustaining unstable weather conditions capable of
generating deep convective activity. The likelihood of convective
activity will be highest during afternoon hours as high moisture
content and instability combine with surface heating and local
effects.

Soils are expected to remain somewhat saturated by Tuesday due to
rains from previous days, with rivers still experiencing elevated
streamflows. Consequently, the flood risk will remain elevated to
significant through at least Friday, particularly during afternoon
hours. Quick river rises, river flooding, and landslides are also
possible, primarily across Puerto Rico. In the US Virgin Islands,
minor flooding with brief periods of excessive runoff is possible
each day of the week.


&&

.AVIATION...
(06z) TAFS

Mainly VFR conditions expected. SHRA will stream across the Atlantic
waters and passages, occasionally reaching TSJU and the USVI
terminals. After 17Z, additional activity is expected in the
vicinity of TJPS. All this activity may result in brief periods of
reduced VIS and low ceilings. Mountain obscuration is expected for
the western Cordillera Central. Winds are from the NE at 5-12 kts.

&&

.MARINE...

Gentle to moderate northeasterly wind flow will continue to prevail
across the local waters through at least early the next workweek,
becoming light to gentle from the east southeast on Tuesday. A small
northeasterly swell will move across the Atlantic waters through the
weekend. However, seas will remain less than 5 feet for the most
part.

&&

.BEACH FORECAST...

Although there is no high rip current risk statement, life-
threatening rip currents remain possible in the surf zone,
especially along north-facing beaches of the local islands. Please
remember to heed the advice of the local beach patrol and flag
warning systems.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
450 AM AST Sun Apr 21 2024

.SYNOPSIS...

Suspended Saharan dust will be present early this week, promoting
hazy skies. However, this will be short-lived as a moist and
unsettled weather pattern will prevail throughout the week.

&&

.SHORT TERM...Today through Tuesday...

Persistent shower activity has been observed across Saint Croix and
the northern coast of Puerto Rico all night long. However, rainfall
rates were not that strong, and accumulations generally remained at
around 1.5 inches for Vega Baja and below one inch elsewhere. The
most recent satellite-derived precipitable water imagery show plenty
of moisture in the vicinity of Saint Croix, but drier air to the
northwest of Puerto Rico. This moisture field is associated with a
surface trough that will gradually move over the region, once again
increasing the frequency of showers. The activity should increase in
the afternoon or evening hours, first spreading into St. Thomas and
St. John, then Vieques, Culebra and eastern Puerto Rico. Also,
showers are expected to develop due to local effects over the
eastern interior and another cluster in the southwest.

The unsettled weather pattern persists on Monday as the moisture
field advances into the region. At the same time, a surface high
pressure migrating toward the northeast just north of the region
will make the winds shift from the southeast at the surface, and
from the south from 900 to 600 mb. With all that moisture and under
a southern wind flow, heat indices will increase in areas that are
not under the cloud shield of the trough (likely coastal areas of
Puerto Rico and Saint Croix). Aside from the heat, the main focus
will be the rain again, since additional showers and thunderstorms
are anticipated. The light wind flow will make the activity to
develop along the Cordillera Central, then spreading mostly toward
the north, and possibly moving into the San Juan metro area. Soils
in the interior municipalities are saturated and rivers are running
high , so another round of at least urban flooding is likely.

Saharan dust will follow this rain event on Tuesday. So far, the
aerosol models show that the denser cloud of dust will remain over
the Caribbean waters, and reaching St. Croix, where hazy skies and
periods of reduced visibilities are possible. Elsewhere, grayish
skies will be possible at times, but with less concentration of dust
in general.

.LONG TERM...Wednesday through Sunday...

Traces of suspended Saharan dust particulates will still be
present on Wednesday, leading to some hazy skies, especially
during the morning hours. For the rest of the week, a wet and
unstable weather pattern will persist. A series of short-wave
troughs will move over the local islands throughout the week,
creating favorable dynamical conditions aloft for shower and deep
convective development. This will maintain 500 mb temperatures
between -6 and -7 degrees Celsius and steep lapse rates for most
of the long-term forecast. Meanwhile, elevated moisture levels
will be present at all levels, with columnar moisture well above
normal for this time of year.

Most indicators, including precipitable water and the GDI (Galvez-
Davidson Index), suggest that Friday will have the highest chance
of thunderstorms and heavier showers. This is when low-level
moisture convergence and steep lapse rates will be at their
maximum. Friday also poses the greatest potential for widespread
urban and small stream flooding, as well as localized flash
flooding, although similar risks will also exist on previous days
with less areal coverage. As mentioned earlier, river streamflows
will remain elevated, especially those across interior Puerto
Rico. Therefore, any additional rainfall could lead to quick river
rises in these areas. Additionally, saturated soils will enhance
runoff, increasing the risk of landslides in steep terrain.

Weather conditions will gradually improve by the weekend. However,
lingering moisture, coupled with diurnal heating and local effects,
will continue to foster afternoon convection across interior
portions of Puerto Rico and downwind of the smaller islands.


&&

.AVIATION...
(06z) TAFS

SHRA will continue in the vicinity of TISX, with period of reduced
VIS and low ceilings. Additional SHRA will develop after 17Z for the
Cordillera Central, resulting in mountain obscuration. After 21Z,
the frequency of SHRA will also increase around TJSJ and TIST. Winds
will be from the ENE at 9-14 kts.


&&

.MARINE...

Gentle to moderate northeasterly wind flow will continue to prevail
across the local waters through at least early this week, becoming
light to gentle from the east southeast on Tuesday. A small
northeasterly swell will move across the Atlantic waters through the
weekend. However, seas will remain less than 5 feet for the most
part.

&&

.BEACH FORECAST...

