Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
414 AM AST Sun Apr 23 2023

.SYNOPSIS...

Today, expect unstable weather conditions across the local
islands. The potential for stronger showers and isolated
thunderstorms today remains, 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 Tuesday...

Satellite imagery suggests that the peak in moisture from the
frontal boundary is over the region this morning, which is resulting
in showers across much of the waters, some of which have pushed
onshore from time to time. A few thunderstorms have also been seen
off and on through the night, though they have been brief. A mid-
level trough and surface low are over the region, resulting in
instability. At the upper-levels, though, the jet around 250 hPa has
weakened over the islands; the 0Z sounding showed that there was
already some modest weakening of the jet compared to the 12Z
sounding yesterday morning. Overall, this setup is conducive for
active weather yet again today. The steering flow remains weak, but
is somewhat westerly, and is expected to become more northwesterly
this afternoon. As such, the focus of showers and thunderstorms will
be in the interior of Puerto Rico into eastern and southeastern
portions of the island. Showers will be relatively slow-moving,
especially as they initially form. Because of this, locally high
rainfall totals are possible again today.

Dry air moves into the region tonight. Decreasing shower activity is
expected through the night. For Monday and Tuesday, drier-than-
typical conditions are expected. Some showers are still possible,
but overall will be limited. The (weak) steering flow for Monday is
roughly northwesterly, putting showers over interior and
southeastern Puerto Rico. On Tuesday, the steering flow is likely to
shift through the day, from northerly to roughly east-northeast,
while remaining quite weak. Showers over the interior of Puerto Rico
may also spread to over southern and southwestern Puerto Rico. With
winds above around 850 hPa remaining westerly to west-southwesterly,
some showers may also drift into eastern or northeastern Puerto
Rico.

&&

.LONG TERM...Wednesday through Monday...

Model guidance continues to suggest the typical weather pattern
from midweek into Thursday, with occasional morning showers over
the east and some afternoon convection across the west and
interior sections of Puerto Rico and the U.S. Virgin Islands. At
this time, precipitable water models keep all the moisture below
700mb, meaning that any rainfall activity that does develop will
be limited to moderate and not significant. Nonetheless, by the
end of the workweek, a surface high-pressure system will position
across the forecast area, generating a southeasterly flow across
the islands. The high surface pressure will pull tropical moisture
into the region. However, moisture conversion is likely during the
weekend due to a boundary to the north of the area that will mess
with the wind flow. From Friday into Sunday, PWAT models suggest
moisture slightly surpassing the 700 mb, meaning that moderate to
heavy rainfall activity is likely, and possible isolated
thunderstorms cannot be ruled out. During the weekend, expect an
increase in humidity and precipitable water values around normal
to above-normal climatological levels. Latest guidance suggests
that weather conditions will improve by the beginning of the week
as drier air moves in across the region.

&&

.AVIATION...Generally VFR conds are expected for the next 24 hours
at most aerodromes. SHRA w/ TSRA poss continue over the waters
this morn. Cannot rule out brief MVFR or worse for TJBQ. PM
SHRA/TSRA expected for interior PR into E/SE PR & nearby islands.
Brief MVFR or worse cannot be ruled out for TJSJ/TJPS/TISX. MVFR
poss for TIST this eve. Activity decreases tonight throughout
region, but may linger VC St. Croix, with potential impacts for
TISX.

&&

.MARINE...Small craft operators can expect winds out from the
northwest at 5 to 10 knots with ocasional seas up to 3 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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
359 AM AST Mon Apr 24 2023

.SYNOPSIS...

A dry air mass has moved over the islands. Nonetheless, today,
the weather conditions will be variable. Expect a combination
cloudy and sunny skies at times. However, we cannot ruled out
afternoon convection across the interior portions of Puerto Rico
today. Soils are saturated, and some rivers are running slightly
high; thus, persistent heavy rain could produce sudden mudslides
or urban flooding.

&&

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

Afternoon moderate to locally heavy rains will support limited to
elevated excessive rain hazard risk today.

Despite weakening and drifting further to the east, a surface low
pressure and mid-level trough will maintain marginally unstable
weather conditions today. In the meantime, winds will slowly become
more northerly but still weak at 5-10 mph, induced by the same
surface feature. Under this flow, drier air will be steered into the
region, limiting shower development and making it much quieter than
yesterday. However, as local effects and diurnal heating becomes
influential in the afternoon, expect shower development along the
Cordillera Central into southern Puerto Rico. Rainfall totals from
moderate to locally heavy rains, with isolated amounts of an inch or
higher, could lead to urban and small stream flooding to localized
flash flooding, particularly in areas affected by yesterday's rains.

For Tuesday and Wednesday, weather conditions will stabilize with
the additional entrance of drier air and unfavorable conditions for
deep convective development. Yet, afternoon shower development is
still likely along the interior each day. Winds remain calm to light
but will become variable on both days, with no clear steering
pattern.

Daily temperature variations will range from the upper 80s to around
90 degrees across coastal and other urban areas in the daytime to
the upper 50s to about 60 degrees across higher elevations.

&&

.LONG TERM...Thursday through Tuesday...

The current forecast leans towards typical weather conditions on
Thursday. Nonetheless, expect occasional morning showers over the
east and some afternoon convection across the west and interior
sections of Puerto Rico and the U.S. Virgin Islands. Models still
keep all the moisture below 700mb, meaning that any rainfall
activity that does develop will be limited to moderate and not
significant. By the end of the workweek, the Bermuda high will
move east-southeastward, resulting in the winds shifting to become
more southeasterly, bringing tropical moisture up over the
islands. This will likely result in some moisture convergence over
the weekend as a weak frontal boundary located to the north of the
region halts the progression of the moisture away from the area.
At this time, there is some uncertainty between the GFS and ECMWF
models for the later part of the workweek into the weekend. The
forecast for this part of the period leans more toward what the
GFS model suggests. From Friday into Sunday, PWAT models suggest
moisture surpassing the 700 mb, meaning that moderate to heavy
rainfall activity is likely, and possible isolated thunderstorms
cannot be ruled out. During the weekend, expect an increase in
humidity and precipitable water values around normal to above-
climatological-normal levels.Latest guidance suggests around 1.70
to 1.80 inches of precipitable water content available across the
forecast area by the beginning of the workweek. However, the long-
term forecast remains under revision due to the uncertainty of the
models.

&&

.AVIATION...Mainly VFR conditions will prevail across most
terminals. Brief MVFR conditions are possible with passing SHRA
across USVI terminals through 24/14Z. Afternoon SHRA could cause
MVFR at TJSJ and TJPS between 24/16-22Z. Calm to light and variable
winds becoming more northerly with sea breeze variations and
increasing to 10-15 mph after 24/14Z. Winds become light and
variable after 24/22Z.

&&

.MARINE...Seas will remain relatively calm today around 2 to 4
feet with north winds 5 to 10 knots. 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...ICP
LONG TERM....MMC

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
335 AM AST Tue Apr 25 2023

.SYNOPSIS...

Again marginal instability and enough low-level moisture will
continue to promote shallow convective activity each afternoon
through at least Wednesday. However, coverage will be reduced as
moisture content is expected to further decrease.

&&

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

Afternoon moderate to locally heavy rains could lead to limited to
elevated excessive rain hazard risk each afternoon.

A broad but weak mid-level trough pattern persists over the North
Atlantic into the northeastern Caribbean, maintaining marginally
unstable weather conditions with slightly cooler than normal mid-
level temperatures and weak trade wind cap inversion. Despite the
influence of drier air at the mid-levels, which should support
generalized fair weather conditions, expect afternoon showers with
isolated thunderstorms development aided by local effects and
diurnal heating each afternoon. The focus of the activity and the
resulting rainfall totals will depend on the predominant wind flow,
influenced by a surface high pressure over the western Atlantic and
north of the region through Wednesday and a surface-induced trough
to the northwest on Thursday. The expected east-southeast winds at 5-
10 mph today suggest the bulk of the activity will favor the
interior to northern sections of Puerto Rico, where isolated
rainfall totals could exceed two inches from slow-moving showers
producing moderate to locally heavy rains. As a result, limited to
elevated excessive rainfall hazard risk levels are likely, leading
to urban and small stream flooding. Isolated flash flooding is
possible.

As winds gradually back from the east on Wednesday and more east-
northeast on Thursday, the activity focus will likely shift from the
interior and western Puerto Rico on Wednesday to the interior and
southwestern Puerto Rico on Thursday. Equally, rainfall totals from
moderate to locally heavy rains could lead to limited to elevated
excessive hazard risk levels each afternoon, particularly in areas
affected by the previous day's rains.

Daily temperature variations will range from the upper 80s to around
90 degrees across coastal and other urban areas in the daytime to
the upper 50s to about 60 degrees across higher elevations.

&&

.LONG TERM...Friday through Wednesday...

By the end of the workweek, the Bermuda high will move east-
southeastward, resulting in the winds shifting to become more
easterly, bringing tropical moisture up over the islands. This
will likely result in some moisture convergence over the weekend
as a weak frontal boundary located to the north of the region
halts the progression of the moisture away from the area. At this
time, there is some uncertainty between the GFS and ECMWF models
for the weekend. The forecast for this part of the period leans
more toward what the GFS model suggests. Early in the weekend into
late Monday, PWAT models suggest moisture surpassing the 700 mb,
meaning that moderate to heavy rainfall activity is likely, and
possible isolated thunderstorms cannot be ruled out. On Saturday,
expect an increase in humidity and precipitable water values to
above-climatological-normal levels. Latest guidance suggests
around 1.70 to 1.80 inches of precipitable water content available
across the forecast area by the beginning of the workweek. At
this time, Tuesday looks like a transition day. By mid- week,
weather conditions will improve as drier air moves across the
region. However, the long-term forecast remains under revision due
to the uncertainty of the models.

