Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
523 AM AST Mon Apr 3 2023


.SYNOPSIS...

Scattered showers and breezy conditions are expected for Today
through Wednesday. Unsettled weather is forecast for Wednesday
night into Friday morning as a surface trough and TUTT moves over
the region. Thunderstorms are likely along with the chance of
localized flooding. There is a High Surf Advisory out for
northern facing beaches of Puerto Rico and a High Risk of Rip
Currents for several other areas.

&&

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

High pressure at the surface will prevail over the Central Atlantic
ocean and drive moderate to fresh easterly trade winds across the
local area. Areas of good moisture in the lower levels will be
interspersed with areas of rather dry air at 850 mb some of which
will be mixed down during the afternoons to produce clearing over
eastern Puerto Rico and the U.S. Virgin Islands. Scattered showers
generated during this period are unlikely to have strong impacts,
but overall moisture and shower frequency will increase beginning on
Tuesday.

Trofiness and upper levels will cause a cut off low to develop just
north of the area very late in the period and this will cause low
pressure at mid levels to form beneath it. This will lead into more
active weather late Wednesday night and into the long term period.

&&

.LONG TERM...Thursday through Monday...
A TUTT situated over the northern Caribbean will promote
unstable, rainy conditions for Thursday into early Friday. A
surface trough will pass through on Thursday in combination with
low 500 mb temperatures and a moist vertical column, making
thunderstorms a possibility throughout this time. Most of the
activity is forecast to be over the eastern half of the region.
Surface winds begin to veer early Friday morning, becoming a
prevailing east- southeasterly moist flow throughout the weekend.
During this time an increase of passing showers is expected to
arrive across eastern Puerto Rico during the morning hours
followed by afternoon convection, mostly affecting northwestern
Puerto Rico. During this time, high pressure continues to dominate
the Northern Atlantic producing moderate to locally fresh trade
winds across the region. Again, Thursday through Saturday appear
to contain the greatest potential for rainfall, possibly breaking
a recent dry spell.

&&

.AVIATION...Overall VFR conditions will continue across the
terminals, brief MVFR conditions with mtn obscurations are possible
due to passing shower activity across the eastern interior during
the early morning hours. Wind flow will be generally E with sea
breeze influences and hir gusts up to 28 kt. Afternoon convective
activity could also promote brief MVFR conditions at TJBQ 03/18-22Z.
Maximum winds NW 60-80 kts centered around FL380.
&&

.MARINE...A pulse of northeasterly swell is arriving this morning,
combining with wind wave energy to produce choppy, and at times
confused seas. A Small Craft Advisory remains in effect today for
the Offshore Atlantic Waters and the Anegada Passage, also for
the northern Coastal Waters of Puerto Rico during the afternoon
hours. Conditions will remain hazardous into the week as similar
conditions prevail.

For beachgoers, due to breaking wave around 10 feet today for the
northern coastline of Puerto Rico including Culebra, there is a High
Surf Advisory. A High Risk of Rip Currents is in effect for these
areas and also for the USVI and Vieques. Expect similar conditions
throughout the week.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through Tuesday afternoon for PRZ001-002-
005-008-012.

High Surf Advisory until 6 AM AST Tuesday for PRZ001-002-005-008-
012.

High Rip Current Risk through Tuesday afternoon for PRZ010.

High Rip Current Risk through this afternoon for PRZ013.

VI...High Rip Current Risk through Tuesday afternoon for VIZ001.

High Rip Current Risk through late tonight for VIZ002.

AM...Small Craft Advisory until 2 PM AST Tuesday for AMZ711.

Small Craft Advisory from 2 PM this afternoon to 8 PM AST this
evening for AMZ712.

Small Craft Advisory until 2 PM AST this afternoon for AMZ723.

&&

$$

SHORT TERM...WS
LONG TERM....RC

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
527 AM AST Tue Apr 4 2023

.SYNOPSIS...
Moderate to fresh easterly winds will continue across the local
area today along with an increase of moisture, beginning a wet
trend compared to the recent dry conditions. Weather conditions
will deteriorate tomorrow night due to an upper level cut-off low
interacting with a surface trough on Thursday. Thunderstorms and
flooding is possible into the weekend. Strong winds at times over
the regional waters will produce hazardous conditions.

&&

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

High pressure over the mid latitude Atlantic waters and low pressure
off the coast of Colombia will continue to drive moderate to fresh
easterly winds across the local area. Although the remnants of an
old front will edge toward the area today, a trough in the low to
mid levels will develop over the Leeward Islands later tonight and
move across the area on Thursday, followed by flow from the south
southeast at 700 mb. Precipitable water will increase significantly
today through Thursday as the trough moves through bringing better
shower chances, deeper moisture and hopefully sufficient rain to
begin the process of reversing the abnormally dry conditions.

A trough at upper levels will begin to dig south southeast into the
area later this afternoon and a jet of up to 70 knots will wrap
around the trough across and south of the southwest edge of Puerto
Rico and Saint Croix. On Wednesday the jet will sink south and a cut-
off low will drop into the area placing Puerto Rico and the U.S.
Virgin Islands on the divergent side of the low and further enhance
the unstable conditions. Since moisture is still not as abundant as
during summer months this will help bring better shower activity.
Temperatures will also be a few degrees cooler both at the surface
and aloft by Thursday as the GFS is still predicting between 12 to
13 degrees below zero at 500 mb.

&&

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

An upper level low continues to sit over the Eastern Caribbean with
it's divergence sector just south of Puerto Rico, causing unstable
weather to prevail into the weekend. Most rainfall will be seen
across the eastern half of the region, including the eastern half
of Puerto Rico and the USVI where there will be a chance of
flooding. Southeasterly surface wind flow will allow afternoon
convection to form across northwestern Puerto Rico during the
afternoon hours and streamers may form downwind of El Yunque or
the smaller islands. A similar pattern will continues until about
Monday when an area of low pressure builds in the western Atlantic
causing the surface windflow to become more southerly resulting
in an increase of showers across northern Puerto Rico during the
afternoon hours. Throughout this long term period, precipitable
water values remain over 1.5 inches, which is sufficient for
noticeable amounts of rainfall compared to the recent dry
conditions. Cloudy skies will prevail during this time.

&&

.AVIATION...While VFR conditions prevail at the moment, moisture is
increasing and will allow clouds and showers to form later this
morning aft 04/15Z in the east and spread to the west aft 04/17Z.
Areas of MVFR conditions and mtn obscurations are expected then.
Winds will increase to 12 to 18 knots with gusts to 26 knots psbl.
Winds will subside to less than 10 knot most areas by 05/00Z.
Maximum winds NW 40-55 kts btwn FL370-510.

&&

.MARINE... A lingering small northeasterly swell and wind swell
combine to produce seas around 5 feet today with occasionally
greater heights across the local waters. Winds will generally be
from the east around 15 to 20 knots with stronger gust. Tomorrow
conditions will deteriorate across the Offshore Atlantic waters
due to strong winds. Overall a similar trend will continue
throughout the next several days.

Today a High Rip Current Risk is in effect for the northern coast
of Puerto Rico and the northern USVI due to breaking waves up to 9
feet. Tonight, St. Croix will join. A trend of smaller waves is
forecast for the weekend and beyond due to a lack of swell.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through Wednesday afternoon for PRZ001-002-
005-008-012.

VI...High Rip Current Risk through Wednesday afternoon for VIZ001.

High Rip Current Risk from this evening through Wednesday
afternoon for VIZ002.

AM...Small Craft Advisory from 8 AM Wednesday to 8 AM AST Thursday
for AMZ711.

&&

$$

SHORT TERM...WS
LONG TERM....RC

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
527 AM AST Wed Apr 5 2023


.SYNOPSIS...
Weather conditions will begin to worsen today as a trough in the
upper levels begins to dig into the area. Thunderstorms and the
chance of flooding is expected during the next couple days. Breezy
conditions will continue as well, especially near shower
activity. Conditions will begin to improve on Sunday, however
moist, southeasterly flow will continue to promote rain. Marine
conditions remain choppy due to moderate to locally fresh winds.

&&

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

High pressure over the mid latitude Atlantic waters and low pressure
off the coast of Colombia will continue to drive moderate to fresh
easterly winds across the local area. Although the remnants of an
old front have settled just north of the area today as evidenced by
sporadic thunderstorms, a trough in the low to mid levels over the
Leeward Islands will move across the area on Thursday, followed by
flow from the south southeast at 700 mb. Precipitable water will
increase significantly today through Friday as the trough moves
through. Better moisture is already apparent in the GOES Total
Precipitable Water product with higher values both north and south
of Puerto Rico and the U.S. Virgin Islands.

A trough at upper levels has begun to dig south southeast into the
area and a jet of up to 70 knots is seen over Puerto Rico and Saint
Croix. The jet will sink south today and a cut-off low will drop
into the area on Thursday, placing Puerto Rico and the U.S. Virgin
Islands on the divergent side of the low and further enhancing the
unstable conditions. Some thunderstorms are likely to occur in the
forecast area today through Friday. Since moisture is still not as
abundant as during summer months this will help bring better shower
activity, but very high amounts of rainfall should be limited in
area--and likely will form over western Puerto Rico. Temperatures
will also be a few degrees cooler both at the surface and aloft
today and Thursday as the GFS is still predicting between 12 to 13
degrees below zero at 500 mb today though Thursday morning.


&&

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

A stationary upper level trough remains over the region on
Saturday, furthering a wet pattern of scattered to numerous
showers with isolated thunderstorms. A east-southeast wind flow
will cause most of the activity to occur across eastern Puerto
Rico and the USVI, followed by afternoon convection across
northwestern PR. The trough begins to depart to the east on
Sunday, causing an improvement in weather conditions as we enter
the week. However, precipitable water values remain between the
1.2-1.6 range which will maintain passing showers and afternoon
convection each day.