Moderate rip current risk will persist today, indicating the
possibility of life-threatening rip currents in the surf zone,
especially along north-facing beaches of the local islands. Please
remember to heed the advice of the local beach patrol and flag
warning systems.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
414 AM AST Mon Apr 22 2024

.SYNOPSIS...
Numerous showers moved across eastern Puerto Rico and the
Caribbean waters during the night hours, triggering some flooding.
The wet pattern is expected to stretch into the end of the
workweek, with some improvements Saturday onward. The risk for
flooding will remain elevated. In the meantime, Saharan dust will
arrive on Tuesday, with hazy skies in some areas.

&&

.SHORT TERM...Today through Wednesday...

It was a very active night, particularly for the eastern coastal
area of Puerto Rico. While heavy showers that affected St. Croix
subsided, shower activity shifted to the eastern portions of Puerto
Rico. Several rounds of showers resulted in excessive runoff high in
the mountains of Naguabo, causing water levels at Rio Blanco to rise
quickly. A Flood Warning was issued, and shortly afterward, the USGS
river sensor indicated Moderate Flood Stage later in the night.
Additionally, a convergence line developed, affecting northeastern
municipalities. Flood Advisories were issued for municipalities from
Luquillo westward through Bayamon. In these areas, several rivers
experienced rapid rises in water levels, with at least four rivers
reaching Action stage according to USGS river sensors. The
convergence line persisted, exacerbating the situation across Loiza,
northern Canovanas, and northwestern Rio Grande. Therefore, a Flash
Flood Warning was also issued. Meanwhile, in the Caribbean, a line
of strong thunderstorms developed and is now approaching
southeastern municipalities. Expect shower and thunderstorm activity
across southeastern municipalities during the early morning hours."

This wet and unstable weather pattern is caused by a surface short-
wave trough associated with the remnants of a frontal boundary. The
Blended Total Precipitable Water (TPW) Percent of Normal indicates
moisture levels exceeding 145% of the climatological normal from the
Leeward Islands through the local area. Therefore, moisture
advection will persist today, promoting periods of moderate to heavy
showers, particularly over windward sections of Puerto Rico and USVI
during the morning hours and across interior and northwestern Puerto
Rico as moisture availability combines with diurnal heating.

No relief is expected for the rest of the short-term forecast as
some troughing aloft will maintain instability at upper levels. The
day with the least showers could be anticipated by Tuesday as an
area of suspended Saharan dust fills the area, which could somewhat
inhibit shower activity. However, in some areas, this won't be
enough to suppress showers; in fact, it could even promote frequent
lightning activity due to the presence of Saharan dust. This won't
last long, as high moisture content and favorable dynamics will
persist, maintaining elevated flooding risk across the islands.
Soils are saturated, which will promote excessive runoff easily with
potential landslides, while river streamflows are elevated with the
potential of overflowing with any strong shower activity. Therefore,
continue to monitor this forecast and pay attention to any
advisories/warnings that we could issue.

.LONG TERM...Thursday through Monday...

The wet pattern will not give way by the end of the workweek.
Moisture associated with an old frontal boundary will reach the
islands, triggering another round of showers and isolated
thunderstorms. At the same time, a deep layered trough moving east
of the United States will cause the winds to shift from the south
at the mid and upper levels, while winds will remain from the east
steered by a surface high pressure over the central Atlantic. The
southerly flow will bring a moist column into the region, while a
short wave trough (the type that increase instability aloft) will
approach the region. These factors should combine to generate more
rainfall activity. Since it has been raining for a couple of days
now, rivers will remain high and soils saturated, hence the risk
for urban and small stream flooding will be elevated.

A change in the pattern will begin on Saturday. A broad surface
high pressure exiting the eastern seaboard will push a drier air
mass into the region...finally. Winds will become more northerly,
so temperatures will cool down a little too. The probability of
precipitation decreases Saturday onward, although with some
showers due to local effects still possible. This drier pattern
should stretch into early next week.


&&

.AVIATION...
(06Z TAFs)

Although fairly active night, mostly VFR conditions can be expected
to prevail across all terminals through the forecast period. Brief
MVFR/IFR due to reduced VIS and CIG are possible at TJSJ thru 22/14z
due to SHRA, and at TJBQ/TJSJ, aft 22/17z along with mtn
obscuration. ENE winds at 10-15 kt mostly aft 22/14z. with higher
gusts near showers.

&&

.MARINE...
A surface high pressure north of the area will continue to yield a
moderate northeasterly wind flow through at least Monday. Winds are
expected to become from the east southeast on Tuesday as a surface
trough prevails across the northeast Caribbean. Showers and isolated
thunderstorms will continue to affect the local waters today.

&&

.BEACH FORECAST...
Breaking waves around 4 feet will maintain the risk of rip
currents moderate for the north facing beaches of Puerto Rico and
for some beaches in Culebra. Elsewhere, the risk of rip currents
will remain low.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
421 AM AST Tue Apr 23 2024

.SYNOPSIS...
A surface trough continue to impact the local islands, bringing
periods of showers and thunderstorms. Slight concentrations of
Saharan dust are expected today as well, so skies could be hazy.
The wet weather pattern will persist through the end of the
workweek, but drier conditions are anticipated late in the weekend
and early next week.

&&

.SHORT TERM...Today through Thursday...

The axis of the surface trough was located just west of Puerto Rico
during the early night hours. However, the most active part of the
trough was situated over the USVI, Vieques, and Culebra. Heavy
showers and strong thunderstorms pulsed throughout the night across
this region, with some reaching eastern portions of Puerto Rico.
Despite this area of activity, the night was much calmer than the
previous night. The greatest rainfall accumulations estimated by the
radar were over western and eastern St. John and Puerto Rico,
respectively, with slightly above 1 inch each. Satellite and radar
data indicate an elongated convergence zone promoting heavy showers
persisting west of St. Croix. As this active area is advected
westward, expect cloudy skies and showery weather across the eastern
third of Puerto Rico during the morning hours, with some localized
areas possibly experiencing heavy showers.