&&

.AVIATION...Mainly VFR conditions will prevail across most
terminals. However, afternoon SHRA could result in brief MVFR
conditions across all PR terminals between 25/16-22Z. Calm to light
and variable winds becoming more east-southeasterly with sea breeze
variations and increasing to around 5-10 mph by 25/18Z. Winds again
become light and variable after 25/22Z.

&&

.MARINE...Mariners can expect seas around 4 feet or less and
winds out of the east at 5 to 10 knots across the local waters.

Beachgoers, the risk of rip currents is moderate along the north-
facing beaches today. Nonetheless, the north central beaches may
experience high rip current risk on Thursday.

&&

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

$$

SHORT TERM...ICP
LONG TERM....MMC

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
402 AM AST Wed Apr 26 2023

.SYNOPSIS...

Today, winds out of the east will promote passing showers across
the windward portions of the islands at times. Due to the
sufficient amount of low- level moisture and local effects,
convective activity is expected each afternoon across the central
and western portions of Puerto Rico.

&&

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

Afternoon moderate to locally heavy rains could lead to limited
excessive rain hazard risk each afternoon, mainly across the
interior to northern sections of Puerto Rico. Limited excessive heat
hazard risk levels are likely each afternoon.

Although drier air and trade wind cap inversion hold a stable layer
above the 600-700 mbar layers, a weak trough pattern will maintain
marginally unstable weather conditions below this layer while
yielding to a westerly to southwesterly mid-level flow. A light
surface steering flow at 5-15 mph will persist through the cycle,
shifting from the east-southeast today to more east on Thursday and
Friday. Under this flow, moisture advection will cause precipitable
water values to briefly reach above-normal seasonal levels today and
Thursday, followed by some drying on Friday with the entrance of
drier air. Despite these variations, low-to-mid-level conditions
will favor local effects and diurnal heating to trigger shower
development each afternoon, with generally fair weather conditions
during the overnight and morning hours. Since the focus of the
afternoon activity and rainfall distribution will depend on the
prevailing steering flow, expect the bulk of the activity to focus
along the interior to northern sections, including portions of the
San Juan metropolitan area influenced by the mid-level flow.
Moderate to locally heavy rains from slow-moving showers, generating
isolated rainfall totals that could exceed an inch, could lead to
limited excessive rainfall hazard risks and possibly urban and small
stream flooding.

Daily temperature variations will range from the upper 80s to around
90 degrees across coastal and other urban areas in the daytime to
the upper 50s to about 60 degrees across higher elevations.

&&

.LONG TERM...Saturday through Thursday...

For the weekend, expect the Bermuda high to continue moving east-
southeastward, resulting in the winds shifting more easterly with
a southeasterly component, bringing tropical moisture up over
Puerto Rico and the U.S. Virgin Islands. This will likely result
in some moisture convergence as a weak frontal boundary located to
the north of the region halts the progression of the moisture away
from the area. At this time, there still is some uncertainty
between the GFS and ECMWF models for the beginning of the
workweek. The forecast for this part of the period leans more
toward what the GFS model suggests. Late Monday into Tuesday,
precipitable water models show moisture surpassing the 700 mb,
meaning that moderate to heavy rainfall activity is likely, and
possible isolated thunderstorms cannot be ruled out. At this time,
Tuesday looks like the best workweek day, with the better
available moisture for showers to develop. Overall, expect an
increase in humidity and precipitable water values to flip-
flopping between normal and above-climatological-normal levels
from the beginning of the weekend into the workweek. Nonetheless,
weather conditions will improve by mid-week as drier air moves
into the region.

&&

.AVIATION...Mainly VFR conditions will prevail across most
terminals. However, afternoon SHRA could result in brief MVFR
conditions across all TJSJ and TJBQ terminals between 26/16-23Z.
Calm to light and variable winds becoming more east-southeasterly
with sea breeze variations and increasing to around 5-15 mph by
26/18Z. Winds again become light and variable after 26/23Z.

&&

.MARINE...Mariners can expect seas of 5 feet or less and winds
out the east around 5 to 10 knots across the local waters. A
small northeasterly swell will continue spreading across the
Atlantic Ocean.

Beachgoers, the risk of rip currents is moderate along the east
and north-facing beaches. However, a high risk of rip current is
possible from Thursday night into Friday.

&&

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

$$

SHORT TERM...ICP
LONG TERM....MMC
AVIATION...MMC/ICP

[cycloneye]

Area Forecast Discussion...DELAYED
National Weather Service San Juan PR
531 AM AST Thu Apr 27 2023


.SYNOPSIS...
Showers and a few thunderstorms can be expected during afternoon
hours both today and tomorrow Friday. This will promote flooding
of urban areas and small streams in localized areas. More stable
weather conditions is anticipated for the weekend. A small
northerly swell will promote a high risk of rip currents for
north-facing beaches of Puerto Rico today and tonight.


&&

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

While higher pressure is found north of the area at the surface in
the western Atlantic, a weak low-level trough is moving slowly west
northwest through the area. A band of moisture moved across Puerto
Rico and the U.S. Virgin Islands from the south overnight and is now
moving into the Atlantic waters. This has brought scattered showers
to the area waters. Flow is generally easterly at lower levels, but
highly influenced by land and sea breezes. Flow at 850 mb however,
is light, somewhat variable, but generally from the southeast. This
will cause flare ups of convective activity each day over the
interior and western portions of Puerto Rico with some streamers off
Culebra, Vieques and the U.S. Virgin Islands during the afternoons.
The GFS shows this convective activity pushing northeast toward the
greater Bayamon and San Juan Metropolitan areas later in the
afternoon at least for today. 500 millibar temperatures are not too
favorable to thunderstorms. And, although a few did occur along the
north coast of the Dominican Republic yesterday, none were observed
in Puerto Rico. Today will be somewhat wetter and a slight chance of
thunderstorms was left in the forecast in the areas with heavier
showers. Tomorrow the 500 mb temperature will dip somewhat and a few
thunderstorms are possible in the western and interior sections of
Puerto Rico. More stable conditions are expected on Saturday. Some
flooding of urban areas and small streams is possible in localized
areas today and Friday, but conditions become less favorable on
Saturday.

At upper levels a weak trough passes north of the area today and
Friday, but a ridge builds over the area on Saturday to cause more
the atmosphere to become more stable.

&&

.LONG TERM...Sunday through Friday...

For the most part, a seasonal weather pattern can be anticipated for
most of the long-term period, with moisture content fluctuating from
below-normal to near-normal levels. Tuesday will be the driest of
the forecast period, with precipitable water values decreasing to as
low as 1.10 inches and 700-500 mb relative humidity plummeting to
below 15%. Dynamically stable conditions will persist as a surface
high pressure and a mid to upper-level ridge build across the local
area by Sunday through midweek. So far, the forecast calls for
mainly fair weather conditions with limited shower activity across
the local islands. However, locally induced afternoon showers will
remain possible through at least Wednesday but should be focused
mainly on portions of interior and western/northwestern Puerto Rico.
Much warmer temperatures can be expected by Monday, persisting
through the rest of next week, as winds become more southeasterly.

By Late Wednesday and through at least Friday, model guidance
suggests a shift in the weather pattern due to a building mid- to
upper-level trough just north of the region and increased moisture
convergence as the associated frontal boundary approaches from the
northwest. The prevailing winds will continue southeasterly,
resulting in a warmer and much moister environment, as low-level
moisture returns and the upper trough crosses just north of the
region. This scenario will result in marginally unstable weather
conditions and slightly cooler temperatures aloft. Therefore,
expect a gradual transition to a wetter weather pattern with some
instability aloft at least through Friday, with the potential for
enhanced shower and isolated thunderstorm development across the
islands and coastal waters. The potential for urban and small-
stream flooding will increase, particularly during the afternoon
hours.

&&

.AVIATION...Mainly VFR conditions will prevail across most
terminals. However, afternoon SHRA/isold +TSRA could result in brief
MVFR conditions with mtn topping across the western and interior
areas of PR between 27/17-23Z. Light land breezes will give way to
sea breezes of 5-15 knots aft 27/13Z in east southeasterly flow.
Winds again become light and variable after 27/23Z. Maximum winds
W=WNW 40-50 kts btwn FL260-520.

&&

.MARINE...A small northerly swell will continue to invade the local
waters. However, mariners can expect seas of 5 feet or less and
winds out the east around 5 to 10 knots across the local waters. The
swell will cause a high rip current risk for northern Puerto Rico on
today and tonight.

&&

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

High Rip Current Risk from this evening through late tonight for
PRZ008.

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

$$

SHORT TERM/AVIATION...WS
LONG TERM/MARINE...CVB

[cycloneye]

Area Forecast Discussion...DELAYED
National Weather Service San Juan PR
521 AM AST Fri Apr 28 2023


.SYNOPSIS...

Afternoon showers are likely each afternoon, affecting mostly
interior and western/northwestern Puerto Rico and, at times, the
San Juan Metropolitan area. Heat indices of 102-107 degrees are
likely each afternoon, primarily across northern and western
sections. Increasing winds and a small northerly swell will yield
life-threatening rip currents early next week.