An area of low pressure begins to build east of Florida on
Tuesday, causing the surface winds to veer becoming south-
southeasterly. This will cause afternoon convection to form along
the northern sections of Puerto Rico preceded by greater maximum
temperature values. Moist air is associated with this flow,
continuing the pattern of passing showers across southern
sections throughout this time. This area of low pressure remains
far enough north to not have much of an impact on stability, yet
has a chance of increasing the amount of showers across the
regional waters.

&&

.AVIATION...While VFR conditions prevail at the moment, moisture is
increasing and will allow clouds and showers to increase in Ern PR
and along the nrn coast with lcl MVFR and mtn . SHRA/TSRA will
spread to the west aft 04/16Z. Areas of MVFR conditions and mtn
obscurations are expected then. ENE winds will increase to 12 to 20
knots with gusts to 30 knots psbl nr TSRA. Winds will subside to
less than 12 knot most areas by 05/00Z. Maximum winds WNW-NW 50-65
kts btwn FL3335-425.

&&

.MARINE... Moderate to locally fresh easterly winds continue to
produce choppy seas across the region waters. Seas are around 4
to 6 feet with occasionally greater heights. Weather conditions
will begin to deteriorate by tonight with increasing shower and
thunderstorm activity through the rest of the workweek. Wind gust
may become strong, nearing 30 knots, within showers. Small Craft
should exercise caution across most waters due to all of this and
a Small Craft Advisory will begin for the Offshore Atlantic
Waters, the Anegada Passage, and the Offshore Caribbean Waters
tomorrow for some time.

Surf heights remain up to 7 feet for the northern coastlines of
Puerto Rico and the USVI causing High Rip Current Risks to
continue. Conditions will improve into the week from the lack of
swell and weakening wind waves.


.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through late tonight for PRZ001-002-005-
008-012.

VI...High Rip Current Risk through late tonight for VIZ001.

High Rip Current Risk until 6 AM AST early this morning for
VIZ002.

AM...Small Craft Advisory from 8 AM to 8 PM AST Thursday for AMZ711.

Small Craft Advisory from 8 AM to 2 PM AST Thursday for AMZ723.

Small Craft Advisory from 2 PM to 8 PM AST Thursday for AMZ733.

&&

$$

SHORT TERM...WS
LONG TERM....RC

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
503 AM AST Thu Apr 6 2023


.SYNOPSIS...
Issued at 418 AM AST Thu Apr 6 2023

A cut-off low wobbling just northwest of the forecast area for the
next several days and the passage of a low level trough from the
east will support showers and thunderstorms for the next several
days. Southeast winds following the trough will bring a warming
trend to the north coast during the early part of next week, but
moisture patches will cause significant showers through mid-week.

&&

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

Unsettled weather conditions including numerous showers and isolated
thunderstorms will prevail today as an upper level cut-off low
strengthens just northwest of Puerto Rico. During the morning
hours, the eastern half of the region will see the bulk of
activity until around midday when convection driven by the passage
of a lower level trough from the east generates showers and
thunderstorms in the interior to western areas of Puerto Rico.
Storms capable of producing frequent lightning and small hail are
possible due to strong divergence aloft and quite low 500 MB
temperatures, currently around minus 13C. With this activity
there is a chance of flooding for urban areas, roads, and small
streams with even the chance for flash flooding to occur. Strong
thunderstorms will also be seen across the regional waters
throughout this time. After the trough passage today winds will
become more southeasterly at the surface and even southerly at
around 700 mb. This will cause the northwest to be the most
favored area for heavy rains during the afternoons and the
southeast coast during the night and early morning hours Friday
and Saturday.

As this upper level feature remains stationary over and northwest
of the area throughout the next couple days, organized convection
is forecast to continue as similar conditions prevail. Today and
tomorrow appear to be the most active, however unsettled weather
will linger into the weekend. During this time, high pressure at
the surface stretched across the northern Atlantic will continue
to promote moderate to locally fresh easterly winds across the
area, allowing showers to be frequent and quick moving.

&&

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

By Sunday the upper level trough begins to move toward the east.
This allows a shearline to approach the local area and prolongs fairly
deep southeasterly flow in the 1000-700 mb layer. Moisture becomes
patchy but the wet areas that pass will be significant and will
support good shower activity across the area. 500 mb temperatures
will still be around minus 10 degrees on Sunday and afternoon
thunderstorms will still be likely, but those temperatures will
warm to minus 7 degrees on Monday and possibly minus 6 degrees on
Tuesday which will greatly decrease the instability over the area.
This is expected to extinguish thunderstorm activity by Monday.

&&

.AVIATION...
(06Z TAFS)
Issued at 418 AM AST Thu Apr 6 2023

SHRA/TSRA are expected to continue during the next 24 hours
across the forecast area. This will cause periods of MVFR to
possible IFR conditions at times, particularly this morning in and
around the U.S. Virgin Islands and eastern Puerto Rico. BKN/OVC
cigs btw FL030-Fl070 and mtn tops obscd will likely persist
through the period. E-ENE winds around 15 kt with gusts to 35 kts
possible thru 07/10Z. Maximum winds WNW 60-70 kts btwn FL350-390
and W-WNW 60-75 kts btwn FL445-515.

&&

.MARINE...
Issued at 418 AM AST Thu Apr 6 2023

Except near thunderstorms and in the local outer Atlantic waters
today, seas are expected to remain below 7 feet in the forecast
area. Seas in the local outer Atlantic waters are also expected to
build to 7 feet Friday and Friday night and continue into
Saturday both due to increasing winds and a modest northerly
swell.

Rip currents will be moderate through Friday night except for the
most protected southern beaches.


&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...Small Craft Advisory until 8 PM AST this evening for AMZ711.

&&

$$

SHORT TERM/AVIATION...RC
PUBLIC...MMC
LONG TERM...WS

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
522 AM AST Fri Apr 7 2023


.SYNOPSIS...
Another day of active weather is expected as conditions remain
unstable. Showers and thunderstorms are forecast to continue for
the next few days. Moderate to locally fresh easterly winds will
continue across the area. Weather conditions will begin to improve
on Sunday, however a wetter pattern will continue into next week
as we transition out of the dry season. Strong winds over the
local waters will cause marine conditions to deteriorate
overnight into the weekend. There is a moderate risk of Rip
Currents for most beaches of PR and the USVI.


&&

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

A lower level trough is now moving west across the Dominican
Republic with southeast to south flow in tow behind it. An upper
level trough and cut-off low continues to spin above it today but
will begin to be absorbed on Saturday. The upper level trough will
cross Puerto Rico and the U.S. Virgin Islands on Sunday morning and
that will usher in northwest flow aloft and begin to increase the
stability over the area. 500 mb temperatures, however, will continue
to hold below minus ten degrees C during the period which will allow
widely scattered thunderstorms to form during the times of maximum
heating over land and over the local waters overnight. Moisture
levels will hold relatively steady during the period between 1.6 and
1.8 inches of columnar water, but after today, thunderstorms will
begin to become less frequent.

&&

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

Roughly 400 miles off of the southeastern seaboard an area of low
pressure migrates westward, becoming the dominant feature in the
the western half of the northern Atlantic. This will cause the
lower-level winds to veer, becoming southeasterly to south-
southeasterly by Monday morning. Warmer maximum temperatures are
expected on Monday and Tuesday for northern sections of Puerto
Rico, reaching in the 90s around noon. Also, afternoon convection
will form across the northern half of Puerto Rico on Monday. Lower
atmospheric moisture remains slightly above average during this
time, therefore showers capable of producing valuable rainfall are
in the forecast.

High pressure begins to build northwest of the region on Tuesday,
shoving the low pressure out into the Atlantic by midweek,
resulting in a backing of the winds to a more general easterly
flow by Wednesday. With this, afternoon convection will
concentrate in the interior to western sections of Puerto Rico.
Also, passing showers across wind exposed coastlines remain a
possibility at this time. Wednesday night into Thursday appears to
be a great time for rainfall as post frontal moisture from the
aforementioned low begins to advect over the region. Typical
windward shower activity with afternoon convection across the
Cordillera Central to western Puerto Rico will prevail.

&&

.AVIATION...VFR conds will prevail early, but SHRA/TSRA are expected
to redevelop aft 07/13Z across the FA. This will cause periods of
MVFR/IFR conds at times, particularly aft 07/16Z in NW Puerto Rico.
BKN/OVC cigs btw FL030-FL070 and mtn top obscurations will likely
persist through the period. E-ENE winds around 15 kt with stronger
gusts possible thru today. Maximum winds W-WNW 40-50 kts btwn FL430-
490.

&&

.MARINE... High pressure in the north Atlantic basin will continue
to drive easterly winds around 15 to 20 knots causing choppy seas
throughout the weekend. The dominant period is ranging from 6 to
8 seconds for today, before raising to around 9 second tomorrow as
winds strengthen across the outer waters. Wave heights are
reaching up to around 5 to 7 feet by tonight for the Offshore
Atlantic waters and the Anegada Passage, and will be lower
elsewhere. For this reason a Small Craft Advisory will be in
effect for the mentioned zones tonight through Sunday morning.
Small craft operators should still exercise caution across other
zones as winds as strong winds are possible from time to time.

Due to the lack of swell and weak wind wave energy, there is a
moderate risk of rip currents for the local islands as breaking
wave heights are forecast to be 5 foot or smaller. Northern and
eastern exposed coastlines will experience the most wave action
meanwhile southern and western Puerto Rico will have more tranquil
beach conditions.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...Small Craft Advisory from 8 PM this evening to 8 AM AST Sunday
for AMZ711-723.

&&

$$

SHORT TERM...WS
LONG TERM...RC

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
504 AM AST Sat Apr 8 2023

.SYNOPSIS...Unsettle weather Tomorrow, another round of afternoon
convection is expected due to the unstable conditions. Building
seas are expected for tonight, reaching 7 ft across the Atlantic
waters and the Anegada Passage.