According to TAFB surface analysis, the axis of the surface trough
is expected to persist over and near the CWA through at least the
end of the week. This is attributed to the deepening and approach of
a mid-level short-wave trough and surface frontal boundary from the
west, which will combine with the surface trough that has been
impacting us over the last day or so. This weather pattern will
maintain unsettled conditions for the rest of the short-term
forecast. The 1000-500mb thickness will gradually decrease
throughout the week, with steep 850-700 mb lapse rates.
Additionally, this setup will promote enhanced moisture convergence
across the region. Model guidance suggests precipitable water
content will remain within the range of 1.9 to above 2.0 inches for
most of the period, with slightly lower amounts across the eastern
half of the CWA by Thursday afternoon onwards.

USGS river sensors still indicate that most rivers over the eastern
half of Puerto Rico are exceeding the 75th percentile, with half of
them surpassing the 90th percentile or well above normal. Soil
saturation is also high, increasing the potential for excess runoff
and landslides in steep terrain. Therefore, the flood risk over the
eastern half of Puerto Rico will remain elevated for the rest of the
short-term forecast, as any additional rainfall could exacerbate
these factors. For the rest of the area, a limited to elevated
flooding risk will persist. Suspended Saharan dust particulates will
be present, promoting hazy skies in areas with limited shower
activity.

.LONG TERM...Friday through Tuesday...

As a shortwave trough digs into the western Caribbean, high clouds
are expected to get established over Puerto Rico and over the Virgin
Islands. At the surge, a high pressure over the central Atlantic
drives the trade winds from the east at speeds below 15 knots.
Moisture from a surface trough/old frontal boundary will linger into
the region, maintaining that pattern of showers reaching the region
at times. The moisture will finally be pushed south of the islands
late on Friday and early Saturday, as a high pressure exits the
eastern coast of the United States. This feature will push a drier
air mass into the islands, with precipitable water values falling to
near normal values on Saturday, and below normal all the way into
Tuesday. Winds will be from the northeast all this period, with a
more northerly component at times. It will be brisk too, with speeds
at 15 to 20 mph, and stronger gusts. In reality, is not going to be
completely dry, since some showers will still develop over the
Atlantic, reaching the USVI and northeastern PR at times, and some
showers will still develop in the afternoon over southwestern Puerto
Rico. However, they will not be as widespread or strong as the one
being experienced lately.


&&

.AVIATION...
(06Z TAFs)

Mainly VFR conditions will prevail during the morning. SHRA ovr the
waters could promote MVFR conds thru 23/14z across USVI terminals.
Afternoon TSRA/SHRA could result in brief MVFR/IFR conditions,
mainly across PR terminals btwn 23/17-23z. After that, SHRA may
affect USVI terminals and TJSJ. HZ due to Saharan dust, but VSBY
should remain P6SM. Surface winds will remain from the east-
southeast at 5 to 10 kt but will then range between 10- 15 knots
with higher gusts after 23/13z.

&&

.MARINE...
A surface trough crossing the islands will yield winds from the
southeast today. Showers and thunderstorms will continue to affect
the local waters today. A small northwesterly swell will arrive late
Wednesday and Thursday. Another surface trough will shift the winds
from the east by Wednesday, before switching from the northeast on
Saturday under the influence of a surface high pressure over the
western Atlantic.


&&

.BEACH FORECAST...
Breaking waves of around 3 feet will maintain the risk of rip
currents generally low. The risk will become moderate again on
Wednesday night.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
429 AM AST Wed Apr 24 2024

.SYNOPSIS...

The influence of a surface trough will continue to impact the
local weather conditions. Another active afternoon is anticipated
due to the combination of the surface trough, diurnal heating,and
local effects. Winds are forecast to be light today, promoting
slow-moving showers and thunderstorms. With the expected weather,
the potential for urban and stream flooding remains elevated
today.

&&

.SHORT TERM...Today through Friday...

Throughout the overnight hours, satellite and radar detected a band
of showers and cloud coverage stretching from the Caribbean waters
to the Atlantic waters, primarily between eastern Puerto Rico and
the USVI. These showers moved slowly, with the land breeze in
eastern Puerto Rico keeping them mostly over the waters. However,
some moderate to strong showers brushed coastal areas at times.
Eastern coastal portions of Puerto Rico received up to 1.5 inches of
rainfall, with the highest amounts observed in Fajardo and Ceiba. A
similar pattern is expected to continue during the morning hours,
with localized areas across windward coastal sections experiencing
showers that could lead to ponding of water on roads and in poor
drainage areas. In areas with little to no rain, hazy skies will
prevail as suspended Saharan dust particulates continue to move in.
The heat risk for today will be limited across western and northern
coastal areas of Puerto Rico.

The axis of the surface trough remains nearby, with light east-
southeast winds persisting, influenced by an approaching frontal
boundary from the northwest. These winds continue to advect warmer
temperatures across the region. Therefore, another active afternoon
is anticipated due to the combination of the surface trough,
enhanced diurnal heating, marginal instability aloft, and local
effects. Gusty wind conditions may be observed, particularly in the
vicinity of collapsing thunderstorms. However, winds will be mostly
light, which could promote slow-moving showers and thunderstorms.
This will increase the risk of flooding as rainfall accumulations
are enhanced by this factor. Activity will be confined mostly over
interior Puerto Rico, gradually moving west and north as the
afternoon progresses. Heavy showers can also be observed across the
San Juan metro area and downwind of the smaller islands.