&&

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

While moisture lingered over Puerto Rico and the U.S. Virgin
Islands, showers continued over eastern Puerto Rico, north of Saint
Thomas and Saint John and around Saint Croix. The heaviest
accumulations were found on the coasts of Rio Grande and Luquillo
where 1 to 2 inches were seen. Most of the showers just before dawn
were over the Caribbean waters, and the eastern coast.

High pressure over the western Atlantic north of the area is wedging
between two lows: one over north Carolina and the other about 1450
miles north northeast of San Juan. A weak trough over the Leeward
Islands is maintaining light flow from the east northeast over the
local area. Moisture extends only up to about ten thousand feet with
precipitable water values at 1.6 inches. CAPE surpassed 2000 J/Kg
for the first time in many days last night. This allowed for the
vigorous showers of Thursday and will continue to contribute to
shower activity on Friday. Flow will continue from the east
northeast for now but developing sea breezes will cause another
difficult to predict rain pattern over the area as occurred
yesterday. Nevertheless, the models are suggesting that the best
activity will occur in the northwest quadrant of Puerto Rico this
afternoon. With 500 mb temperatures reaching their low for the week
early this morning and then rebounding during the day, it again
looks like little thunderstorm activity will ensue. Only one or two
strokes were detected in interior Puerto Rico on Thursday. The
precipitable water will peak this evening at close to two inches and
slowly sag to around 1.5 inches Sunday night. 1000 mb temperatures
will also warm in response to flow that will edge slightly toward
the southeast. Showers will continue through the period, but
Saturday and Sunday should see less intense showers with diminishing
amounts. Some localized ponding in poor drainage areas are still
expected.

&&

.LONG TERM...Monday through Saturday...

Dynamically speaking, forecast continues on track with a building
mid-to-upper level ridge over the region holding through at least
midweek. This should promote some stability aloft and limit deep
convective activity. By the end of the workweek, a polar trough will
deepen north of the local islands, gradually eroding the mid-level
ridge by Thursday and Friday. Dynamics are not looking impressive,
but enough to enhance vertical mixing. At the surface, a building
high pressure over the central Atlantic should promote moderate to
locally fresh ESE winds through the forecast cycle.

There are some uncertainties regarding the amount of moisture
expected across the northeastern Caribbean throughout the week. The
latest 28/00z GFS model solution is a bit wetter than the previous
model cycles with ECMWF showing an even wetter solution throughout
the long-term period. For this reason, POPs were slightly increased.
Models are consistent on the approach of the frontal boundary from
the northwest throughout the week, mostly by Thursday and Friday. As
it approaches, moisture convergence will get enhanced. However,
uncertainty lies in how close the frontal boundary will get
determining the amount of moisture that will converge across the
northeastern Caribbean.

Nevertheless, a typical weather pattern can be expected with showers
developing over the local waters while being pushed by the
southeasterly trades over windward coastal areas during night and
morning hours followed by diurnally induced afternoon showers over
west/northwest PR each day. Southern Puerto Rico and the smaller
islands will receive the least amount of rain. Shower intensity will
depend on the amount of low-to mid-level moisture across the islands
but will remain mostly shallow. By the end of the workweek into the
weekend, the potential for isolated thunderstorms will slightly
increase with the approach of the polar trough and associated
frontal boundary, although Saturday is looking a bit drier than
previous days. The 7-day average streamflows are running between
normal to well above-normal with soil saturation above 80% across
the interior and the eastern third of Puerto Rico. Additional rains
across the area in the coming days could maintain this trend into
early next week. Therefore, excessive runoff is possible with the
heaviest rains promoting urban and small stream flooding across
these areas.

&&

.AVIATION...Mainly VFR conditions will prevail across most
terminals. However, afternoon SHRA/isold +TSRA will result in
periods of MVFR/IFR conditions with mtn obscurations across the
western and interior areas of PR between 28/17-23Z. Light land
breezes will give way to sea breezes of 5-15 knots aft 28/13Z in
east northeasterly flow. Winds again become light and variable after
28/23Z exc arnd the USVI where flow will remain 4-8 knots from the
east with land breezes. Maximum winds W-WNW 50-62 kts btwn FL300-535
strongest at FL450. These winds will diminish early this morning
through tonight.

&&

.MARINE...

Tranquil marine conditions will persist for the next few days,
although a small northerly swell continues to invade the local
waters. Pulses of longer period northerly swells will invade the
local waters by early next week. This will mainly affect surf zone
conditions with north-facing beaches of the local islands yielding
life-threatening rip currents by early next week.

&&

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

$$

SHORT TERM/AVIATION...WS
LONG TERM/MARINE/PUBLIC...CVB

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
501 AM AST Sat Apr 29 2023

.SYNOPSIS...
Issued at 415 AM AST Sat Apr 29 2023

Light winds will continue for at least one more day, but moisture
will diminish somewhat. Nevertheless showers and isolated
thunderstorms will produce an elevated risk of excessive rainfall
leading to urban and small stream flooding in some areas with a
possibility of flash flooding. Moisture continues to diminish
Sunday and Monday as south flow brings warmer temperatures to the
north coast. The week will continue less moist, but afternoon
showers will be likely in the interior most days and at least
isolated in the U.S. Virgin Islands.

&&

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

A mid to upper-level ridge will continue to build from the northwest
and settle over the northeastern Caribbean this weekend through
early next week. This will partially limit weather conditions aloft
that are conducive to deep convective activity. At the low levels, a
surface high pressure will persist over the central Atlantic
generating light east-southeast winds across the local islands for
the next few days. The moisture content at low to mid-levels will
remain within climatological normals, slightly above normal at
times, during the short-term period.

The effects of the ridge, however, will be weaker today making it
the wettest day of the short-term forecast. Global and Hi-Res
models are fairly consistent with another round of moderate to
heavy rain during the afternoon hours. Moisture content and
dynamics aloft are not necessarily impressive, remaining within
seasonal normal as mentioned earlier. The major factors that will
enhance the excessive rainfall risk today are the above-normal
diurnal heating caused by southeasterly winds that could trigger
afternoon steep low-level lapse rates with strong sea breeze
convergence producing intense convection; and the light steering
wind flow across the area increasing the potential for slow-moving
showers and, therefore, high rainfall accumulations. Isolated
thunderstorms are possible with this activity. Convective activity
will cluster once again over the Cordillera Central and
northwestern portions of Puerto Rico. The San Juan Metropolitan
area could observe another active afternoon.

Model guidance suggests slightly less rainfall accumulation
compared to yesterday. However, saturated soils continue with the
7-day average of most streamflows across the eastern half running
above the 75th percentile. Therefore, there is an elevated risk of
excessive rainfall today with the potential of urban and small-
stream flooding and the possibility of flash floods across
localized areas. Mudslides and rockfalls are also possible in the
most vulnerable places. Activity will gradually diminish after
sunset with windward coastal areas observing occasional isolated
to scattered showers during overnight and morning hours. Sunday
and Monday will be less active as the mid to upper-level ridge
strengthens. However, enough low-level moisture will linger and,
in combination with aforementioned diurnal heating and local
effects, scattered to numerous afternoon showers will still
develop over the interior and northwestern quadrant of Puerto Rico
each day.

Above-normal surface temperatures and enough moisture content could
yield heat indices around 102-107 degrees, particularly across
northern and western sections of Puerto Rico each afternoon.

&&

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

High pressure at upper levels over the northern tip of Colombia
extends across the northeastern Caribbean on Tuesday, but drifts
eastward into the tropical Atlantic during the rest of the week
as a shortwave trough moves through the area on Saturday morning.
A cold front will approach the area with this trough, but will
stall around the Bahama Islands. A pre-frontal trough will cause
some additional moisture to affect the area on Friday and this is
expected to be the best rain producer of the long term period.
Drying is expected on Saturday and Sunday morning with a marked
decrease in shower activity.

Much of the week will be characterized by southeasterly flow that
will warm temperatures to above normal values later in the week
and over the weekend--especially along the north coast of Puerto
Rico. Although thunderstorms are generally not expected during
this period owing to the stability of the mid and upper levels,
isolated thunderstorms cannot be ruled out over the interior
during the afternoons Tuesday through Friday owing to intense
heating and local effects favoring convection.

&&

.AVIATION...
(06Z TAFS)
Issued at 415 AM AST Sat Apr 29 2023

Mainly VFR conditions will prevail across most terminals.
However, afternoon SHRA/isold +TSRA may result in periods of
MVFR/IFR conditions with mtn obscurations across the western and
interior areas of PR including TJBQ and TJSJ through 29/23Z. ESE
winds up to 12 knots with higher gusts and sea breezes, becoming
light and variable overnight. Maximum winds WNW 42-52 kts btwn
FL410-470, diminishing during the day.

&&

.MARINE...
Issued at 415 AM AST Sat Apr 29 2023

Winds increase somewhat tonight and Sunday and this will bring a
little more wave action. Models, however did not see any waves
as high as 6 feet during the next 6 days. Wind in the outer
Caribbean will bring higher seas by Friday in our southwestern
waters. Thunderstorm activity is possible today and next Friday,
however it will be mostly over interior portions of Puerto Rico.