&&

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

Low-level southeasterly trades and a mid-to upper-level low over
Hispaniola, in combination with deep moisture over the region
produced a lingering band of showers and thunderstorms across the
eastern half and southern portions of Puerto Rico. As of 4 AM,
observed rainfall amounts after midnight across southeastern Puerto
Rico were around 4 inches, and rivers in San Lorenzo and Juncos went
above flood stage. Meanwhile, strong thunderstorms with gusty winds
up to 40 mph were noted earlier across coastal areas of Yabucoa and
southwestern Puerto Rico.

At least for today, active weather is possible through the morning
hours across much of Puerto Rico as the mid-level low over
Hispaniola slowly weakens during the next 24 hours. Unstable
conditions should last through the weekend, with 500 mb temperatures
slowly increasing from -11C to -9C by Sunday afternoon. PWAT should
fluctuate between 1.50-1.75 inches, peaking today, and slowly
improving as a drier air mass with suspended Saharan dust continues
to filter over the area. Weather condition should further improve on
Monday, but diurnally induced afternoon showers should develop along
the Cordillera Central and northern PR due to south-southwesterly
steering winds.

&&

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

The most recent model guidance suggests a wet weather pattern
during the long-term forecast period, with precipitable water
values fluctuating between 1.50 and 1.75 inches, which is normal
to above-normal for this season. This trend may also suggests the
beginning of the transition into the local wet season,
characterized by increased shower activity led by local effects
and diurnal heating and a potential relief to current drought and
fire weather conditions. The expected shower activity will follow
the typical seasonal pattern, with the highest impact over the
interior to western sections following the general steering flow.
East-southeasterly winds at 10-15 mph gradually backing to the
east from Wednesday onwards means that the afternoon shower
activity will migrate from the northwestern quadrant on Tuesday
southward to the more western sections by the latter part of the
workweek. Southeasterly winds also suggest the potential for
excessive heat risks, particularly for portions of northern Puerto
Rico, where heat indices around 102 degrees are likely on
Tuesday.

&&

.AVIATION...Tempo MVFR to brief IFR conditions possible at
TJSJ/TJPS/TJBQ today. Expect mtn top obscd and periods of SHRA/TSRA
at least thru 22z. A gradual improvement is expected during the
night. Across the USVI terminals, mainly VFR conditions expected
through the period. HZ expected to filter through the day due to
Saharan dust.

&&

.MARINE...Moderate to locally fresh northeast winds up to 20
knots, gusting up to 30 knots, will maintain hazardous marine
conditions across the offshore Atlantic waters, where a Small Craft
Advisories remains in effect. Elsewhere, small craft operators
should continue to exercise caution due to wind-driven choppy
conditions.

For beachgoers, life-threatening rip currents are likely, and
thus, a high risk of rip currents, for the easternmost beaches of
Saint Croix. Elsewhere, excluding the beaches across the southern
and western coast of Puerto Rico, a moderate risk of rip currents
will continue, making life-threatening rip currents possible.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...High Rip Current Risk through late tonight for VIZ002.

AM...Small Craft Advisory until 8 AM AST Sunday for AMZ711-723.

&&

$$

SHORT TERM...DSR
LONG TERM....ICP
AVIATION...DSR
PUBLIC...ICP

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Sun Apr 9 2023

.SYNOPSIS...Suficient available moisture, marginal conditions
aloft, and local effects will support afternoon showers with
isolated thunderstorm development each day, mainly across western
sections. The resulting rains may promote limited to elevated
excessive rainfall hazard risks. Elsewhere, fair weather
conditions with limited shower activity will persist. Moderate
winds will maintain choppy marine conditions for small craft.

&&

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

The area will remains under the influence of a weakening mid-to
upper-level trough, which is still promoting 500 MB colder than
normal temperatures. Last night TJSJ sounding indicated -13
degrees Celsius. In terms of moisture, although there is some low
to mid- level drier air with Saharan dust over the region, the
precipitable water (PWAT) content is expected to range between
1.30-1.50 inches across the islands, with the max PWAT over
western PR. Therefore, the combination of the available moisture
with the sea breeze convergence, daytime heating and other local
effects will lead to the development of afternoon showers with
isolated thunderstorms over the northwestern quadrant of Puerto
Rico. Across the rest of the islands, streamer-type of showers
could develop with lesser amounts over the USVI, compared to
eastern PR.

On Monday and Tuesday, more stable condtions aloft are expected as
the upper level trough moves east of the forecast area. However,
PWAT will increase slightly due to the absence of the weak SAL
event. Therefore, weather conditions will be mostly driven by local
effects, and afternoon showers with possible isolated thunderstorm
can be expected each day over PR. Across the USVI, fair weather
conditions should prevail. Southerly wind flow should promote heat
indices in the mid to upper 90s across coastal areas of PR, and in
the low 90s across the USVI on both days.

&&

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

Model guidance continues to suggest wetter conditions through the
latter part of the workweek, but now with some drying by the end
of the weekend. Easterly perturbations in the general wind flow on
Wednesday and Thursday, followed by the remnants of a frontal
boundary from Friday onwards, will maintain total precipitable
water values should remain within normal to briefly above-normal
seasonal levels, ranging between 1.4 and 1.7 inches. Conditions
aloft will remain marginal for deep convective development
throughout the period, with the influence of a mid-to-upper trough
and subtropical jet. Although overnight and early morning showers
will still affect windward areas, the expected shower pattern will
be dominated by afternoon showers and possible isolated
thunderstorm development following local effects and the general
steering flow. East-southeasterly winds at 10-15 mph gradually
backing from the east on Thursday and from the east-northeast from
Friday onwards suggest that the afternoon shower activity cluster
will migrate southward from the northwestern to the southwestern
quadrant by the end of the workweek into the weekend. The
resulting rainfall accumulations may lead to flooding or excessive
rainfall hazard risks.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, SHRA/TSRA expected to
develop in and around TJBQ btw 17z-23z, which may cause tempo MVFR
to brief IFR conditions. At TJSJ, SHRA developing from the el Yunque
streamer may cause tempo MVFR conds in the afternoon hours. Sfc
winds E-ESE at 10-15 kt with sea breeze variations and gusts in the
mid 20s aft 14z. HZ due to Saharan dust will gradually improve
through the end of the forecast period.

&&

.MARINE...Marine conditions have improved. However, moderate east
to southeasterly winds up to 15 knots, gusting up to 25 knots,
will maintain choppy marine conditions, particularly across the
offshore Atlantic waters and the Anegada Passage, where seas up to
6 feet are likely. Elsewhere, mariners can expect seas of 5 feet
or below.

Except for western and southern beaches, a moderate risk of rip
currents remains in places for most local beaches, meaning that
life-threatening rip currents are possible.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

SHORT TERM...DS
LONG TERM....ICP
AVIATION...DS
PUBLIC...ICP

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
430 AM AST Mon Apr 10 2023

.SYNOPSIS...Seasonal moisture levels and local effects will
support afternoon showers with isolated thunderstorm development
each day, mainly across western sections of the islands. The
resulting rains may promote limited to elevated excessive rainfall
hazard levels or flooding impacts. Elsewhere, fair weather
conditions with limited shower activity will persist. From Tuesday
onwards, a northerly swell will gradually generate choppy to
hazardous and life-threatening surf zone conditions. Increased
shower activity is likely by Friday into the upcoming weekend.

&&

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

An elongated area of low pressure near Bermuda and an associated
front at the surface across the western Atlantic will continue to
move eastward and remain well north of the local area. In response,
the Azores High weakens, and a light south-to-southeasterly steering
wind flow sets up over the region through at least Tuesday. At the
mid and upper levels, a zonal flow with 50 kt westerlies will
prevail through the short-term period as a strong jet moves between
22N-30N, and the upper-level trough to our northeast loses its
influence over the area. As a result, a decreasing trend in the 500
MB temperatures of about a degree C is expected each day, from near
-7C today to -5C on Wednesday. However, this is still at seasonal
levels, and isolated thunderstorms could develop each afternoon
through at least Tuesday over portions of central and northern
Puerto Rico. On Wednesday, light to moderate easterly trades return
as a high pressure sets over the southwestern Atlantic. Regarding
moisture content, normal to above-normal precipitable water values
are expected, with a peak today of 1.70 inches, remaining at around
1.50 in. through the rest of the period. This will favor mainly
shower activity over Puerto Rico, while the U.S. Virgin Islands will
see lesser amounts in general. Urban and small stream flooding is
possible with the afternoon activity in PR.

&&

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

Model guidance continues to suggest wetter conditions, but now
with a gradual increase in moisture to around 1.8 inches and
above-normal levels between Friday and Monday with the arrival of
the remnants of an old frontal boundary from the east-northeast.
Conditions aloft will remain marginal for deep convective
development throughout the period, with the influence of a mid-to-
upper trough and subtropical jet.

Overnight and early morning trade wind showers moving inland from
the local waters will affect eastern Puerto Rico and the local
islands each day. Although the highest rainfall will result from
afternoon showers and possible isolated thunderstorm development
on Thursday and Friday, rains from showers moving inland from the
waters at nighttime and afternoon convective development over land
areas at daytime from Friday night onwards could be significant
enough to potentially relieve current drought and fire weather
conditions in some areas. These rains may also lead to flooding or
excessive rainfall hazard risks.

East winds at 10-15 mph gradually backing from the east-
northeast from Friday onwards as high pressure over the western
Atlantic migrates eastward into the north central Atlantic,
suggests that the afternoon (overnight) rains cluster will migrate
southward (northward) from western (eastern) sections to the
southwestern (northeastern) quadrant into the weekend. Winds will
slowly become more easterly and weaken by Monday.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, SHRA/TSRA expected to
develop near TJBQ/TJSJ btw 10/16z-23z, which may cause tempo MVFR
conditions and mostly VCTS. Sfc winds ESE at 8-14 kt with sea breeze
variations and occasional higher gusts at times aft 10/14z.