By Thursday and Friday, the surface perturbation is expected to have
moved away from the area. However, a mid-level short-wave trough,
along with the aforementioned frontal boundary, will cross the
northeastern Caribbean through the end of the week, maintaining or
even enhancing unstable conditions across the region. Moisture
levels will also remain above normal throughout this period.
According to the GFS Enhanced Galvez-Davison Index, divergence aloft
will peak between Thursday evening and early Friday, with maximum
values expected over the Atlantic waters between Hispaniola and
Puerto Rico. The uncertainty lies in the location of the highest
divergence aloft and whether it coincides with surface heating
during peak daytime hours or remains mostly over the local waters.

Nevertheless, expect wet and unstable weather conditions for the
remainder of the short-term forecast, characterized by alternating
periods of heavy showers and isolated to scattered thunderstorms.
Consequently, the risk of flooding will remain elevated, with the
potential for urban and small stream flooding, along with localized
flash flooding and landslides. Gusty wind conditions and frequent
lightning cannot be ruled out, particularly with the strongest
activity.

.LONG TERM...Saturday through Wednesday....

Lingering moisture from a surface trough will continue to produce a
pattern of passing showers on Saturday, especially during the
morning hours. By later in the afternoon, this moisture will
gradually be pushed south of the local region, as a surface high
pressure exits the eastern coast of the United States. This surface
high will push drier air into the local area and will promote mainly
fair weather conditions for most of the long-term period. The drier
airmass will lower the precipitable water values to around 1.20
inches from Saturday through Tuesday. Moderate to fresh northeast
winds between 15 to 20 mph with higher gusts are expected in
response to the surface high as well. Despite of the drier air
filtering into the local area, there is the chance for shower
development over the local waters at times. These showers may reach
the U.S. Virgin Islands and portions of Puerto Rico. In addition,
afternoon convection is possible across the southwestern portions
of Puerto Rico each afternoon due to the combination of daytime
heating and local effects. Wednesday will be a transition day from
a dry into a much wetter pattern. A field of moisture is expected
to reach the local area from South America increasing the
potential for heavy showers and thunderstorms across the region.
Daytime temperatures are expected to remain in the mid 80s along
the coastal and urban areas of Puerto Rico and the U.S. Virgin
Islands, and in the low 80s across the higher elevations. Heat
indices will stay in the mid to upper 90s.

&&

.AVIATION...
(06Z TAFs)

Expc mainly VFR conditions across all terminals through the forecast
period. However, areas of SHRA and SCT TSRA this aftn could produce
tempo MVFR/IFR conds and mtn obsc, particularly ovr TJBQ aft 24/17z.
VCTS/SHRA at TJSJ/TJPS for the most part. ESE winds reaching speeds
of up to 8-13 knots, accompanied by higher gusts and sea breeze
variations aft 24/13z. HZ due to Saharan dust, but VSBY should not
drop more than 7 miles.


&&

.MARINE...

A small northwesterly swell is expected to arrive later tonight into
Thursday. Showers and thunderstorms will continue to affect the
local waters for the next few days. Another surface trough will
strengthen the easterly winds today and Thursday, before becoming
northeast on Saturday under the influence of a surface high pressure
moving off the eastern coast of the United States.


&&

.BEACH FORECAST...

Breaking waves of around 3 feet will maintain the risk of rip
currents generally low today. However, will become moderate again
tonight for the northern beaches of the local islands.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
512 AM AST Thu Apr 25 2024

.SYNOPSIS...

Wet and unstable weather conditions are expected to prevail for
the next few days with limited to elevated risks of flash
flooding, urban and river flooding, and landslides mainly over the
interior, western, and northern Puerto Rico, as well as the San
Juan metro area. A slight improvement on weather condtions is
expected by Saturday night into Sunday as drier air filters into
the local area.

&&

.SHORT TERM...Today through Saturday...

Isolated to scattered showers affected the eastern third of Puerto
Rico and smaller islands during the night hours. However, most of
the activity remained over the Caribbean waters. Radar estimates
indicated up to 0.60 inches of rainfall fell mainly over and near El
Yunque. Similar activity is expected for the rest of the morning
hours over windward coastal areas.

According to the Tropical Analysis and Forecast Branch (TAFB)
surface analysis, the axis of the surface trough that has been over
the CWA for the past few days will finally move northwestward today.
However, plenty of columnar moisture, combined with diurnal heating
and local effects, along with marginal instability aloft, will
promote another active afternoon. Model guidance suggests that the
bulk of the activity will be clustered a bit further north than the
previous day steered by southeast to east-southeast winds.
Nonetheless, heavy showers and thunderstorm activity will generally
be observed in already saturated soils and areas with elevated
streamflows.

While the overall wet and unsettled weather pattern will persist for
the remainder of the short-term forecast, some changes have been
suggested by the latest model cycle for Friday and Saturday. Late
tonight through early Friday, we could observe a slight decrease in
showers, mostly across the eastern CWA, as a slot of slightly drier
air moves in. However, this respite won't last long as the pre-
frontal trough currently affecting the Dominican Republic will
gradually move over the local area by Friday, increasing low-level
instability and moisture convergence over the region. Meanwhile, a
mid-level short-wave trough will strengthen and pass over the
northeastern Caribbean, further enhancing the potential for deep
convective activity. Therefore, another afternoon with widespread
activity is expected on Friday.

By Saturday, previous model cycles indicated a drying trend, which
was expected to limit the areal coverage of convective activity
across the area. However, the latest model cycle now suggests a
prolongation of above-normal moisture across the islands. The GFS
Galvez Davison Index suggests the potential for isolated to
scattered thunderstorms and heavy rainfall on Saturday afternoon,
delaying the transition to a more stable weather pattern.
Additionally, cold air advection at mid-levels will be high, with
500 mb temperatures falling between -8 and -9 degrees Celsius. This
will enhance low- to mid-level lapse rates and increase the
potential for strong thunderstorms capable of producing frequent
lightning and gusty wind conditions.