&&

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

$$

SHORT TERM/AVIATION...CVB
LONG TERM/FIRE WX....WS

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
514 AM AST Sun Apr 30 2023

.SYNOPSIS...
Issued at 434 AM AST Sun Apr 30 2023

Modest surface high pressure will move into the central Atlantic
to maintain southeasterly flow across the forecast area. Although
the high will be found west northwest of the Canary Islands by
next weekend, flow will continue out of the southeast under the
ridge associated with it. Warmer temperatures are expected during
the week beginning today and peaking Monday but also on Thursday
and the following Monday. Heat advisories may be necessary Monday.
Mid level ridging will limit shower activity, but showers
associated with afternoon convection will still be heavy today,
Monday and Tuesday.

&&

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

A mid to upper-level ridge will hold through the short-term period
resulting in subsidence aloft that will persist over the local
islands through at least Tuesday. This will inhibit, to some degree,
deep convective activity, although a very isolated thunderstorm
aided by sea breeze convergence cannot be ruled out during afternoon
hours. Surface winds will continue from the east-southeast due to a
surface-high pressure anchored over the central and eastern Atlantic
Ocean. All these factors will promote above-normal maximum
temperatures for the next few days.

Precipitable water content and 700-500 mb humidity will remain
within the seasonal climatological normal. Moisture content,
however, will gradually increase on Tuesday as a frontal boundary
approaches from the northwest enhancing moisture convergence across
the local islands. Despite ridging aloft, enough low to mid-level
moisture will produce shower activity in a seasonal pattern.
Heaviest showers will form along the interior and northwestern
Puerto Rico each afternoon due to the combined high diurnal heating
and local effects. Streamer-like showers are also possible downwind
of the smaller islands and El Yunque with some affecting parts of
the San Juan Metropolitan area. During night and morning hours,
shower activity will develop over the local waters and move at times
over the eastern/southeastern portions of Puerto Rico and the local
islands. Ponding of water in roads and poorly drained areas,
together with minor urban and small-stream flooding are possible
with the heaviest activity. The NBM ensemble indicates that the
southwestern/southern coastal plains and St. Croix will receive the
least amount of rain during the short-term period.

The combination of high surface temperatures with ample low-
level moisture will produce high heat indices, particularly for
the northern and western lower-elevation areas throughout the
week, . At this time the warmest days appear to be Monday,
Thursday and the following Monday.


&&

.LONG TERM...Wednesday through Monday...

High pressure at upper levels north of Venezuela over the
southern Caribbean waters on Wednesday will drift into the western
Tropical Atlantic by Friday. A short wave trough will brush the
local area on Friday as it travels around a deeper long wave
trough in the northwestern Atlantic. High pressure in the central
Atlantic up through 700 mb will pull the remnants of an old
frontal boundary back over the area to augment showers and
isolated thunderstorms. This area of moisture will also be pulled
northwest into the area by the approach of a newer cold front
approaching Hispaniola. The moisture will be followed by drier air
over the weekend. An easterly wave passing south of the area
Sunday night into Monday should allow a partial rebound of
moisture for the local area and the reinvigoration of modest
shower activity in the local islands.

The main impact of the southeasterly flow, however, will be the
a general warming felt most strongly on the northern coasts of
Puerto Rico, where temperatures will rise into the lower 90s on
many days and heat indices in areas with the highest humidity
could surpass 108 degrees.

&&

.AVIATION...
(06Z TAFS)
Issued at 434 AM AST Sun Apr 30 2023

Mainly VFR conditions will prevail across most terminals. SHRA
will develop along the Cordillera Central, spreading into the
western and northern coasts thru 30/23z. The activity will affect
TJBQ and maybe TJSJ. Therefore, expect possible brief MVFR
conditions with mtn obscurations across western/northwestern and
interior areas of PR. Winds will continue from the ESE at 5-15 kt
but will be locally higher due to sea breeze variations and
near/in +SHRA. Maximum winds WNW 45-52 knots btwn FL420-535.

&&

.MARINE...
Issued at 434 AM AST Sun Apr 30 2023

Seas will remain 3 to 5 feet in the exposed waters around Puerto
Rico and the U.S. Virgin Islands for at least the next 5 days as
winds remain around or below 15 knots from the southeast. A
northeasterly swell of 10-12 seconds and up to 4.5 feet is
expected to arrive Monday and Monday night that will increase the
risk of rip currents to high on the north coasts of Puerto Rico.

&&

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

$$

SHORT TERM/AVIATION...CVB
LONG TERM...WS

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
445 AM AST Mon May 1 2023

.SYNOPSIS...Diurnal and local effects will promote shower
activity focused over the northwestern quadrant of Puerto Rico
during the afternoon hours. Isolated urban and small stream
flooding is possible. Light to moderate southeasterly winds and
available moisture will promote hot temperatures today,
particularly across northern and western municipalities. A Heat
Advisory was issued for the north- central municipalities of
Puerto Rico, from noon to 4 PM, as heat indices could near 110
degrees.

&&

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

A mid-to upper-level ridge is expected to hold over the Caribbean
Basin through the short term period, and a weak Saharan Air Layer
will continue to exit the area today. This will continue to promote
overall stable conditions aloft, with drier air and some haze.
Meanwhile, a weak high pressure at the surface over the central
Atlantic will continue to drift slowly eastward, promoting a light
to moderate southeasterly wind flow over the region through at least
Tuesday. Having said that, precipitable water (PWAT) content is
expected to remain at near normal values through Tuesday, as an area
of 1.50-1.60 inches of PWAT, currently between the Leewards and the
Anegada Passage is carried over the local area by the southeasterly
trades. This pattern will support hot temperatures, with heat
indices reaching the low to mid 100s, mainly along the northern and
western areas of Puerto Rico. Therefore, a Heat Advisory was issued
for the north central municipalities of PR, due to possible heat
indices nearing 110 degrees Fahrenheit.

In terms of shower activity, the combination of the sea breeze
convergence with daytime heating and the available moisture content
will trigger once again showers with periods of moderate to locally
heavy rainfall over the northwestern quadrant of PR. Elsewhere, fair
weather conditions should prevail with streamers developing downwind
of the islands. Isolated urban and small stream flooding is possible
with the afternoon showers in Puerto Rico. Similar conditions, with
an increase in areal coverage of showers is expected on Tuesday
afternoon. Another drier air mass is expected to move on Wednesday,
but shallow afternoon convection is expected over western PR.

&&

.LONG TERM...Thursday through Tuesday...

The period will start off with a surface high pressure system
over the Atlantic promoting southeasterly winds through the
region. Current model guidance suggests an increase in
precipitable water (PWAT) values for Friday, with values reaching
around 1.8 inches, slightly above normal values for this time of
the year. This will be due to moisture remnants of an old frontal
boundary being pushed back into the region by the wind flow.
Additionally, a short wave trough will also somewhat affect the
area on Friday and moisture from a more recent front will be found
to our north and northwest. The driest days, in terms of PWAT
values should be Thursday, Saturday and early Sunday, with values
reaching around to less than an inch on these days, as drier air
filters in. Overall, dry mid levels will be present throughout the
long term forecast period. Another similar increase in moisture
is suggested for late Sunday through Tuesday. Model guidance
suggests a weak wave moving south of the islands by late Sunday
and into Monday. Related to this, an area of more humid air, with
values generally between 1.5 to 1.8 inches will filter into the
islands through late Tuesday. Variations in the diurnal pattern
will depend in part on available moisture, with days with more
moisture having increased rain chances. Shower activity will
affect windward sectors of the islands during the morning and
overnight hours and, during the afternoon, diurnal and local
effects will play their part in promoting convective activity over
interior to western/northwestern Puerto Rico, with showers off of
the local islands and off of El Yunque also possible. The
southeasterly flow will promote warmer temperatures and heat
indices across the islands, with more significant increases over
northern coastal areas of Puerto Rico.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, SHRA is expected to
develop in and around TJBQ btw 17z-23z, which may cause tempo MVFR
conditions. Sfc winds ESE at 8-12 kt with sea breeze variations aft
14z, mainly along the north/west coasts. HZ due to Saharan dust will
gradually improve through the end of the forecast period.

&&

.MARINE...Generally southeast winds between 10 to 15 knots will
persist through the early part of the workweek. A weak long
dominant period northeasterly swell will begin to arrive during
the morning hours. However, seas will remain favorable for small
craft, at up to 5 feet, occasionally 6 feet, through much of the
upcoming week. Passing showers will affect the coastal waters
especially during the afternoon and overnight hours. There is a
high risk of rip currents for the beaches of northern Puerto Rico
extending from Aguadilla to Fajardo. Moderate to low risk
elsewhere.

&&

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

Heat Advisory from noon today to 4 PM AST this afternoon for
PRZ005.

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

$$

SHORT TERM...DS
LONG TERM....MRR

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
513 AM AST Tue May 2 2023

.SYNOPSIS...Stable conditions are expected through the next few
days with local effects promoting afternoon convection mainly over
areas of the interior and western Puerto Rico due to
southeasterly winds. These winds and available moisture will,
however, promote hot temperatures today, mainly along the lower
elevations of northern Puerto Rico. A Heat Advisory is in effect
for these areas from 11 AM AST to 5 PM AST. Moisture will
gradually decrease before increasing again on Friday.

&&

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

An upper level ridge over the Caribbean Basin will promote stable
conditions through the short term period. However, diurnally induced
afternoon showers are expected to develop each day over portions of
the interior and western Puerto Rico. Moisture content will
gradually erode each day, with the best precipitable water today
around 1.60 inches and dropping to near 1.00 inch on Thursday.
Therefore, showers today may produce locally heavy rainfall that
could lead to minor flooding. Otherwise, southeasterly winds and
increasing moisture today will promote hot temperatures once again,
mainly along the lower elevations of the northern coast of Puerto
Rico, where a Heat Advisory (NPWSJU) is in effect. For Wednesday and
Thursday, the apparent temperature may decrease by a few degrees,
but the heat index should remain in the low 100s along the northern
and western areas of PR. Across the USVI, mainly fair weather
conditions are expected to prevail, with the exception of a few
showers today.