&&

.MARINE...Marine conditions will continue to improve, and mariners
can expect seas up to 5 feet and winds up to 15 knots. However, a
small northerly swell will likely generate choppy to hazardous
marine conditions by Tuesday night into Wednesday, requiring Small
Craft Advisories for portions of the local waters.

A moderate risk of rip currents remains in places for most beaches
of northern Puerto Rico and the easternmost shores of Culebra,
Vieques, and Saint Croix, meaning that life-threatening rip
currents are possible. The risk will elevate to high by Tuesday
into Wednesday for some of these beaches. In addition, there is a
potential for High Surf Advisory conditions across most north-
facing beaches by midweek. Stay tuned!

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk from Tuesday morning through Wednesday
afternoon for PRZ001-005.

VI...None.
AM...None.
&&

$$

SHORT TERM...DS
LONG TERM....ICP
AVIATION...DS
PUBLIC...ICP

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Tue Apr 11 2023

.SYNOPSIS...Rains from afternoon showers and isolated thunderstorm
development may promote limited excessive rainfall hazard levels
or flooding impacts, mainly across the interior, northern, and
western sections of Puerto Rico. The remnants of an old frontal
boundary may enhance showers' frequency and coverage during the
weekend. A northerly swell will gradually generate choppy marine
and life-threatening surf zone conditions from tonight onwards.

&&

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

An elongated area of low pressure east of Bermuda will continue to
move further into the north-central Atlantic today, and the Azores
High will further lose its influence over the local area. This
synoptic pattern will continue to promote a light southerly steering
wind flow across the local area. A front associated to the low
pressure area should remain north of the region through the short
term period. However, moisture associated to the front could advect
across the local Atlantic waters by Thursday night. Meanwhile, the
region will remain between a strong jet over the Atlantic waters and
the subequatorial ridge over the Caribbean Sea. This should provide
more stable conditions aloft, and could inhibit thunderstorm
development later in the period.

Regardless, locally induced afternoon showers with possible isolated
thunderstorms are expected to develop today over the interior of PR,
while slowly drifting erratically through the evening hours over
land areas due to the light steering winds. On Wednesday, trade
winds start to pick up and afternoon convection should develop
mainly over the western interior and northwest PR. Then on Thursday,
as trades shift from the northeast in response to the building high
behind the front, expect an advective pattern to favor showers at
times across the USVI and east/northern PR during the
morning/evening hours, and the focus of afternoon shallow convection
will shift over the southwestern quadrant of PR.

&&

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

A relatively wetter pattern should persist through the weekend,
followed by drier conditions early next week. So far, the highest
precipitable water values of around 1.7-1.8 inches and above-
normal levels are likely between Saturday morning and Sunday afternoon,
caused by the remnants of an old frontal boundary moving in from
the east-northeast. Conditions aloft will remain marginal for deep
convective development, with mid-to-upper troughs and the
associated subtropical jet maintaining a weak trade wind cap
inversion and 500 mbar temperatures around -6 to -7 degrees
Celsius.

Even during the driest periods, afternoon convective development
is expected, following the general steering flow. However, showers
moving inland from the local waters could generate substantial
rainfall accumulations, particularly during the weekend. While
the expected rains may present the potential for limited excessive
rainfall hazard risk or flooding impacts, they can also relieve
some areas' current drought and fire weather conditions.

East-northeast winds at 10-20 mph gradually veering from the east-
southeast and weakening to 10-15 mph as the dominant surface high
pressure moves further eastward into the North Atlantic. This
pattern suggests that the afternoon (overnight) rains cluster will
migrate northward (southward) from the southwestern (northeastern)
sections to the northwestern (southeastern) quadrant.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, SHRA/TSRA expected to
develop over central PR, which may cause VCTS and brief MVFR cigs at
the PR terminals btw 11/16z-23z. Sfc winds ESE at 8-12 kt with sea
breeze variations and occasional higher gusts at times aft 11/14z.

&&

.MARINE...Mariners can expect seas up to 5 feet and winds up to 15
knots today. However, a small northerly swell will likely
generate choppy marine conditions from tonight onwards, meaning
that small craft operators should exercise caution.

Life-threatening rip currents are likely across the surf zone from
Arecibo eastward to Carolina across the north coast of Puerto
Rico, where a high risk of rip currents is in place. A moderate
risk of rip currents remains in place for the remaining north-
facing beaches of Puerto Rico, Culebra, Vieques, and Saint Croix,
meaning that life-threatening rip currents are possible. However,
the risk will elevate to high for the beaches of northwestern and
northeastern Puerto Rico and Culebra tonight and for beaches of
Aguada and Rincon across the western coast of Puerto Rico and the
northern U.S. Virgin Islands by Wednesday morning.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk from 6 AM AST this morning through
Wednesday afternoon for PRZ001-005.

High Rip Current Risk from this evening through Wednesday
afternoon for PRZ002-008-012.

High Rip Current Risk from Wednesday morning through Wednesday
afternoon for PRZ010.

VI...High Rip Current Risk from Wednesday morning through Wednesday
afternoon for VIZ001.

AM...None.
&&

$$

SHORT TERM...DSR
LONG TERM....ICP
AVIATION...DSR
PUBLIC...ICP

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
507 AM AST Wed Apr 12 2023

.SYNOPSIS...Afternoon showers with isolated thunderstorm
development are likely to produce limited flooding impacts, mainly
across the interior and western to northwestern sections of Puerto
Rico. The remnants of an old frontal boundary may enhance shower
activity during the weekend, increasing the potential for flooding
impacts. A northerly swell will maintain choppy marine and life-
threatening surf zone conditions through at least Thursday.

&&

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

A mid-level ridge over the Caribbean Basin will continue to promote
dry air intrusion and warming of the 500 MB temperatures through the
short term period. A 50-60 kt upper-level jet stream will move near
the islands today, this may aid in the development of brief isolated
thunderstorms over western PR during the afternoon hours. Trade
winds are expected to increase somewhat today and turn more from the
east. Then on Thursday and Friday, winds turn more east to northeast
as a high pressure builds behind a cold front over the western
Atlantic. This will promote colder air moving over warmer waters,
and an advective pattern with showers increasing in and around the
northern and eastern sections of PR and the USVI is expected during
the nighttime/early morning hours. Meanwhile, across southwestern
PR, afternoon shower development due to daytime heating and other
local effects is expected each day. Ponding of water in roads and
poor drainage areas can be expected with the afternoon shower
activity over western PR through the short-term period.

&&

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

Marginally unstable conditions aloft, with a weak trade wind cap
inversion and seasonal mid-level temperatures around -6 to -7
degrees Celsius, and increased moisture levels around 1.7-1.8
inches enhanced by the remnants of an old frontal boundary, should
lead to yet another wet weekend with enhanced shower and possible
isolated thunderstorm development. Most land areas should observe
measurable rains. However, the highest impact is likely across
portions of eastern and interior to western sections of Puerto
Rico, where limited to elevated flooding impacts are possible.
Model guidance has remained relatively persistent with this wet
pattern, but there are still some uncertainties regarding the
timing of the highest moisture and limitations due to increased
cloud coverage.

Variable weather conditions are likely early next week, influenced
by intermittent patches of relatively dry and moist air streaming
across the region. Afternoon showers and possible isolated
thunderstorm activity clustering along the interior to western
sections of Puerto Rico following the general steering flow and
reinforced by local effects and diurnal heating is likely each
day. Despite significant variations in moisture levels and limited
areal coverage, the resulting rains may lead to localized
flooding impacts.

East to east-northeast winds at 10-20 mph will prevail. Still, as
the dominant surface high pressure to our north continues to move
eastward into the north-central Atlantic, brief variations in the
general wind flow are possible. The overall wind pattern,
including prevailing east-northeast to northeast winds at the
850-700 mbar layer, suggests that afternoon (overnight) rains will
favor the interior and western to southwestern (eastern to
northeastern) sections.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, afternoon SHRA/TSRA
expected to develop over western PR, which may cause VCTS at TJBQ.
Across TJSJ/TJPS, mostly VCSH due to locally induced SHRA btw 12/16z-
21z. Sfc winds ESE at 10-15 kt with sea breeze variations and
occasional higher gusts aft 12/14z.

&&

.MARINE...A small northerly swell will maintain choppy marine
conditions, with seas up to 6 feet, mainly across the Atlantic
waters, where small craft operators should exercise caution.
Elsewhere, marines can expect seas of 5 feet or below and easterly
winds up to 15 knots.

Life-threatening rip currents are likely across the surf zone from
Rincon eastward to Fajardo across northern Puerto Rico, Culebra,
and Saint Thomas, where a high risk of rip currents is in place. A
moderate risk of rip currents remains in place for the beaches of
southwestern Puerto Rico, Vieques, and Saint Croix, meaning that
life-threatening rip currents are possible.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through late Thursday night for PRZ001-005-
008.

High Rip Current Risk through late tonight for PRZ002-010-012.

VI...High Rip Current Risk through late tonight for VIZ001.

AM...None.
&&

$$

SHORT TERM...DSR
LONG TERM....ICP
AVIATION...DSR
PUBLIC...ICP

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
331 AM AST Thu Apr 13 2023


.SYNOPSIS...
Afternoon showers are expected to continue across western and the
interior of Puerto Rico for each day. At least ponding of water on
roadways is expected with the activity. A weak frontal boundary
will bring an increase in showers for the weekend. A small
northerly swell will cause seas 4 to 6 feet through today.