Overall, expect a wet and unstable weather pattern throughout the
short-term forecast, with limited to elevated risks of flooding and
lightning across the area, particularly over interior, western, and
northern Puerto Rico, as well as the San Juan metro area. Urban and
river flooding, flash flooding, and landslides will continue to
impact areas already affected in the past week. Please continue to
monitor the forecast in the next few days and pay attention to any
advisories or warnings that our office may issue.

.LONG TERM...Sunday through Thursday...

A strong surface high pressure moving off the eastern coast of the
united states, is expected to promote moderate to locally fresh
northeast winds at the beginning of the long-term period. The latest
model guidance have changed, delaying the departure of the
moisture from the local area. However, by Sunday remnant moisture
from a surface trough and old frontal boundary will be pushed
south of the region, improving gradually the local weather.
Variable weather conditions are expected from Sunday through
Tuesday, with passing showers over the east coast of Puerto Rico
and the U.S. Vrigin Islands. Then, followed by afternoon
convection across the southwest portions of PR due to the
combination of daytime heating and local effects. Precipitable
water values will remain between 1.40 to 1.50 inches through
Tuesday night. By Wednesday, a patch of very dry air will filter
into the region, limiting the potential of shower activity across
the islands. However, this fair weather pattern will not last
long due to the arrival of a big field of moisture pulled from
South America toward the eastern Caribbean region on early
Thursday. A wet and unsettled pattern is anticipated with an
elevated potential of showers and thunderstorms across the local
area. The general wind flow will be from the northeast then
veering from the east southeast by Thursday. Daytime temperatures
will remain in the mid 80s along the coastal and urban areas of
Puerto Rico and the U.S. Virgin Islands, and from the mid to upper
70s across the Cordillera Central.

&&

.AVIATION...
(06Z TAFs)

Expc mainly VFR conditions across all terminals through the forecast
period. However, areas of SHRA and SCT TSRA this aftn could produce
tempo MVFR/IFR conds and mtn obsc, particularly ovr TJBQ/TJSJ aft
25/17z. VCTS/SHRA at TJPS for the most part. ESE winds reaching
speeds of up to 8-12 knots, accompanied by higher gusts and sea
breeze variations aft 25/13z.

&&

.MARINE...

A small northwesterly swell is expected to spread across the local
waters today. Showers and thunderstorms will continue to affect the
local waters for the next few days. Another surface trough will
strengthen the easterly winds from today into Friday, before
becoming northeast on Saturday under the influence of a surface high
pressure moving off the eastern coast of the United States.

&&

.BEACH FORECAST...

Breaking waves of around 3 feet will maintain the risk of rip
currents generally moderate for the northern beaches of the local
islands.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
417 AM AST Fri Apr 26 2024

.SYNOPSIS...

Another active day is expected across the local area due to an
approaching mid-to-upper-level trough. Above-normal moisture in
combination with daytime heating and local effects will enhance
the potential for heavy showers and thunderstorms, mainly across
the central interior and western Puerto Rico. There is a limited
to elevated risks of flash flooding, urban and river flooding,
and landslides for the mentioned areas. We encourage citizens to
stay informed and monitor our forecast for additional updates.

&&

.SHORT TERM...Today through Sunday...

Puerto Rico and the U.S. Virgin Islands experienced calm weather
conditions, with a mid-to-upper-level cloud layer moving across
them. Our Doppler Radar detected most rain over the waters, with
some moving mainly across southeast Puerto Rico. Low temperatures
across the coastal areas ranged around the mid-70s and in mountains
and valleys around the mid-60s. The prevailing winds are now more
from the east, though land breeze fluctuations developed overnight.

We anticipated an increase in low-level moisture as the front/shear-
line moves near PR and eventually the USVI. The latest model
guidance suggests an increasing instability trend due to an
approaching mid-to-upper-level trough accompanied by a jet stream.
This weather pattern could lead to deep convective activity,
particularly during the afternoons, when diurnal heating, local
topography, and sea breeze may play an additional role, enhancing
the convection. We strongly encourage citizens to stay informed and
monitor our forecast for further updates, which will empower you to
plan and prepare effectively.

Today, we expect calm weather in the morning, with an increase in
showers and thunderstorms by early this afternoon. The strongest
thunderstorms are possible across the western interior and western
PR. Showers will then increase across the Virgin Islands by late
this afternoon into the evening and early Saturday morning as a
plume of moisture kicks in, resulting in showery weather, with
possible isolated thunderstorms moving inland from the surrounding
waters. Eastern PR may observe unsettled weather conditions from
early Saturday morning to afternoon. Winds will shift from the NE,
shifting the focus of strong afternoon convection across the
southwest quadrant and southern slopes of PR, while moisture may
erode over the Virgin Islands by Saturday afternoon. For that
reason, the risk of flooding remains elevated across most islands,
especially during the afternoons today and Saturday. It's crucial to
be cautious and aware of these potential risks.

We expect a solid surface high pressure moving off the eastern coast
of the USA, promoting breezy northeast winds across the Northeast
Caribbean around Sunday. This wind flow introduces some
discrepancies in our model guidance regarding the final position of
the plume of moisture. Therefore, our model guidance has moderate to
high uncertainty about how much moisture may pool over the islands
on Sunday if it remains over them or further south across the
Caribbean Sea. Regardless of the discrepancies, unstable and
possibly showery weather remains possible that day.

.LONG TERM...Monday through Friday...