&&

.LONG TERM...Friday through Wednesday...

A surface high pressure over the Atlantic will promote southeasterly
winds over the region to start the period. This wind flow will move
remnants of an old frontal boundary into the region, increasing
humidity. Southeasterly winds will also promote generally warmer
temperature and warmer heat indices across the islands. Current
model guidance suggest that humidity from this moisture will
increase precipitable water (PWAT) values to normal to slightly
above normal values for this time of the year. Moisture from a more
recent frontal boundary will also be found north of the islands. A
shortwave trough will also affect the area on Friday. A drying trend
is expected through the weekend, with PWAT values reaching around to
less than an inch, as drier air filters in. Dry mid levels will be
present, with model guidance suggesting an increase in mid level
moisture by Monday. This increase will be due in part to an area of
more humid air filtering into the region, related to a weak wave
moving south of the islands by late Sunday and into Monday and
generally southeast wind flow bringing more humidity from lower
latitudes. This area of more humid air will have PWAT values between
1.5 and 1.9 inches. This moisture will persists through the rest of
the long term forecast period. Generally speaking, shower activity
will affect windward sectors of the islands during overnight and
morning hours. During afternoon hours, diurnal and local effects
will promote convective activity mainly over interior to
western/northwestern Puerto Rico, with showers possibly
developing west/northwest of El Yunque and the local islands.
Variations in this pattern will depend in part on available
moisture, with days with more moisture having more shower
activity.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, SHRA developing over
the western interior may cause BKN/OVC cigs at FL035-FL060 at TJBQ
btw 17z-23z. Sfc winds ESE at 8-12 kt with sea breeze variations aft
14z. Light and variable winds expected around 22z and through the
night.

&&

.MARINE...Generally southeast winds and a northeasterly swell
will promote seas between 3 and 5 feet, occasionally 6 feet,
particularly across northern waters and the Mona Passage. Pulses
of weak long dominant period northeasterly swells will continue to
affect the local Atlantic waters the remainder of the workweek.
Passing showers will affect the coastal waters especially during
the afternoon and overnight hours. A moderate risk of rip currents
is expected today for northern beaches of Puerto Rico from Rincon
to Ceiba, as well as for beaches of Vieques, Culebra and the
USVI.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 11 AM this morning to 5 PM AST this afternoon
for PRZ001-002-005-008.

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

$$

SHORT TERM...DS
LONG TERM....MRR

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
507 AM AST Wed May 3 2023

.SYNOPSIS...Overall stable conditions are expected today and
tomorrow before local effects promote afternoon convection mainly
over interior and western Puerto Rico. Southeasterly winds and
somewhat drier conditions will promote heat indices between
102-107 degrees across lower elevations of northern and western
Puerto Rico today. An increase in moisture and instability is
expected for Friday before drier air with additional dust
particles filters in during the weekend.

&&

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

A weak surface high pressure over the central Atlantic and a
developing low over the northwestern Atlantic will continue to
promote east to southeasterly trades across the northeastern
Caribbean through the short term period. Small surges of low level
moisture and areas of drier air embedded in this flow will reach the
local area at times from the Tropical Atlantic. The precipitable
water content will remain below normal in general across the region
during the next couple of days. Therefore, showers will form due to
local effects during the afternoons and mainly over the northwest
quadrant of PR. Across the USVI and the eastern half of PR, limited
rainfall activity is expected as the area remains under the
influence of mid and upper level ridges. However, a short wave
trough is expected to move over the region by Friday, while a pre-
frontal trough develops over or just north of Hispaniola and pulls
better moisture content from the Caribbean waters across the
islands. As moisture and instability increases on Friday, the areal
coverage of showers will also increase over the islands, and an
isolated thunderstorm cannot be ruled out with the afternoon
convection over PR.

Under sunny skies, southeasterly trades, and somewhat drier
conditions the heat index will remain between 102-107 degrees in
general across the lower elevations of northern and western Puerto
Rico through Thursday. However, a Heat Advisory may be required once
again on Friday as humidity increases along the northern coastal
municipalities of PR.

&&

.LONG TERM...Saturday through Thursday...

No major changes to the long term forecast. A surface high
pressure system will promote generally southeast winds for most of
the period. A drier air mass (including Saharan Dust
particulates) with some patches of moisture is expected to filter
into the region through most of the weekend. Moisture that moved
across the islands to end the short term period and from a more
recent frontal boundary will be north of the islands. Warmer
temperatures and heat indices across the islands will also be
experienced due to the southeasterly winds, particularly across
northern Puerto Rico. Dry mid levels will be present, with model
guidance only suggesting an increase in mid level moisture by late
Monday into Thursday night. This increase will be due in part to
more humid air filtering into the islands, related to a weak wave
moving south of the region by late Sunday and into Monday and
generally southeast wind flow bringing more humidity from lower
latitudes. This area of more humid air will have PWAT values
between 1.5 and 1.9 inches. This moisture will persist through the
rest of the period, diminishing somewhat on Thursday. The typical
diurnal pattern with generally southeast winds is expected, with
showers varying in coverage and intensity in part by how much
moisture is available. Shower activity will generally affect
windward sectors of the islands during overnight and morning
hours. During afternoon hours, diurnal and local effects will
promote convective activity mainly over interior to
western/northwestern Puerto Rico, with posible shower development
also west/northwest of El Yunque and the local islands.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, SHRA developing over
western PR may cause tempo MVFR conds at TJBQ btw 18z-22z. East to
southeast winds will increase between 8 and 14 kts with sea breeze
variations after 14z.

&&

.MARINE...Generally southeast winds and a northeasterly swell
will promote seas up to 6 feet across the northern offshore
Atlantic Waters, where small craft should exercise caution. Pulses
of a weak mid to long-dominant period northeasterly swell will
continue to arrive across the local Atlantic waters throughout the
workweek. A high risk of rip currents is expected today for
northern beaches of Puerto Rico from Rincon to Fajardo, as well as
for beaches of Culebra and the easternmost beaches of St. Croix.
A moderate risk is also expected for Vieques, the northern USVI,
Rincon and Ceiba.

&&

.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 VIZ002.

AM...None.
&&

$$

SHORT TERM...DS
LONG TERM....MRR

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
456 AM AST Thu May 4 2023

.SYNOPSIS...A limited to elevated risk of excessive heat will
continue mainly across the lower elevations of northern Puerto
Rico during the next couple of days. An upper level trough will
increase instability on Friday, and another one by early next
week. A weak Saharan Air Layer could cause hazy skies during the
weekend. Normal to above normal moisture content is forecast for
next week.


&&

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

The wettest day of the short-term period will likely be Friday,
while today is likely to be the driest. Warm conditions will also
continue, with heat indices in excess of 102F for many coastal
areas.

Relatively dry air is in place over the region today, though patchy
moisture is being carried into the area from time to time. The 0Z
sounding showed precipitable water at 1.40 inches, which is below
seasonally typical values. Total Precipitable Water imagery from
GOES-16 shows that there is a sizable patch of moisture south of
the region, but it is not likely to reach the islands until this
evening. There is also ridging aloft, providing stability. As such,
limited shower activity is expected today. Still, local effects and
daytime heating will bring some showers to interior and western into
northwestern Puerto Rico this afternoon. Streamer activity in the
east cannot be ruled out, but is not likely to result in much, if
any, rainfall.

Increased rainfall is expected tonight as the patch of moisture
reaches the islands from over the Caribbean. This patch will
dissipate slightly through the day on Friday, but linger over the
region. Additionally, a weak deep-layer trough will shift to just
west/northwest of the region, resulting in a modest increase in
instability. As such, an increase in shower activity is expected.
Isolated showers are also possible. This trough is forecast to move
over the islands and then away from the region to the east early on
Saturday. This will lead to a decrease in instability. However, a
frontal boundary well north of the area will result in some moisture
convergence, mostly north of the islands, but it could coincide with
the typical daily convergence due to sea breezes over northwestern
and interior Puerto Rico. Because of this, the decrease in shower
activity may be slightly inhibited.

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

A weak Saharan Air Layer (SAL) is expected to move early in the
long term period over the region. This will promote somewhat hazy
skies and drier mid-level air, particularly on Sunday. However,
an upper level trough and a pre-frontal trough just north of the
area will aid in the development of afternoon convection over
western PR from Monday and onwards, as precipitable water content
increases to above normal content through at least midweek.
Therefore, a seasonable weather pattern is expected with
measurable rainfall across the USVI during the night/early morning
hours, followed by better organized afternoon shower activity
over portions of the northwest quadrant of PR, and across San Juan
and vicinity from showers developing off el Yunque region.
Another pre-frontal trough is forecast to develop by the end of
the workweek to our northwest, promoting a similar weather
pattern.


&&

.AVIATION...Generally VFR conds expected for all aerodromes next 24 hrs.
Afternoon convection likely over interior into W/NW PR. SHRA are
possible near TJBQ, though impacts to terminal are likely to be
limited, if any. Passing SHRA expected tonight, particularly over
Caribbean, pushing onshore at times. Highest potential for impacts
tonight for TISX/TIST/TJPS.