&&

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

The Doppler radar only showed a few showers moving across the local
waters without affecting any landmass during the overnight hours. A
dry air mass will continue to prevail over the local forecast area
as a mid level ridge dictates the weather conditions across the
local region through at least this afternoon. Between this afternoon
and Saturday, winds are forecast to turn more east to northeast as a
high pressure builds behind a cold front over the western Atlantic.
Due to the change on the wind pattern later on today and increasing
moisture associated to the cold front, this will increase the
chances of showers along the north coast of Puerto Rico and the
northern U.S. Virgin Islands during the overnight hours. Meanwhile,
across southwestern PR, afternoon shower development due to daytime
heating and other local effects is expected each day. Ponding of
water in roads and poor drainage areas can be expected with the
afternoon shower activity over western PR through the short-term
period.


&&

.LONG TERM...Sunday through Thursday...
The remnants of a frontal boundary will continue to push into the
islands on Sunday, increasing the moisture content at the surface
and into the mid-levels. Conditions aloft will also be marginally
unstable as a piece of the jet stream crosses the northeastern
Caribbean. As a result, showers will continue to move in across
eastern Puerto Rico and the U.S. Virgin Islands, while stronger
activity should develop in the afternoon for the interior and west
of Puerto Rico. Ponding of water on roadways and isolated urban
ans small streams can be expected with this activity. Conditions
could favor the development of some isolated thunderstorms as
well, although mid-level temperatures are expected to be near
normal.

For the first half of the next workweek, columnar moisture will
decrease, but just a little. A high pressure migrating into the
central Atlantic will maintain out of the east to east-northeast
at around 10 knots. Irregular patches of moisture will move in at
times, resulting in-once again-showers being advected into eastern
Puerto Rico and over the U.S. Virgin Islands, with afternoon
convection firing up across the interior and west each afternoon.
At the mid-levels, a ridge will maintain a dry air mass, so
convection should remain below these levels. Regardless, any area
that receives heavy rain could experience ponding of water on
roadways and low-lying areas.

&&

.AVIATION..Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, afternoon SHRA expected
to develop over western PR. Across TJSJ/TJPS, mostly VCSH due to
locally induced SHRA btw 13/16z-21z. Sfc winds ESE at 10-15 kt with
sea breeze variations and occasional higher gusts aft 13/14z.


&&

.MARINE...
The most recent observations from the buoy network show seas of 3
to 5 feet, and a period of 5 seconds across the Atlantic. A small
northerly swell will continue to impact the local waters through
tomorrow. Small craft operators are urged to exercise caution due
to expected seas up to 6 feet. There is a high rip current risk in
effect for northern Puerto Rico.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through late tonight for PRZ001-005-008.

High Rip Current Risk until 6 AM AST early this morning for
PRZ002-012.

VI...High Rip Current Risk until 6 AM AST early this morning for
VIZ001.

AM...None.
&&

$$

SHORT TERM...EM
LONG TERM....ERG

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
455 AM AST Fri Apr 14 2023

.SYNOPSIS...
cloudy skies with passing showers will persist during the morning,
with the typical induce weather pattern in the afternoon.
Deteriorate weather conditions are forecast for the night as
remnants of a frontal boundary sink southward reaching the
islands increasing the frequency of passing showers. A showery
pattern is forecast to remain for the next several days, due to
the remnants of the frontal boundary.

&&

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

A mixture of sunshine and clouds will prevail this morning, with a
few trade wind showers arriving across the windward sections of
Puerto Rico and the U.S. Virgin Islands. A mid to upper-level ridge
will promote subsidence aloft, limiting vertical development today.
However, locally induced convection will result in scattered to
locally numerous showers across the interior or western sections of
Puerto Rico, especially during the afternoon and early evening. We
do not rule out ponding of water in poorly drained areas with the
heaviest activity.

Although the ridge will persist aloft on Saturday, the moisture
associated with the remnants of a frontal boundary will be pushed
over the islands by the east-northeast winds, promoting cloudy and
showery weather. Rain activity will be enhanced by surface
convection, sea breeze variations, local effects, and diurnal
heating, especially during the afternoon. Urban and small stream
flooding may be possible across northeast and western Puerto Rico.
The lingering moisture associated with the front may continue to
result in showery weather through Sunday. If the frontal boundary
sink over the islands, we may expect near-to-below-normal minimum
temperatures during the weekend.


&&

.LONG TERM...Monday through Friday...
A surface high pressure over the Central Atlantic will dominate
the first part of the long term. This surface feature will
maintain well above low-level moisture across the area, dragging
patches of the remnants of the previous frontal boundary. As a
result, expect frequent arrivals of cloudiness and passing
showers. Given the easterly component in winds, the focus of the
showers on Monday through Wednesday will be in the windward
sections in the morning and evening and across the western
interior with the local effects and the diurnal heating.

Late Wednesday into Thursday, the surface ridge will move more
eastward, pushed by another frontal boundary moving southward.
Although winds are forecast to remain from the east, some
northerly component could be present due to a pre-frontal trough
just over the north of the Hispaniola, just before the front
dissipates. In this evolving pattern, PWat values near 1.5 to 1.6
inches will persist, increasing the potential for shower
development. On Thursday, jet maxima are forecast to be over the
area. This will induce colder temperatures at 500 at around -8
Celsius, which will drive isolated thunderstorms, as suggest the
Galvez- Davison Index (GDI), which shows the best potential in
the afternoon over the western sections of Puerto Rico.

For Friday, model guidance indicates a relaxation in the pressure
gradient and veer winds, responding to a deep upper-level trough
reflected in all the levels. The mid to upper-level feature will
induce instability aloft, resulting in colder temperatures at
500MB. Since forecast confidence is still low, please stay tuned
for changes that may be included in the forecast as we get
closer.

&&

.AVIATION...
VFR conditions will prevail across the local flying area today, with
the arrival of a few quick passing showers at times. Cloudiness and
SHRA/+SHRA may develop across the Cordillera Central between 14/17-
23z, affecting JBQ or JPS, especially in the vicinity. Winds will
remain calm-light/VRB through 14/13z when they return from the E to
ENE at around 15 kt with higher gusts and sea breeze variations.

&&

.MARINE...
Surface high pressure over the Central Atlantic will continue to
result in a moderate easterly wind pattern across the region.
Therefore, expect winds up to 15 knots for most of the waters,
with some gusty winds across the offshore and unprotected waters.
A small northerly swell is diminishing across the local waters.
However, it will continue to result in long periods, affecting the
breaking waves across the north coast of Puerto Rico. Therefore, a
high risk of rip current for the north-exposed beaches from
Aguadilla to Fajardo and the north-exposed beaches of Culebra
through this afternoon. The risk will remain moderate to low for
the rest of the beaches.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through this afternoon for PRZ001-005-008.

High Rip Current Risk through this afternoon for PRZ002-012.

VI...None.
AM...None.
&&

$$

SHORT TERM & AVIATION...CAM
LONG TERM & MARINE....LIS

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
454 AM AST Sat Apr 15 2023

.SYNOPSIS...
Issued at 449 AM AST Sat Apr 15 2023

The remnants of a frontal boundary will increase moisture and
shower activity today. However, a ridge pattern aloft will limit
the vertical development and intensity. An advective pattern will
prevail Sunday onward, pushing a few showers across the Virgin
Islands and the windward sections of Puerto Rico. Locally induced
convection will develop each afternoon across PR's interior and
western sections and downwind from the USVI. A short wave trough
will swing by the region by the second part of the upcoming
workweek, which may increase instability.

&&

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

A showery pattern is forecast for today, with an increase in the
frequency of the passing showers as a stationary frontal boundary
just north of the islands will continue to provide remnants of
moisture, with PWAT values reaching nearly 1.7 inches. This
pattern will persist during the day as the front dissipates and
merge between Hispaniola and Puerto Rico. The heaviest activity is
not anticipated during the morning hours. However, some localized
downpours cannot be ruled out. In the afternoon, the local
effects and the available moisture will result in a round of
showers across the western interior sections. Although moderate to
heavy rains are anticipated, conditions at the upper level are
not favorable for thunderstorms; however, persistent showers can
result in one isolated thunderstorm.

According to the model guidelines, the bulk of low-level moisture
from the frontal boundary will be between late Saturday into
Sunday. A better upper-level dynamic will be present as a jet
moves over the area, increasing the divergence aloft. These
conditions mentioned above would increase the potential for
vertical development. Therefore, the forecast calls for an active
afternoon over the western sections, followed by clusters of
showers across the windward sections of the islands and north
Puerto Rico.

On Monday, conditions will improve as a patch of drier airmass
filters into the islands embedded in the east-northeasterly winds.
This lack of moisture, the stable conditions aloft, and a mid-
level ridge will drive mostly clear to partly cloudy skies with
the typical afternoon showers resulting from the local effects and
diurnal heating. Nevertheless, as of today, Monday looks like the
driest day.

&&

.LONG TERM...Tuesday through Sunday...

A surface high pressure across the Atlantic Water will promote an
east-to-east-southeast wind flow across the islands Tuesday
through early Thursday. These winds will advect fragments of
moisture each day across the islands, resulting in occasional
showers across the windward sections in Puerto Rico and the U.S.
Virgin Islands. At the same time, a mid to upper-level ridge will
create hostile environmental conditions for the vertical
development and intensification of these showers.

Model guidance suggests a short wave trough approaching from the
west and weakening the ridge pattern aloft, which may undermine
the trade wind cap, allowing vertical mixing above 700 MB. This
scenario could increase instability, promoting better-organized
convection, especially on Thursday afternoon and evening and
possibly around Friday afternoons. The GFS Galvez-Davison Index
(GDI) also indicates the potential for scattered to numerous
convective activity. We also include isolated thunderstorms in the
forecast. The mid to upper-level trough may be amplified (even
more) by next weekend, increasing instability. The limiting factor
for organized convection would be the available moisture.