A strong surface high pressure located over the eastern coast of the
United States will promote a northeasterly wind flow from Monday
through Wednesday. As this feature moves from the western to the
central Atlantic winds are expected to veer from a more easterly
component through the rest of the long-term period. Previous model
runs indicated a drying trend for the beginning of the workweek,
however, the latest model guidance now suggests a prolongation of
above-normal moisture across the islands. The precipitable water
content values are between 1.60 to 1.80 until Wednesday, then
increasing up to 2.20 inches through the rest of the period. A vast
moisture field coming from South America to the eastern Caribbean
will help to enhance the shower and thunderstorm activity across the
islands. This wet and unstable weather pattern will promote rainfall
activity everyday across the area, especially over portions along
the Central Cordillera, eastern, and western portions of Puerto
Rico. The U.S. Virgin Islands will also experience moderate to
locally heavy showers by the end of the period. With the expected
weather scenario limited to elevated risks of urban and river
flooding, flash flooding, and landslides will continue to impact
areas already saturated by the previous days/week rainfall activity.
Daytime temperatures are expected to stay in the mid 80s along the
coastal and urban areas of Puerto Rico and the U.S. Virgin Islands,
and from the upper 70s to low 80s across the interior.

&&

.AVIATION...
(06Z TAFs)

Mainly VFR conditions expected to prevail across all terminals.
However, SHRA/TSRA expected to develop over the western interior may
lead to mtn tops obscd and MVFR cigs in and around TJBQ/TJPS btw
26/18z-22z. Also, after 26/23z showers en route from the Leeward
Islands/Atlc waters may cause brief -SHRA or MVFR conds at
TISX/TIST/TJSJ thru the rest of the overnight hours. East winds up
to 12 kt with sea breeze variations aft 26/14z, bcmg ENE around
26/21z across most terminals.

&&

.MARINE...

A small northwesterly swell will continue to spread across the local
waters through today. Showers and thunderstorms will continue to
affect the local waters for the next several days as lingering
moisture from a surface trough/old frontal boundary remains over the
local area. Winds will prevail from the east and becoming northeast
on Saturday under the influence of a surface high pressure moving off
the eastern coast of the United States.

&&

.BEACH FORECAST...

Breaking waves of around 5 feet will maintain the risk of rip
currents moderate for the northern beaches of the local islands.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
400 AM AST Sat Apr 27 2024

.SYNOPSIS...

Unsettled weather conditions are expected to prevail today, with an
elevated risk of flooding, especially for the interior and
southwestern Puerto Rico. Some improvement is anticipated for the
first couple of days of the workweek, but the pattern will turn wet
again after Tuesday, with additional periods of showers and
thunderstorms. Marine and coastal conditions are expected to
deteriorate Monday onward as a northerly swell arrives.

&&

.SHORT TERM...Today through Monday...

Isolated to scattered showers affected the local waters of Puerto
Rico and the U.S. Virgin Islands overnight. Some of these showers
reached the eastern coast of Puerto Rico, leaving minor
accumulations over Humacao, Las Piedras and San Lorenzo. Similar
weather conditions are expected to persist through at least the mid-
morning hours. Low temperatures were observed in the mid to upper
60s across the mountains, and around the mid 70s along the coastal
and urban areas. Light winds from the east prevailed through most of
the night.

Another active day is anticipated as a plume of moisture moves into
the region, promoting moderate to locally heavy showers and isolated
thunderstorms. The latest model guidance are showing an increase in
moisture content by the mid-morning hours through the afternoon with
precipitable water values ranging from 1.90 to 2.20 inches. This
moisture content in combination with diurnal heating, local
orographic effects, and sea breeze may lead to deep convective
activity over Puerto Rico. Therefore, the rainfall risk is elevated
today for the eastern, central interior and southwestern portions of
Puerto Rico, including the San Juan metro area. Due to previous
rains, soils are very saturated and additional rains could lead to
flash flooding, river rises, and mudslides. We encourage residents
and visitors to stay aware and monitor the weather forecast in your
location to plan your weekend accordingly.

A strong surface high pressure located over the Carolinas in the
U.S. eastern coast will promote moderate northeast winds today.
Winds are expected to increase on Sunday, resulting in breezy
conditions during the first days of the week. Model guidances
continue to show an above-than-normal moisture through the rest of
the period, with a slight improvement on Monday. Prepare for a wet
and unstable weather pattern to persist for the next several days.

.LONG TERM...Tuesday through Saturday...

A high pressure system at the lower levels of the atmosphere will
drive the winds from the east at the surface, and from the northeast
a little bit aloft. This feature will maintain the moisture trapped
in the lower levels of the atmosphere. In general, Tuesday looks
like the driest day of the forecast period, but moisture will still
remain at seasonal levels, triggering convection in the interior and
southwestern Puerto Rico.

The pattern will turn wet again for the rest of the workweek as yet
another mid and upper level trough digs into the western Caribbean.
This trough will pull plenty of moisture from the Caribbean Sea into
the local islands, and precipitable water values will be above
normal. On Wednesday, the steering flow will be from the southeast,
so local effects should trigger for the interior, north and
northwest of Puerto Rico, as well as around the Virgin Islands and
local waters. Then, on Thursday, as the trough further approaches,
the steering winds will collapse, with very light winds anticipated.
Additionally, the mean flow will be from the southwest, so activity
could switch focus for the eastern interior, the San Juan metro
area, and then the Virgin Islands.

One thing that could delay the development of rain, however, is that
if a thick cloud layer get established, then local effects will be
milder. Also, temperatures could be below normal for a change,
except for the southern coast of Puerto Rico, where values are still
expected to reach the low 90s. On the other hand, if there are
breaks of sunshine, then the risk for showers and thunderstorms will
be elevated, likely producing urban and small stream flooding, water
surges along rivers, as well as mudslides.