&&

.MARINE...Small pulses of a long period northeasterly swell will
continue through the end of the workweek. This, in combination
with a northeasterly sea breeze across the Atlantic waters should
maintain an elevated risk of rip currents for most beaches with a
northern exposure of PR, and occasionally across the eastern coast
of St. Croix. Another small swell, from the northwest will keep
the risk elevated into Saturday. Seas in general will range
between 2 and 5 feet, with the highest seas expected across the
northern waters and passages. Light to moderate east to southeast
trades will prevail for the next several days.


&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through late tonight for Prz001-002-005-
008-012.

VI...High Rip Current Risk through this afternoon for VIZ002.

AM...None.
&&

$$

SHORT TERM...CS
LONG TERM....DS

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
426 AM AST Fri May 5 2023

.SYNOPSIS...Hot temperatures and higher dewpoints than previous
days will cause heat indices to range from 108-112 degrees
Fahrenheit across portions of northern and western Puerto Rico
today. Therefore, an Excessive Heat Warning and a Heat Advisory
were issued. A weak Saharan Air Layer will cause hazy skies during
the weekend and the following week. Normal to above normal
moisture content is forecast for next week with increased shower
activity.


&&

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

Today's main concern is once again excessive heat. Generally
southeasterly winds due to a surface high pressure system and
available moisture will continue to produce elevated heat indices.
Heat index values possibly reaching up to 112 degrees will be
experienced across lower elevations of northern Puerto Rico today,
with most lower elevations also being around 100 degrees. High
temperatures will continue to be experienced through the short term
forecast period. Take extra precautions, if planning to work or
spend time outside.

Today will be the wettest day of the short term period. Satellite
derived Precipitable Water (PWAT) show a more humid air mass over
our region with values up to around 1.7 inches. Model guidance
suggest another patch of moist air, currently southeast of the
region, moving towards the islands. PWAT values could increase to
around 1.9 inches. An upper trough will be affecting the region by
the weekend. However, by late tonight and into Saturday a drier air
mass, with PWAT values of around an inch, and a weak Saharan Air
Layer (SAL) will filter into the forecast area, promoting drier
conditions. This will promote somewhat hazy skies, particularly on
Sunday. Model guidance suggests an increase in moisture by Sunday.
Moisture that moved across the islands and from a recent frontal
boundary will remain north of the islands Saturday and Sunday.

The typical diurnal pattern with generally southeast winds is
expected, with showers varying in coverage and intensity in response
to available moisture. Most of the available moisture however will
be in the lower levels as ridging and drier air aloft will persist
and serve to limit shower development. During the overnight and
morning hours, shower activity will affect windward sectors of the
islands. During the afternoon, diurnal and local effects will
promote shower activity mainly over interior to western/northwestern
Puerto Rico, with shower development also possible west/northwest of
El Yunque and the local islands.

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

A weak Saharan Air Layer (SAL) will prevail over the region
through much of the long term period. This will promote somewhat
hazy skies and drier mid-level air intrusion. However, an upper
level trough and a pre-frontal trough just north of the area will
aid in the development of afternoon convection over western PR on
Monday and Tuesday, with a slight possibility of thunderstorms. A
drier air mass will generally dominate the area on Wednesday and
Thursday, with the best moisture converging over western PR in the
afternoon hours. Then, on Friday into the weekend, another pre-
frontal trough is forecast to develop just west and north of the
area, promoting instability and increasing showers once again in
general across the islands.


&&

.AVIATION...Mainly VFR conditions will continue across the terminals,
brief MVFR conditions possible due for TJBQ during the afternoon
hours as convection develops. Wind flow will be generally from the
SE up to around 12 kts, with higher gusts and sea breeze variations.
A weak Saharan Air Layer (SAL) will approach the area late tonight
into Saturday.


&&

.MARINE...A 3 ft long period northerly swell will continue to
move across the Atlantic waters and portions of the local passages
during the next day or so. This, in combination with the sea
breeze across the Atlantic waters should maintain an elevated risk
of rip currents for most beaches with a northern exposure of PR,
and occasionally across the eastern coast of St. Croix. Seas in
general will range between 2 and 5 feet, with the highest seas
expected across the northern waters and passages. Southeast
trades up to 15 kt will prevail through the weekend.


&&

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

Heat Advisory from 11 AM this morning to 5 PM AST this afternoon
for PRZ001-008-010.

Excessive Heat Warning from 11 AM this morning to 5 PM AST this
afternoon for PRZ005.

VI...High Rip Current Risk through this afternoon for VIZ002.

AM...None.
&&

$$

SHORT TERM...MRR
LONG TERM....DSR

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
502 AM AST Sat May 6 2023

.SYNOPSIS...
An increase of Saharan Dust across the region will cause hazy
skies today. This drier air will limit shower activity mainly to
afternoon convection. Hot afternoons are expected to occur over
the next few days. Monday into Tuesday an increase of showers is
expected. The risk of rip currents is moderate to low this
weekend.

&&

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

Today, Puerto Rico and the U.S. Virgin Islands will experience a mix
of sunshine and clouds due to a dry air mass moving from the east.
This air mass will also cause relatively hazy skies as African dust
particles are brought in. The east-southeast winds will persist,
resulting in warm temperatures, particularly in the urban areas of
northern Puerto Rico and St Croix. Heat indices are expected to
range between 102 and 107 degrees Fahrenheit from 10 am to 4 pm
today. The east-southeasterly winds will cause some rain showers
along the southeast coast and in the surrounding waters of St Croix
around mid-morning. As the day progresses, sea breeze variations,
diurnal heating, and local factors will lead to afternoon convection
in the northwest area of PR and downwind from the USVI.

A broad mid to upper-level trough will pass through the area this
weekend, moving toward the Atlantic by Monday afternoon.
Unfortunately, there will not be much rain due to a lack of
moisture. Moreover, African dust particles will remain present in
Puerto Rico and the U.S. Virgin Islands through the weekend and next
week. The warm spell will likely continue Sunday.

Around Monday, a weak easterly wave might bring additional moisture
to the Northeast Caribbean. This wave could result in favorable
rainfall for Puerto Rico and the U.S. Virgin Islands and a slight
cooling effect.


&&

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

An upper level trough north of the region will enhance afternoon
convection on Tuesday, mainly across western Puerto rico. A Saharan
Air Layer is expected to thicken on Wednesday, promoting hazy skies
and drier conditions. A typical weather pattern will prevail each
day with a chance of passing showers each morning followed by an
increase of clouds and showers during the afternoon hours. However
during the afternoons, thunderstorms remain a possibility. East
to southeasterly flow is expected throughout this time, resulting
in warm days especially across coastal urban areas. Moist air
starts to reach the region on Saturday, which will increase shower
activity over next weekend.

&&

.AVIATION...Mainly VFR conditions expected for the forecast
period. Hazy skies may result around mid-morning, but visibilities
will remain P6SM. SHRA will develop across NW-PR between
06/18-22z and may impact JBQ, but impacts to operations are
expected to be minimal. Winds will continue calm to light/VRB,
returning from the ESE at 10-15 kt aft 06/13z.

&&

.MARINE...East to southeast winds with light to moderate speeds
will prevail into the weekend. Weak northerly swell will remain
across the Atlantic waters and passages for the next few days.
Together these are generating seas up to 4 feet. Winds will begin
to strengthen on Sunday. The risk of rip currents is moderate
across northern facing beaches as breaking waves are generally 5
feet. Southern Puerto Rico has a low risk.


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

$$

RC/CAM

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
439 AM AST Sun May 7 2023


.SYNOPSIS...
Hot days with somewhat hazy skies are expected over the next day
or two. An increase of showers is forecast for Monday night into
Tuesday. On Wednesday a thicker plume of Saharan dust will
arrive. Next weekend an increase of rain is forecast. There is a
moderate to low risk of rip currents for the next several days.

&&

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

The islands will continue to experience warm weather, with the heat
index reaching the mid-100s Fahrenheit in urban and coastal areas of
Puerto Rico. The skies will be sunny but somewhat hazy due to dust
particles from the African Deserts. Wind will come from the east-
southeast, and there may be a chance of one or two brief rain
showers passing through the U.S. Virgin Islands and eastern Puerto
Rico in the morning. Maximum temperatures will reach the upper 80s
and low 90s, mainly along the coastal sections.

A broad mid to upper-level trough moving through the Northeast
Caribbean will increase somewhat local instability. While there may
be limited rainfall due to low moisture levels, sea breezes, diurnal
heating, and local factors will likely cause afternoon convection in
the northwest quadrant of Puerto Rico as the day progresses.

The warm weather might stick around on Monday and Tuesday, but
there's a chance of rain in the afternoon and evening due to a weak
easterly wave interacting with the mid to upper-level trough. These
weather features could be good news for Puerto Rico and the U.S.
Virgin Islands, as they could bring much-needed rainfall and cooler
temperatures.

&&

.LONG TERM...Wednesday through Sunday...
A surface high stretched across the eastern Atlantic will continue
an east-southeasterly flow across the region during this time.
Wednesday seems to be the haziest day of the week as a plume of
Saharan Dust arrives. The weather will be a consistent pattern of
passing showers followed by afternoon convection driven by
diurnal heating and local effects. Each day precipitable water
values range around normal seasonal values, which will support
good rainfall across western Puerto Rico each afternoon. A moist
airmass arrives to the region Friday night and last into the
weekend. During this time a wetter pattern is forecast compared to
the previous days.