&&

.AVIATION...
(06Z TAFS)
Issued at 449 AM AST Sat Apr 15 2023

VFR conditions will prevail for all the TAF sites during the
period. Brief periods of showers can result in some reduction in
VIS; however, no significant impacts are expected. Winds will
remain from the E at 5 knots with gusty winds near the showers,
increasing to 12 knots from the E with sea breeze variation at
15/15Z. VCSH will persist for TJSJ, TIST & TISX between 15/06Z to
15/18Z, increasing them across TJBQ.

&&

.MARINE...
Issued at 449 AM AST Sat Apr 15 2023

Winds will intensify later today, and winds speed between 15 and
20 knots are likely across the Atlantic and Caribbean Passages by
this afternoon and evening. In addition, a small northeasterly
swell will move across the local waters. Therefore, today and
tomorrow, expect confused choppy seas between 4 and 6 feet across
the local waters. Seas will slowly improve early next week. A
northeasterly swell may arrive by mid-week (around Wednesday).

Please exercise caution across the surf zone along the exposed
Atlantic beaches due to possible rip current formation.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

SHORT TERM, AVIATION...LIS
SYNOPSIS, LONG TERM, MARINE....CAM

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
441 AM AST Sun Apr 16 2023


.SYNOPSIS...
Issued at 425 AM AST Sun Apr 16 2023

The easterly winds will push another fragment of moisture,
resulting in passing clouds and showers across the local waters,
the Virgin Islands, and the windward sections in Puerto Rico.
Local effects and sea breeze will promote afternoon convection
across the interior and western PR. However, a ridge aloft will
hinder the formation of thunderstorms. The advective pattern will
continue through mid-week, with locally induced convection each
afternoon across PR's interior and western sections and downwind
from the USVI. A mid to upper-level trough will amplify over the
northeast Caribbean throughout the second part of the week, which
may increase instability.

&&

.SHORT TERM...Tonight through Tuesday...

A variable weather pattern will persist for the day as remnants
of a frontal boundary located just north of the islands converge
over the islands. GOES-E derived PWAT values indicated between 1.5
and 1.6 inches across the islands. This increase in low-level
moisture will maintain frequent light to moderate passing showers
across the northeastern sections of Puerto Rico and the local
waters. As the day progresses, frequent passing showers will
persist over the northeastern sections of Puerto Rico and St.
Thomas. Given the northeasterly winds, the afternoon showers will
focus on the southwestern quadrant PR.

According to the model guidance, low-level moisture is forecast
to diminish across the islands as a patch of dry air filters into
the area Monday and Tuesday. Although weather conditions would
remain mostly stable, afternoon convection is still expected
across the interior sections due to the diurnal, sea breeze and
local effects. Daytime temperatures are forecast to reach the mid
80s across the coastal areas and the mid to upper 70s across the
mountains.

&&

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

A surface high pressure across the Atlantic Water will keep a
cold front away, off to the northwest of the islands. The surface
high will promote an easterly wind flow across the islands through
early Thursday. However, a trade wind perturbation may pool
moisture over the region, creating a showery pattern from early
Wednesday to early Thursday morning. At the same time, a short
wave trough accompanying an upper-level jet will swing by the
region on Thursday, increasing instability. Even more, model
guidance suggests weakening the ridge aloft, which may undermine
the trade wind cap, allowing vertical mixing above 700 MB through
the second half of the week.

The GFS Galvez-Davison Index (GDI) indicates an unstable weather
pattern with the potential for scattered to numerous convective
activity, especially Friday through the weekend. Therefore, we
have isolated thunderstorms in the forecast from Thursday through
Sunday. The mid to upper-level trough may be amplified (even more)
by next weekend, increasing instability. The limiting factor for
organized convection would be the available moisture and the
trough's final position concerning the islands.


&&

.AVIATION...
(06Z TAFS)
Issued at 425 AM AST Sun Apr 16 2023

VFR conditions will prevail for all the TAF sites during the
period. Brief periods of showers can result in some reduction in
VIS; however, no significant impacts are expected. Winds will
remain from the NE at 5 knots with gusty winds near the showers,
increasing to 12 knots from the E-NE with sea breeze variation
at/after 16/14Z. VCSH will persist for TJSJ, TIST & TISX through
16/15Z, increasing them across TJPS after 16/18Z.

&&

.MARINE...
Issued at 425 AM AST Sun Apr 16 2023

Easterly winds between 15 and 20 knots will maintain choppy seas
between 3 and 6 feet across the Atlantic and Caribbean Passages
today. Seas will slowly improve early next week. However, a
northeasterly swell may arrive by mid-week (around Wednesday)
without significant impact on small crafts (at this time).

Please exercise caution across the surf zone along the exposed
Atlantic beaches of Puerto Rico, including Culebra and the north
and east coast in St Croix, due to possible rip current
formation.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

SHORT TERM, AVIATION...LIS
SYNOPSIS, LONG TERM, MARINE....CAM

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
353 AM AST Mon Apr 17 2023

.SYNOPSIS...
Issued at 347 AM AST Mon Apr 17 2023

The U.S. Virgin Islands and Puerto Rico can expect a mixture of
sunshine and clouds through the morning hours, followed by
convective activity across the interior and southwestern sections
of Puerto Rico during the afternoon. The advective pattern will
last through mid-week. The ridge aloft will weaken Thursday onward
as a mid to upper-level trough amplify over the Northeast
Caribbean, which may increase instability.

&&

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

A surface high pressure and a weak trough will cause light to
moderate east northeast winds across the region today. The modest
increase in moisture will weaken the trade wind cap inversion,
allowing for more showers formation. The focus of the strongest
activity should be in the southwestern quadrant of Puerto Rico this
afternoon, where urban and small stream flooding will be
possible. Since the winds are on the light side, showers could
drift along the Cordillera Central and last a little longer after
sunset. On the other hand, a mid-level ridge is holding at the mid
levels, maintaining dry air above 10,000 feet. Therefore, the
potential for thunderstorms will be limited.

As the surface trough continues to move west-northwest just north of
the islands, moisture will continue to flow into the northeastern
Caribbean, and the winds will shift from the southeast on Tuesday
and then from the east on Wednesday. Columnar moisture will tap
deeper into the mid-levels, allowing for a better chance of showers.
As a result, the high resolution models show an increase in shower
activity. As is usual, the pattern will favor passing showers moving
during the day over the U.S. Virgin Islands and eastern Puerto Rico,
resulting in ponding of water in roadways and low-lying areas. Then
in the afternoon, under an east to east-southeast flow, the
northwestern quadrant of Puerto Rico should see the heaviest
activity, and also from El Yunque into the San Juan metro area.
Again, the risk of urban and small stream flooding will be enhanced
on these days.

&&

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

A mid to upper-level trough moving eastward across the Caribbean
Sea will weaken the ridge aloft, amplifying over the Northeast
Caribbean through the weekend. Another ridge will build between
the mid and upper levels from Sunday onward. As a result, expect
an unstable weather pattern Thursday through at least Saturday,
with the advective pattern returning by early next week.

The weather pattern will be unstable, which may undermine the
trade wind cap, allowing vertical mixing above 700 MB through the
second half of the week. A jet stream will also arrive with the
trough aloft and hold from Thursday through early Sunday. Also,
500 MB temperatures will drop below -7 degrees Celsius, providing
better environmental conditions for the development of
Thunderstorm activity. Once again, the GFS Galvez-Davison Index
(GDI) indicates an unstable weather pattern with the potential for
scattered to numerous convective activities. Therefore,
thunderstorms will be possible each afternoon (Thursday and
Friday) and from Friday evening through at least Saturday. The
limiting factor for organized convection would be the available
moisture and the trough's final position concerning the islands.

The advective pattern will return Sunday onward, with the arrival
of passing showers across the windward sections of Puerto Rico and
the U.S. Virgin Islands, followed by afternoon convection over the
interior and western areas.
&&

.AVIATION...
(06Z TAFS)
Issued at 347 AM AST Mon Apr 17 2023

Mainly VFR conditions expected to prevail. SHRA will be moving
across the U.S. Virgin Islands this terminal from 12-16Z with brief
interruptions to operations possible. After 16Z, more significant
SHRA are expected to develop across the SW quadrant of PR. Mountain
obscurations is expected for these areas. This activity could reach
TJPS, causing brief periods of reduced VIS and low ceilings. Winds
will be out of the ENE at around 10 knots with stronger gusts.

&&

.MARINE...
Issued at 347 AM AST Mon Apr 17 2023

Marine conditions will slowly improve through the workweek. Winds
will prevail mainly from the east between 10 and 15 knots and
seas between 2 and 5 feet. The wave period will range between 6
and 8 seconds through at least Wednesday. However, a northeasterly
swell with a wave period of 10 to 13 seconds may arrive Wednesday
through Saturday without significant impact on small crafts (at
this time).

Please continue to heed caution across the surf zone along the
exposed Atlantic beaches of Puerto Rico, including Culebra and the
north and east coast in St Croix, due to possible rip current
formation.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

SHORT TERM...ERG
LONG TERM....CAM

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
430 AM AST Tue Apr 18 2023

.SYNOPSIS...
Issued at 411 AM AST Tue Apr 18 2023

A surface trough will bring some showers across the windward
sections in Puerto Rico and the U.S. Virgin Islands this morning,
and then they will spread across the rest of the islands by the
afternoon. The ridge aloft will weaken Thursday onward as a mid to
upper-level trough moves over the Northeast Caribbean, increasing
instability through early next week.

&&

.SHORT TERM...Tonight through Thursday...

A surface high pressure over the central Atlantic will maintain
moderate trade winds out of the southeast. A surface trough is
moving north of the islands, but the moisture field is reaching the
local area. This feature will bring some showers early this morning
across the Virgin Islands and eastern Puerto Rico. Then, in the
afternoon, additional showers will develop over the interior and
western Puerto Rico, and from El Yunque into portions of the San
Juan metro area. At the mid-levels, a ridge is being replaced by a
trough exiting the eastern coast of the United States. This is
allowing from the surface moisture to rise a little bit into the
column, allowing for healthier shower activity this afternoon.