By Friday, the influence of the mid and upper level trough
diminishes, but a surface reflection remains, maintaining enough
moisture, and a light wind flow from the northeast. More moisture
will also be added into the mixture from another trough approaching
the eastern Caribbean from the east. Thus, another active afternoon
is anticipated for the interior of Puerto Rico, with activity then
spreading toward the coastal areas. Since some drier air will filter
at the mid and upper levels, temperatures will warm up again to more
seasonal values, reaching the mid and upper 80s, and even the low
90s.

On Saturday, the pressure gradient begins to recover as a surface
high pressure exits the eastern coast of the United States. The
winds will be around 10 knots, and out of the southeast. Lingering
moisture around the northeastern Caribbean will maintain a showery
pattern, with another active afternoon and an elevated risk for
flooding and mudslides.

&&

.AVIATION...
(06z TAFs)

Mainly VFR conds expected across all terminals through the forecast
period. However, areas of SHRA/TSRA could produce tempo
MVFR/IFR conds and mtn obsc, mainly over TJPS/TJBQ aft 27/14z. VCSH
expected at TJSJ/TIST/TISX terminals after 27/13z. ENE winds btw 9
to 14 knots with by higher gusts and sea breeze variations aft
27/13z.

&&

.MARINE...

A small northwesterly swell will continue to spread across the
local waters today into the rest of the weekend. Winds will
prevail from the east and becoming northeast today under the
influence of a surface high pressure moving off the eastern coast
of the United States. A northerly swell is anticipated to spread
across the local waters early next week deteriorating coastal and
marine conditions. Therefore, building seas are forecast from
Sunday into Monday across the offshore Atlantic waters, with seas
up to 7 feet. Small craft operators are urge to stay tune for
further advisories.

Additionally, showers and thunderstorms will continue to affect
the local waters for the next several days as lingering moisture
from a surface trough/old frontal boundary remains over the local
area.

&&

.BEACH FORECAST...

Breaking waves around 5 feet will maintain the risk of rip currents
moderate through Sunday along the north facing beaches of the
islands. A northerly swell will be arriving on Monday, increasing
the risk for these beaches to high through at least late
Wednesday.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
455 AM AST Sun Apr 28 2024

.SYNOPSIS...A surface high pressure over the western Atlantic will
promote northeasterly winds through at least Wednesday. Breezy
conditions are possible during the start of the workweek. Drier
air between a surface low over the north central Atlantic and the
surface high should reach the local area under the northeasterly
fetch. However, moisture content should remain at normal levels.
By mid-week onwards, instability and moisture levels increase
once again as an upper level trough lingers over the western
Atlantic and lighter east to southeast winds return. Life-threatening
rip currents are expected during the first part of the week.


&&

.SHORT TERM...Today through Tuesday...

Calm weather conditions prevailed across Puerto Rico and the U.S.
Virgin Islands, with quick passing showers over the local waters.
Low temperatures were observed in the range from the mid to upper
60s across the higher mountains and valleys, and from the low to mid
70s along the coastal areas. Breezy conditions prevailed across the
islands under a northeasterly wind flow.

Today, we expect mostly tranquil weather conditions during the
morning hours, with passing showers moving into the eastern coast of
Puerto Rico and the U.S. Virgin Islands at times. During the
afternoon hours, rainfall development is likely over portions of the
interior and southwest Puerto Rico due to lingering moisture of a
trough/frontal boundary in combination with daytime heating and local
effects. Precipitable water content values are in the range between
1.45 to 1.60 inches. Showers and isolated thunderstorms across the
mentioned sectors may result in flooding, river rises, mudslides and
isolated flash flooding. Soils are very saturated due to the rains
from the previous weeks, and any additional accumulations could
result hazardous. We continue to encourage citizens of Puerto Rico
and visitors to closely watch the weather conditions during the next
several days due to the potential for showers and thunderstorms each
afternoon.

A gradual improvement on weather conditions is anticipated over the
next few days, as a strong surface high pressure moves offshore the
eastern coast of the U.S. towards the Central Atlantic. This feature
will promote the entrance of a slightly drier airmass into the
region. Nonetheless, precipitable water content values should remain
within normal seasonal values. In response to the surface high,
moderate to fresh northeasterly winds will prevail today through at
least Tuesday. Then, shifting from the east on Wednesday. Despite of
some drier air across the region, shower development is anticipated
every afternoon across portions of the interior and southwestern
portions of Puerto Rico. However, rainfall accumulations should be
less compared to the previous days. High temperatures will remain in
the mid to upper 80s along the coastal and urban areas, and in the
mid to upper 70s along the mountains and valleys.

.LONG TERM...Wednesday through Sunday...

A more unstable and wetter pattern is expected to evolve during
the long term period as a mid-to upper-level trough develops and
remains nearly stationary over the west/southwestern Atlantic. By
Wednesday, the surface high pressure north of the area is
expected to weaken and in response winds are expected to veer from
the southeast, and become lighter through the rest of the period.
Meanwhile, old frontal boundaries and a restrengthening of the
surface low over the north central Atlantic will induce weak
troughs or perturbations across the northeastern Caribbean through
the end of the workweek. Steering winds will acquire a westerly
component and convective development with heavy showers are
possible over portions of the eastern interior, San Juan and
vicinity and over the USVI, particularly on Thursday and Friday.

Having said that and based on the latest guidance, all afternoons
through the long term period should be active with possible
flooding impacts and mudslides in areas of steep terrain across
Puerto Rico. For the USVI, an increase in the frequency of
showers and isolated thunderstorms is possible from Thursday
onwards. Heat indices across the lower elevations of the islands
could likely range between 102-106 degrees on Friday and Saturday
before the onset of afternoon convection.



&&

.AVIATION...