&&

.AVIATION...Mainly VFR conditions expected to prevail across all
terminals for the forecast period. SHRA will develop across NW-PR
btwn 07/18-22z and may impact TJBQ (without significant impacts to
operations). HZ due to Saharan dust will continue, but with VIS at
P6SM. Winds will continue calm to light/vrb, returning from the ESE
at 10-15 kts, with sea breeze variations aft 07/13z.

&&

.MARINE...Southeasterly to easterly winds of up to around 10 to
15 knots will continue across the local waters. Pulses of small
northerly swell will affect the local waters over the next few
days. Still, seas of 4 feet or less are expected today until
tonight when seas raise up to 5 feet.

There is a moderate risk of rip currents for beaches of the USVI,
Culebra, and northern Puerto Rico and this should continue
through at least midweek

&&

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

$$

RC/CAM

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
436 AM AST Mon May 8 2023

.SYNOPSIS...
A showery pattern will begin today and will continue into
tomorrow. Hazy skies due to suspended dust particles will prevail
throughout the week, especially on Wednesday. A wetter pattern
will arrive next weekend due to moist air moving into the region.
The risk of rip currents remains moderate for northern and eastern
facing beaches, and is low elsewhere.

&&

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

Traces of suspended dust particles will be present in the region for
a while. There will be a showery pattern today and tomorrow caused
by a surface disturbance from the east and a trough in the mid to
upper levels. As a result, we can expect rain showers to occur more
frequently throughout the day. Passing showers will likely happen
across the local waters, U.S. Virgin Islands, and eastern Puerto
Rico in the morning, followed by showers developing across the
interior and western sections of Puerto Rico in the afternoon. Some
haziness will be present in the region without rain activity, and
temperatures are expected to stay above normal. Isolated
thunderstorms due to local effects, excessive diurnal heating, and
sea breeze cannot be ruled out each afternoon. A further increase
in moisture will happen on Tuesday, which may lead to the wettest
day.

By Wednesday, the winds are expected to shift towards the south-
southeast, which could prolong the warm spell due to above-normal
temperatures across the islands. Also, some model guidance suggests
an increase in suspended dust particles, which may cause hazy skies.
Despite this, patches of moisture carried by the winds and the
effects of the sea breezes may result in typical rain activity.

&&

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

A mid to upper-level trough north of the region will maintain a
seasonal pattern of passing showers during the morning hours
followed by afternoon convection mainly across western Puerto
Rico. A wetter pattern is forecast for long term as moist air is
expected to arrive on Friday, lasting through the following
several days. As a result, more rainfall is forecast for this time
with Saturday afternoon looking to be the standout for the
weekend, then precipitable water values rise again to wet values
on Monday. During these days there is a chance for flooding across
areas with the heaviest rainfall, mostly for the interior to
western sections of Puerto Rico. East- southeasterly surface wind flow
will prevail during this time, resulting in warm afternoons
mainly across urban coastal areas.

&&

.AVIATION...Mainly VFR conditions with hazy skies due to
suspended Saharan dust will prevail thru the forecast period (but
with VIS remaining at P6SM). SHRA will increase somewhat due to an
easterly perturbation, and it may result in afternoon TSRA across
the interior and NW-PR btwn 08/18-22z. Expect calm to light-VRB
winds thru 08/13. After 8/13z, the winds will return from the ESE
at 13-17 knots with occasional strong gusts and sea breeze
variations.

&&

.MARINE...

A weak northerly swell will fill in to the local waters today.
Moderate to locally fresh east to east-southeast winds are
possible throughout the day, causing some choppy conditions
across the waters. Seas will remain generally 5 feet or less.

There is a moderate risk of rip currents for most northern and
eastern exposed beaches. The risk is low for southern facing
coastlines.

&&

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

&&

$$

RC/CAM

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
443 AM AST Tue May 9 2023

.SYNOPSIS...
Occasional passing showers across the eastern half of region
followed by afternoon storms across western sections of Puerto
Rico will prevail over the next several days. Hot conditions are
expected across coastal areas today, especially for urban areas.
Therefore, a Heat Advisory is in effect today for north-central
Puerto Rico. An increase of dust particles is expected on
Wednesday, causing hazy skies. The risk of rip currents remains
moderate to low for the next several days.


&&


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

The lingering moisture of yesterday's perturbation and the remnants
of an old frontal boundary north of the region will promote
occasional passing showers across the eastern half of Puerto Rico
and the U.S. Virgin Islands throughout the day. The islands will
experience periods of sunshine.

A jet aloft, local effects, excessive heating, and sea breeze
variations will result in another round of moderate to locally heavy
rain and isolated thunderstorms across the northwest quadrant of PR
and downwind from El Yunque during the afternoon. Periods of heavy
rains may result in urban and small stream flooding across the
northeast and northwest Puerto Rico.

Winds continue from the east-southeast, and temperatures will remain
higher than usual, particularly in urban and coastal regions. Due to
the combination of moisture and air temperature, heat indices will
reach the mid-100s. Additionally, a Heat Advisory has been issued
for North-Central Puerto Rico due to heat indices ranging from 108-
111 degrees Fahrenheit during mid-morning and afternoon hours.

The winds will continue from the south-southeast on Wednesday,
prolonging the warm spell due to above-normal temperatures across
the islands. Also, some model guidance suggests an increase in
suspended dust particles, which may cause hazy skies. Despite this,
patches of moisture carried by the winds and the effects of the sea
breezes may result in typical rain activity. On Thursday, the
weather pattern for the season will continue. However, winds from
the east will cause afternoon convection to develop along and to the
west of the Cordillera Central.




&&

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

An upper level low in the Gulf of Mexico and a trough in the mid
Atlantic will promote at times strong westerly flow aloft during
this long term period. This should maintain good ventilation
aloft which will aid in the development of afternoon thunderstorms
across interior to western Puerto Rico, especially northwestern
Puerto Rico as lower level wind flow will assume an easterly to
southeasterly flow. The main driver of active weather will be the
amount of moisture available, which it looks to be that Saturday,
Monday, and Tuesday night will have the highest precipitable water
values. However, the air that is moving in is quite patchy in
moisture content so no wide spread rainfall is expected during
this time. During these standout days, flooding is possible
across the areas that receive the highest amounts of rainfall.
Warm temperatures with heat indices in the 100s will continue
across coastal regions of the local islands as this east-southeast
surface flow prevails.


&&

.AVIATION...VFR conditions will prevail through much of the fcst
period. SHRA will move across IST/ISX/JSJ throughout the day.
Skies will continue to be hazy with P6SM visibilities. Afternoon
SHRA/TSRA will develop across NW-PR, impacting JBQ and creating
MVFR or brief IFR conditions (btwn 9/18-22z). Expect calm to light
and variable winds through 9/13z, when they will return from the
ESE at 15-20 knots with higher gusts and sea breeze variations.


&&

.MARINE...Moderate to locally fresh east to east-southeasterly
winds will persist across the regional waters as a surface high
pressure remains in place across the eastern Atlantic. Weak
northerly swell will continue to arrive for the next few days.
Together these are resulting in seas up to 5 feet across most of
the local waters.

There is a moderate risk of rip currents for beaches of the northern
USVI, Vieques, Culebra, and north-facing beaches of Puerto Rico.
The risk is low elsewhere.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 11 AM this morning to 4 PM AST this afternoon
for PRZ005.

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

&&

$$

RC/CAM

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
424 AM AST Fri May 12 2023

.SYNOPSIS...

Patchy moisture will continue to affect the region into next week,
with generally increasing moisture. Moisture convergence is expected
during the workweek next week, resulting in more active weather.
Seas will remain generally less than 5 feet into this weekend.

&&

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

The main hazards throughout the short term forecast period are the
elevated risk of heat, mainly for northern and western Puerto Rico,
as well as urban and small stream flooding each afternoon along the
interior and western Puerto Rico. A surface high pressure over the
eastern Atlantic will maintain the trade winds well established from
the east to east southeast a little faster than previous days,
reaching 10 to 15 knots at the low levels. Just northwest of the
area, there is a weak front dissipating. A patch of moisture will
move in today over the islands, with precipitable water values
reaching 1.5 inches. Additional patches of moisture will be induced
in the trade winds east of the Leeward Islands and move closer by
the weekend. As a result, the frequency of showers will increase
through Sunday, with a typical pattern of passing activity moving
across eastern Puerto Rico and across the Virgin Islands throughout
the day, and convection developing in the interior and west each
afternoon. Isolated thunderstorms are also expected each afternoon
across the interior and west. On Sunday, an upper level low near
Florida and an upper level ridge centered east of Venezuela will
cause southerly winds at these levels. Moisture will be dragged
aloft, resulting in some high clouds.

&&

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

Moisture will continue to increase on Monday. With the steering flow
becoming weaker over the region, as the surface ridge over the
Atlantic weakens and shifts eastward, moisture convergence is
anticipated across the area, likely lasting at least into Wednesday.
Late Wednesday into the end of the weak, the ridge restrengthens,
pushing westward, leading to an increase in winds again. Because of
this, the moisture is likely to get slightly more patchy for the
second half of the week. Moisture levels will be on the high end of
normal or just above normal for Tuesday and Wednesday, remaining
within seasonal normals through the end of the workweek.

Aloft, a mid- to upper-level ridge will be in place over the region
through much of the week. On Tuesday, an upper-level low will pass
by the area to the northwest as it weakens. An upper-level jet will
also be in place over the area on Tuesday, and possibly into
Wednesday as well. The best instability over the region is likely to
be Tuesday, with somewhat less for Wednesday.