As the week progresses, the mid to upper level trough will increase
instability aloft, with 500 mb temperatures cooling to around -6 to -
8 degrees Celsius. At the surface, patches of moisture will continue
to reach the area, with precipitable water values staying near
normal or just above normal. With all these ingredients combined,
the potential for isolated thunderstorms will increase as well. In
fact, thunderstorms are possible each afternoon from today through
Thursday. So far, the main risk will be periods of heavy rain that
could lead to urban and small stream flooding, as well as a slight
risk for lightning from the thunderstorms.

&&

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

The weather pattern will be unstable Friday through the weekend
due to a weak trough and a jet stream aloft. The stability
parameters may be favorable for isolated to scattered strong
convection with 500 MB temperatures dropping below -7 degrees
Celsius and steep lapse rates at low to mid levels. Once again,
the GFS Galvez-Davison Index (GDI) indicates an unstable weather
pattern with the potential for scattered to numerous convective
activities. Therefore, thunderstorms will be possible each day,
especially Friday and Saturday. Again, the limiting factors for
organized convection and widespread activity are still the high
uncertainty about available moisture (and timing) and the trough's
final position.

At this time, Sunday may be a transition day, a zonal flow will
replace the mid to upper-level trough, and the jet may move
slightly to the northeast, away from the islands. This transition
may result in the return of the advective pattern, with the
arrival of passing showers across the windward sections of Puerto
Rico and the U.S. Virgin Islands, followed by afternoon convection
over the interior and western areas.

A frontal boundary north of the area will induce a surface trough
and moisture pooling over or near the Northeast Caribbean Monday
and Tuesday. In addition, model guidance suggests a weak steering
wind flow early next week. Although there is much uncertainty
about the final location of the jet stream, if it is close enough
to Puerto Rico and the U.S. Virgin Islands, it may enhance
afternoon or evening convection each day.

&&

.AVIATION...
(06Z TAFS)
Issued at 411 AM AST Tue Apr 18 2023

Mainly VFR conditions expected to prevail. SHRA will move across the
local waters, moving over the USVI terminals and TJSJ before 14Z.
After 16Z SHRA will develop along the Cordillera Central and western
Puerto Rico, resulting in mountain obscuration. SHRA and VCTS are
expected for TJSJ and TJBQ from 16-22Z, with periods of reduced VIS
and low ceilings possible. Winds will be out of the SE at 10 to 12
knots with stronger gusts.

&&

.MARINE...
Issued at 411 AM AST Tue Apr 18 2023

Marine conditions will improve through the rest of the week.
Winds will prevail mainly from the east between 5 and 15 knots
and seas between 1 and 4 feet with occasional seas up to 5 feet.
The wave period will range between 6 and 8 seconds through at
least Wednesday. However, a northeasterly swell with a wave period
of 10 to 13 seconds may arrive Wednesday through Saturday without
significant impact on small crafts (at this time).

Beachgoers, remember that although the risk of rip currents is
low, life-threatening rip currents often occur near groins,
jetties, and piers; please exercise caution.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

SHORT TERM...ERG
LONG TERM....CAM
AVIATION...ERG

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
442 AM AST Wed Apr 19 2023

.SYNOPSIS...

A typical shower pattern will continue over the region for the next
few days. Scattered to numerous afternoon showers with isolated
thunderstorms are anticipated for interior and northwestern Puerto
Rico into the end of the week. During the overnight and morning
hours, passing showers will affect the local waters, pushing onshore
from time to time over the islands. On Saturday, a deep-layer trough
and weak frontal boundary may bring an increase in activity to the
region, as well as a shift in winds, pushing shower activity more
towards northern and eastern Puerto Rico during the afternoons for
the end of the week.

There is a moderate risk of rip currents for most local beaches.

&&

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

A surface high pressure will drive east southeast winds across the
islands through Friday. Embedded in the flow, patches of moisture
will move into the islands at times. At the mid to upper levels, a
ridge to the northeast of the Lesser Antilles is maintaining a dry
air mass above 700 mb, trapping all the moisture below these levels.
The ridge will be replaced by a trough exiting the eastern coast of
the United States. From this trough, a surface low pressure will
develop near the Bahamas, and its moisture field could approach the
region by late Friday. The mid to upper level trough will act to
gradually increase instability aloft, with 500 mb temperatures
cooling down to around -7 to -8 degree Celsius. In general, the
pattern should not change too much from what has been observed in
the past few days. The local effects will combine with the available
moisture to generate afternoon convection, with the potential for
isolated thunderstorms each day. The main focus of the rain should
be the interior and western Puerto Rico, and from El Yunque into the
San Juan metro area. The risk for urban and small stream flooding,
or at the very least, ponding of water on roadways and low-lying
areas will persist throughout the period.

&&

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

On Saturday morning, a frontal boundary is forecast to be northwest
of the region, associated with a low within a deep-layer trough to
the north of Hispaniola. This will bring an increase in moisture to
the region, as well as an increase in instability, particularly for
Saturday, but likely also for Sunday as well. Furthermore, this will
result in a weak steering flow over the area. Some shallow
southeasterly winds may persist below around 850 hPa through part of
the day on Saturday, but above that, winds are forecast to be
generally westerly. An upper-level jet above around 250-300 hPa,
with speeds of around 65 to 80 knots is also forecast to be over the
region, contributing to further instability over the area. Overall,
active weather is likely on Saturday, particularly during the
afternoon. Because of the light steering flow which is forecast to
be predominantly out of the west to west-southwest, the areas most
likely to see convective activity are interior Puerto Rico,
especially along and near the Cordillera, and eastern and
northeastern Puerto Rico. These conditions will likely persist into
the early part of next week, with moisture lingering into Monday,
and the overall steering flow maintaining a westerly to
southwesterly component. Instability will gradually decrease,
though, which will likely result in a decrease in shower activity.


Moisture will decrease, as will instability, with ridging over the
area for Tuesday through midweek. The overall flow will return to
a more easterly to southeasterly, though there will remain
westerly winds above around 700 hPa. A fairly typical pattern is
likely to prevail during this time, though showers are likely to
be slow- moving, and may be pushed back over to where they were
initially generated as they develop further and reach the
westerlies aloft. Looking forward, model guidance suggests that
there may be another frontal boundary that could impact the region
late in the week, but forecast confidence is low.

&&

.AVIATION...
(06Z TAFS)

Mainly VFR conditions expected to prevail. SHRA are expected to
develop after 16Z for the Cordillera Central and northern sections
of PR. The activity will reach TJSJ and TJBQ terminals, with
brief periods of reduced VIS and low ceilings possible. Winds will
pick up after 14Z, out of the ESE at 10-14 kts, and stronger
gusts.

&&

.MARINE...

Seas of less than 5 feet will persist across the waters. Winds
continue out of the east at around 10 to 15 knots, and up to
around 15 to 20 knots, mostly for nearshore waters, which will
maintain some choppy conditions. Operators of small craft should
exercise caution.

There is a moderate risk of rip currents for most local beaches. For
tomorrow, the risk may increase to high for beaches of north central
Puerto Rico; regardless, beachgoers should maintain situational
awareness and remain cautious for the potential for life-threatening
rip currents.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

SHORT TERM...ERG
LONG TERM....CRS
AVIATION...ERG

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
407 AM AST Thu Apr 20 2023

.SYNOPSIS...
Showers will continue to develop in the afternoon for northwestern
Puerto Rico. A surface low pressure will develop north of the
area. This system will increase the potential for stronger showers
for Friday and the upcoming weekend, with an enhanced risk for
flooding. Conditions are expected to dry by early next week, but
then very warm conditions are anticipated.


&&

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

Patchy moisture is affecting the region, supporting shower activity
in a typical pattern. There is a patch of moisture currently over
the east, which is promoting some passing shower activity over the
waters, some of which has moved onshore, particularly in
eastern/northeastern Puerto Rico. There remains decent stability
over the area, with ridging aloft. The steering flow remains east-
southeasterly over the region today into tomorrow. As such, the
shower pattern will be passing showers in the east during the
overnight and morning hours, and convection affecting interior and
western/northwestern Puerto Rico. Thunderstorms are not anticipated.

Tomorrow into Saturday, a surface low is forecast to develop to the
north of Hispaniola, associated with a deep-layer trough that is
approaching from the northwest. Instability will gradually increase
late tomorrow, with a greater increase on Saturday. An approaching
frontal boundary will also bring an increase in moisture to the
region, particularly on Saturday. The steering flow will be
substantially weakened, though, and therefore showers and
thunderstorms that are expected to develop will be quite slow
moving. There is very limited wind forecast below 850 hPa (not
including the gusty surface winds that are likely in and around
showers and thunderstorms). This decrease begins on Friday, and on
Saturday light winds with a westerly component are expected in the
lower levels. Above 850 hPa/4500 ft, winds will be westerly, with
increasing speed with height; a jet is forecast to be over the
region at around 250 hPa, with speeds of around 80 kts. Though
thunderstorms are not expected to be especially strong (which is not
to say that there will be no strong thunderstorms), locally high
rainfall totals are possible, owing to the likelihood of periods of
heavy rain and the slow movement of showers and storms. WIth winds
increasing with height, the stronger showers are more likely to
drift eastward or northeastward. As such, the focus of afternoon
activity for Saturday is likely to be interior Puerto Rico, and into
eastern Puerto Rico.

&&

.LONG TERM...Sunday through Friday...
A surface low pressure north of the islands will maintain a light
wind flow out of the west over the islands. The lingering moisture
will continue to generate afternoon showers across eastern Puerto
Rico, Vieques, Culebra and over and around the Virgin Islands.
These showers could be strong at times, leaving ponding of water
on roadways and low-lying areas. The low pressure will weaken and
should approach the area, shifting the winds from the northwest,
and then from the north by Monday and Tuesday. A dry air slot is
expected to move in during this period, so conditions should dry
out.