(06z) TAFS

Expect mainly VFR conditions expected to prevail across all terminals
through the forecast period. An increase in TSRA/SHRA this aftn may
produce brief MVFR cigs across TJPS aft 28/17Z. VCSH expected for
the TJSJ//TIST/TISX terminals after 28/13Z. Mountain obsc is
expected for the Cordillera Central from 28/13-22z. Breezy conds are
expected with winds out of the NE at 12-16 kts, and stronger gusts
after 28/13-14Z.


&&

.MARINE...

Light to moderate northeast winds will prevail today across the
regional waters, locally higher winds are expected due to sea
breeze variations across coastal areas. Winds are expected to
incrs from moderate to fresh tonight and continue through at
least late Tuesday as a surface high pressure moves off the US
East Coast. These increasing winds and a northerly swell spreading
across the local waters on Monday will further deteriorate seas
through at least mid-week. Small Craft Advisories are in effect
for the Atlantic waters and the Mona Passage.


&&

.BEACH FORECAST...

Short-period waves and onshore flow along the northern and
eastern beaches of the islands will promote a moderate risk of rip
currents today. A northerly swell arriving on Monday and stronger
winds will increase the risk of rip currents and promote life-
threatening rip currents from Monday through at least late
Wednesday. For more information and details about the latest
forecast please refer to the Surf Zone Forecast (SRFSJU).

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
434 AM AST Mon Apr 29 2024

.SYNOPSIS...

The surface high pressure over the western Atlantic will continue
to promote breezy northeasterly winds through at least midweek.
Drier airmass between a surface low over the north central
Atlantic and the surface high should reach the local area under
the northeasterly fetch, but moisture content will oscillate
between normal to above-normal values. As a consequence, light to
moderate showers with isolated thunderstorms cannot be ruled out
of the forecast. By mid-week onwards, instability and moisture
levels increase once again as a mid to upper level trough lingers
over the western Atlantic and lighter east to southeast winds
return.

&&

.SHORT TERM...Today through Wednesday...

Showers persisted through the early morning hours across portions of
northern and eastern PR and across the USVI. The Doppler radar
estimated between 1 and 2 inches of rain over Fajardo and Luquillo.
Minimum temperatures were from the mid-to-upper 70s across coastal
areas to the mid-60s across the higher elevations. Wind gusts were
up to 20-25 mph with the showers.

A strong surface high-pressure moving off the eastern coast of the
U.S. will move slowly towards the Central Atlantic during the next
few days. This system will bring slightly drier air to the region,
but the amount of precipitable water (PWAT) across the Caribbean
will still be within typical seasonal values. The surface high will
promote breezy conditions with moderate to fresh northeasterly winds
through at least Tuesday, then winds will shift from the east to
southeast and become light to moderate on Wednesday as the surface
high weakens. Therefore, we expect an advective pattern during the
nights with cooler air moving over warm waters and bringing showers
across portions of the USVI and along the north and eastern half of
PR, followed by diurnally induced afternoon convection over portions
of the interior and south/southwest PR each day.

Wednesday looks to be the wettest day of the short-term period as an
upper-level trough approaches the area from the west and an induced
surface trough develops over the northeastern Caribbean. This will
enhance shower and thunderstorm development across much of Puerto
Rico. Urban and small stream flooding and mudslides in areas of
steep terrain are possible.

High temperatures will remain in the mid-to-upper 80s along the
coastal and urban areas and in the mid-to-upper 70s along the
mountains and valleys. Minimum temperatures will range from the
upper 70s to low 80s across coastal areas to the mid-60s in the
higher elevations.

&&

.LONG TERM...Thursday through Monday...

The inherited forecast remains unchanged. Recent model guidance
suggests a mid-to-upper-level trough developing and staying
nearly stationary over the west to southwestern Atlantic, at least
through the long-term period. From Thursday onwards, expect the
winds to become lighter as the surface high pressure north of the
area continues to weaken. By Thursday, remnants of an old frontal
boundary will reach the island from the northeast and merge with a
trough or perturbation over the northeastern Caribbean. This will
lead to unstable and wetter weather conditions across Puerto Rico
and the U.S. Virgin Islands, with possible flooding impacts and
mudslides in areas of steep terrain across Puerto Rico. At this
time, Precipitable Water (PW) models suggest values above two
standard deviations and, therefore, above the normal
climatological levels for this time of the year. We anticipate
active afternoons during the long-term period, with possible
flooding impacts and mudslides in areas of steep terrain across
Puerto Rico. For the USVI, an increase in the frequency of showers
and isolated thunderstorms is possible from Thursday onwards.
Heat indices across the lower elevations of the islands could
likely range between 102 and 106 degrees on Friday and Saturday
before the onset of afternoon convection. Overall, an unstable and
wetter pattern is expected to evolve over the long-term.

&&

.AVIATION...
(06z) TAFS

Although VFR conds should prevail through most of the period, trade
wind SHRA may cause brief MVFR cigs at TJSJ/TIST/TISX/TJBQ at times.
Tempo MVFR conds are possible at TJPS btw 29/18-22z due to TSRA. NE
winds at 15-20 kt with stronger gusts near 30 kt during the day.

&&

.MARINE...

A sub tropical high pressure across the western Atlantic will
promote moderate to fresh trade winds through at least mid-week. We
expect hazardous seas for small craft operators due to confused seas
associated with the increasing winds and a northeasterly swell
spreading across the local waters.

&&

.BEACH FORECAST...

Short-period waves and onshore flow along the northern and
eastern beaches of the islands will promote a moderate risk of rip
currents to continue this afternoon and tonight. A northerly
swell arriving tomorrow (Monday) and stronger winds will increase
the risk of rip currents and promote life-threatening rip currents
through at least late Wednesday. For more information and details
about the latest forecast please refer to the Surf Zone Forecast
(SRFSJU) and the Coastal Hazard Message product (CFWSJU).