By Tuesday and into the later part of the workweek, a high
pressure at the low to mid-levels will get established just
northeast of the islands and then it will migrate/reform just east
of the Lesser Antilles. As a result, the trade winds will
reestablish from the southeast, but with a flow extending all the
way into 700 mb. Moisture content is expected to be limited during
this period, with precipitable water values below normal levels.
However, temperatures will warm, likely reaching the low 90s, and
heat indices surpassing the 100 degree mark in low-elevated and
urban areas. At the end of the period (Thursday through Friday),
moisture will increase once again from the south, increasing the
potential for showers, first for St. Croix and making it way up
into the northern islands and eastern Puerto Rico.


&&

.AVIATION...
Generally VFR conds expected next 24 hrs for all aerodromes. Passing
SHRA over the waters through the morning, which may push onshore
from time to time; little to no operational impacts expected for
nearby terminals of TJSJ/TIST/TISX. Afternoon SHRA expected interior
into W/NW PR, with impacts possible for TJBQ. Streamer may also
develop in east, and could affect TJSJ/vc.

&&

.MARINE...
A small northerly swell will continue to invade the local waters.
Seas are expected to remain at 3 to 5 feet, however. Marine
conditions are expected fairly tranquil by the end of the workweek
and early of the weekend as winds subside. The northerly swell
will maintain a high rip current risk for north-central and
northwestern Puerto Rico through tonight, and a moderate risk for
Culebra, St. Thomas and St. John.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...

PR...High Rip Current Risk through this afternoon for PRZ005-008.

VI...None.
AM...None.
&&

$$

SHORT TERM...CS
LONG TERM....ERG

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
400 AM AST Fri Apr 21 2023

.SYNOPSIS...
A mid to upper level trough and associated surface low pressure
will bring an increase in showers for Friday and the weekend.
Winds will become light as well, and out of the west, so the main
focus of rain will be eastern Puerto Rico rather than the west.
The risk for urban and small stream flooding will remain elevated
during this period. The weather will improve by early next week,
but temperatures will also become warmer, with heat indices around
100 degrees.


&&

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

Patchy moisture continues to affect the region, sustaining shower
activity over the area. This morning, there is a patch of enhanced
moisture to the north/northeast of the islands that is causing
scattered showers across the Atlantic waters, some of which have
made their way onshore from time to time. This will continue this
morning, though the patch is moving away from the area, and
therefore the potential for showers will decrease over the next
several hours. The steering flow at the moment is out of the east-
southeast. However, a frontal boundary is approaching from the
northwest, associated with a developing low to the north. This will
bring an increase of moisture, with the bulk of the increase seen
tonight into tomorrow. However, this will also result in veering
winds. Winds above around 700 hPa are out of the west, based on the
0Z sounding, with generally east-southeast flow below that. These
lower level winds are forecast to shift, particularly after around
midday, becoming more southerly by late afternoon and then
southwesterly tonight. As such, shower activity is likely to affect
the interior portions of Puerto Rico more than elsewhere, though
some are likely to drift into northwestern Puerto Rico earlier in
the afternoon, and into northern, particularly north central, Puerto
Rico later in the afternoon. This developing low is in a deep-layer
trough which will provide instability to the region starting today
and likely into Sunday. A 70 knot jet is also forecast to be over
the region at around 250 hPa, which will also aid in instability
over the islands. Increasingly active weather is expected, with a
marked increase in moisture likely to reach the northern islands by
tomorrow morning. Showers and thunderstorms are expected to develop
over the interior of Puerto Rico tomorrow afternoon, drifting
eastward/east-northeastward. The steering flow will be relatively
light, with winds less than 20 knots below around 13k feet. This
will result in slow-moving showers, though some of the strongest
showers are likely to pick up a little bit of speed once they've
developed, and because of this, locally high rainfall totals are
anticipated. Impacts may be seen in the San Juan metro area; urban
and small stream flooding is a concern, and localized flash flooding
cannot be ruled out.

Moisture will linger over the area on Sunday, as will instability. A
decrease in shower activity is expected, but overall active weather
is still expected. The steering flow will be westerly to west-
northwesterly. This will result in the peak in rainfall activity
being over interior and eastern Puerto Rico, with some showers
making their way into southeastern Puerto Rico.

&&

.LONG TERM...Monday through Saturday

The surface low pressure will be digging into the islands on
Monday, while the edge of the associated upper mid to upper level
trough will be crossing the Lesser Antilles. Puerto Rico and the
U.S. Virgin Islands will be in an unfavorable area for strong
shower development. In fact, as the low get closer, a drier air
mass will filter into the region, limiting the formation of
showers. On Monday, the winds will be coming out of the north due
to the circulation of the surface feature. By Tuesday, the low
opens and the wind flow will recover a more typical pattern,
coming out of the east to east southeast. Then, a surface high
pressure east of the Leeward Islands will drive an area of
enhanced moisture into the northeastern Caribbean. There is some
discrepancies between the global models on whether the bulk of
the moisture will actually reach the local islands, or it will
stay mainly to our east. This add some uncertainty to the
forecast, but for now the official forecast is a compromise
between the guidance. Some showers can be expected to be dragged
by the winds, reaching the Virgin Islands and the southern coast
of Puerto Rico, then with additional activity firing up in the
northern portions of the area in the afternoon. Additionally,
under a southeasterly humid flow, heat indices are expected to
climb just above 100 degrees, and even a few degrees higher on
Friday.

&&

.AVIATION...
Generally VFR conds expected next 24 hours for all terminals.
Afternoon SHRA/TSRA over interior and northwestern PR, with impacts
for TJBQ possible; the risk decreases late in the afternoon as SHRA
will likely drift to over north central PR. Streamers expected in
the east, with limited potential for impacts to TJSJ. Tonight,
increasing SHRA/TSRA expected over Atlantic. Cannot rule out impacts
for TJSJ, and TIST/TJBQ to lesser extent.

&&

.MARINE...
There is a small northerly swell affecting the water and
additional pulses will continue to reach the islands this week.
However, seas will remain below 5 feet. Winds will up to 15 knots
today, but will be slowing down throughout the weekend, and
switching from the west. There is a moderate rip current risk for
the north-facing beaches.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

SHORT TERM...CS
LONG TERM....ERG

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
441 AM AST Sat Apr 22 2023

.SYNOPSIS...

Today, expect the surface induced low and mid-level trough
northwest of Puerto Rico to continue approaching the area through
the weekend. This weather pattern will increase the potential for
stronger showers during the weekend, with an enhanced risk for
flooding. The weather will improve by early next week as drier air
moves in across the region.

&&

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

A surface low is located about 600 miles north-northwest of the
islands. This is resulting in weak surface winds over the region. It
is also associated with a frontal boundary that is now just
north/northwest of the islands, promoting increased moisture over
the area. Aloft is also a deep-layer trough, as well as an upper-
level jet around 250 hPa with speeds of around 70 kts. As such,
there is good instability over the area today. Passing showers will
continue over the waters this morning, pushing onshore from time to
time. This afternoon, showers will develop over the interior of
Puerto Rico, primarily along the mountains, with the initial focus
along the Cordillera Central. Showers and thunderstorms will drift
generally eastward/northeastward, with the stronger storms meeting
with the stronger winds aloft, and therefore those are the ones most
likely to reach eastern and northeastern Puerto Rico and beyond.
Rainfall totals of around 1 to 3 inches are expected in the affected
areas, but locally higher amounts are possible. Flooding is a
concern, mostly in the form of minor and urban and small stream
flooding, but some flash flooding is possible.

Moisture persists tomorrow, as well, with the bulk of the moisture
from the frontal boundary remaining over or near the islands, moreso
in the south and east. Furthermore, a shortwave trough aloft will
bring a resurgence in instability following a decrease overnight.
Overall, a decrease in shower and thunderstorm activity is expected
for Sunday compared to today, but still it will be an active day.

During the overnights and mornings, the passing showers are more
likely to affect western and northwestern Puerto Rico. Through
Sunday night, activity will decrease as drier air moves into the
region. Much less active weather is expected for Monday.

&&

.LONG TERM...Tuesday through Sunday...

No significant changes have been introduced into the current
forecast. On Tuesday, as the low-pressure surface system opens,
expect a more typical weather pattern of occasional morning
showers across the east and afternoon convection across the
interior and western quadrant of Puerto Rico and the U.S. Virgin
Islands. This weather feature will be followed by a high surface
pressure system east of the Leeward Islands. The high pressure is
forecast to bring an area of enhanced moisture into the
northeastern Caribbean. The moisture content will remain below
normal to around normal climatological levels. Precipitable water
model at all levels shows most PWAT values below the 700mb through
at least Saturday. By the end of the weekend, models are showing
some discrepancies in the forecast. Therefore, the long-term
period remains under revision.

&&

.AVIATION...Overall VFR conds expected for terminals today. SHRA/TSRA
developing over interior PR, esp Cordillera Central, and into NE
and N central PR. Could see MVFR or worse at TJSJ, with lower risk
for MVFR at TJPS/TIST. Terrain obscurations likely. Low risk for
impacts in afternoon for TJBQ/TISX. Passing SHRA/TSRA tonight over
the waters, moving onshore in W and NW PR. Cannot rule out MVFR
for TJBQ, mostly betw 23/02Z & 23/10Z. Winds light to around
FL050, except in/near SHRA/TSRA.

&&

.MARINE...Small craft operators can expect winds out form the
south around 5 and 10 knots with ocasional seas up to 5 feet. The
small northerly swell continues to propagate across the Atlantic
Ocean and Caribbean Passages. The risk of rip currents is moderate
along the north- facing beaches in Puerto Rico, St Croix and
Culebra.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

SHORT TERM...CS
LONG TERM....MMC