The wettest days of the period are likely to be Tuesday and
Wednesday, but active weather is anticipated through the period.
Increasingly southerly winds over the region in the low levels will
likely result in another period of warmer temperatures. Combined
with the high humidity, there is the potential for excessively high
heat indices around midweek next week.

&&

.AVIATION...
(06Z TAFS)

Mainly VFR conditions expected. SHRA and TSRA are expected to
develop after 17Z across the interior and western Puerto Rico,
resulting in mountain obscuration. FL050 winds will be out of the SE
at 12 to 17 knots, diminishing after 22Z over land.

&&

.MARINE...

Winds of around 12 to 18 knots are expected out of the east to east-
southeast over the region, with locally stronger winds, particularly
near the northern and southern coasts of Puerto Rico, to around 20
knots. This will sustain some choppy conditions across the waters.
Seas will remain around 4 feet or less across the waters.

There is a low risk of rip currents for the local beaches.

&&

.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
350 AM AST Sat May 13 2023


.SYNOPSIS...
Typical conditions will persist throughout the weekend, with
showers developing each afternoon across the interior and western
of Puerto Rico, while additional activity moves at times across
the east and over the U.S. Virgin Islands. Moisture will increase
throughout the next workweek, enhancing the potential for urban
and small stream flooding. Heat indices will remain elevated,
especially for the late morning and afternoon hours across
coastal and urban areas, and across the valleys.


&&

.SHORT TERM...
Current forecast trends suggest that a typical shower pattern will
be maintained over the region through the short-term period. Less
activity than yesterday is expected today, and today looks like it
will likely be the wettest day of the three. Cannot entirely rule
out a wetter day for Monday, though.

Moisture persists over the region today, particularly for the
northern portions of the area, including the Atlantic waters and
parts of the islands. Precipitable water values over the region are
on the high end of seasonally typical, based on the 0Z sounding and
Total Precipitable Water imagery from GOES-16. There is somewhat
drier air over the south, though moisture levels remain within
seasonal normals, which will push over the islands during the day
today. Because of this, typical shower activity is expected for the
region, though the afternoon will likely be less active today than
it was yesterday.

Patchy moisture will continue to stream over the region in the
southeasterly flow tomorrow. Overall, though, moisture will decrease
over the area, to the lower end of climatological normals. This will
still support shower activity, however, though likely somewhat less
than today.

On Monday, moisture will begin to increase over the area. The
steering flow will slow somewhat, resulting in moisture convergence
over the area. Meanwhile, a jet is forecast to be over the region at
the upper-levels, providing some ventilation aloft. There is some
uncertainty considering the location of the moisture by the
afternoon, with a dry patch in the vicinity of the islands, and
possibly over western portions of the region, including parts of
Puerto Rico. Depending on timing and exact locations of moisture,
the forecast could vary quite substantially for some areas,
particularly in northwestern and interior portions of Puerto Rico.
Current model guidance suggests that the dry slot will inhibit
shower activity for northwestern and interior Puerto Rico, but it is
likely that at least some shower and thunderstorm activity will
occur. Cannot entirely rule out the potential for some strong
showers and/or thunderstorms developing later in the afternoon. A
small shift in the moisture pattern will have significant impacts
for Monday.

&&

.LONG TERM...Tuesday through Sunday...
A surface to mid level high pressure over the eastern Atlantic
will maintain the wind flow out of the southeast to south on
Tuesday and Wednesday, from the east by the end of the workweek,
and again from the southeast during the weekend. The high will
weaken in response to a mid to upper trough northwest of the
islands. The reflection of this trough at the surface will cause
moisture convergence from the induced patches of moisture reaching
the islands from the east. This will cause moisture levels to
remain above seasonal levels throughout most of the week. Aloft,
instability will be enhanced by the trough and a jet stream
crossing the region. All these ingredients will result in an
increase in showers and thunderstorms across the islands. The risk
for urban and small stream, mudslides in areas of steep terrain,
as well as water surges along rivers will be elevated throughout
this period. The focus of rain will vary depending on the wind
direction, but the interior, western and northern sections of
Puerto Rico should receive the highest amounts of rainfall each
afternoon, while eastern Puerto Rico and the U.S. Virgin Islands
will receive passing shower activity throughout the day and
night. If there is enough sunshine during the daytime,
temperatures will climb up into the upper 80s and low 90s. With
all the available moisture at the low levels, it will feel very
uncomfortable with heat indices surpassing 102 degrees.

&&

.AVIATION...
Generally VFR conds expected over next 24 hrs. Passing SHRA over
waters continue into morning, with limited impacts expected for
TIST/TISX/TJSJ/TJPS. Afternoon convection will bring SHRA/TSRA to
interior into NW PR. Streamer activity possible in the east,
including the San Juan streamer. Brief MVFR or worse cannot be ruled
out for TJBQ/TJSJ.

&&

.MARINE...
Marine conditions will remain tranquil, with seas below 2 to 4
feet. However, isolated thunderstorms are expected each afternoon
near the coastal areas of western Puerto Rico. Seas could be
locally hazardous around thunderstorms. Winds will be from the
southeast at 10 to 15 knots, with higher gusts near thunderstorms.

&&

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

$$

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
430 AM AST Sun May 14 2023

.SYNOPSIS...Showers and thunderstorms are expected to develop
across western areas of Puerto Rico as well as portions of the
San Juan metro area this afternoon. A similar weather pattern is
expected to prevail much of the upcoming workweek due to available
moisture, diurnal heating and local effects. The risk for urban
and small stream flooding, heat indices in the upper 90 degrees
to the low 100s, and low to moderate risk of rip currents
continues.

&&

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

The overall pattern is for today to be slightly less active than
yesterday, followed by an overall drier day tomorrow. The wettest
day of the short term period is likely to be Tuesday.

Patchy moisture is pushing into the region from the east and
southeast this morning. Precipitable water values will remain
generally within seasonally typical values over the region. This
will help to sustain a typical shower pattern, overall. The steering
flow is generally southeasterly, though there is quite a bit of
shear above around 700 hPa, with winds becoming more southerly then
west-southwesterly. This could result in showers being over some of
north central Puerto Rico again today, though overall the pattern
indicates that the peak in activity will be over northwestern and
interior Puerto Rico. Streamer development is also likely in the
east again today.

Tomorrow, a dry slot is expected to move over part of the region,
including southern and western portions. This will inhibit,
somewhat, the shower activity over the region. However, moisture
levels are likely to only dip to around the lower end of normal, so
some shower activity is still likely. Additionally, an upper-level
jet is expected to be over the region on Monday, resulting in a
modest increase in instability. Because of this, Monday is still
likely to see active weather, though it could be the driest day of
the period.

For Tuesday, moisture will increase. The overall steering flow will
be slower than previous days, as the high pressure over the central
Atlantic will weaken and be pushed eastward by an approaching
surface trough. This will result in moisture convergence over the
islands through the day on Tuesday. Model guidance is more bullish
on an upper-level trough that is expected to pass by the region to
the northwest than it has been in previous days. Because of this,
there is less certainty in the forecast, but this does suggest the
potential for some troughing at around 250 hPa just west of the
islands on Tuesday. If this does verify, Tuesday would also bring an
increase in instability alongside the increase in moisture. Because
of this, it is likely that Tuesday will bring enhanced shower
activity. The steering flow is also forecast to become a bit more
southerly overall through the afternoon, which could push the peak
in shower activity eastward to over most of northern Puerto Rico.


&&

.LONG TERM...Wednesday through Monday...

A mid to upper level ridge pattern is expected to prevail across
the forecast area Thu-Fri, as the aforementioned trofiness at
around 250 hPa dissipates north of the forecast area early in the
cycle. Nevertheless, the ridge pattern aloft will be short-lived
with the 250 hPa heights falling once again Saturday into the rest
of the upcoming weekend. At lower levels, a surface high pressure
located across the northeast Atlantic will continue to yield east
to east southeast winds. This will promote moisture advection and
precipitable water values near or above seasonal levels much of
the week.

Under this evolving pattern, locally induced afternoon showers and
thunderstorms are expected across western areas of Puerto Rico each
day. The risk for urban and small stream flooding, mudslides in
areas of steep terrain, as well as water surges along rivers will
be elevated. Daytime temperatures across Puerto Rico and the U.S.
Virgin Islands will remain in the mid to upper 80s and low 90s
along the coastal areas and in the mid 80s across the central
portions. Heat indices will stay in the upper 90 degrees to the
low 100s along the coastal areas of the islands.

Based on the latest guidance, the wettest day in the long term
forecast is likely to be Wednesday.

&&

.AVIATION...Generally VFR conds expected next 24 hours for most
aerodromes. Passing SHRA cont over the waters thru morning; SHRA
near TIST/TISX/TJSJ likely to have little to no operational
impacts at terminals. Afternoon SHRA/TSRA expected for interior
and W/NW/N PR. Streamer dvlpmnt off of terrain likely in E, incl
San Juan streamer. Greatest risk of impacts is for TJBQ, followed
by TJSJ; cannot rule out brief MVFR or worse, esp for TJBQ.
Passing SHRA return tonight.

&&

.MARINE...Mariners should expect seas between 3 to 5 feet, with
occasional seas up to 6 feet. Showers with isolated thunderstorms
are expected each afternoon at the coastal areas of western and
northwestern Puerto Rico. Choppy seas could be locally hazardous
in and around thunderstorms. Winds will be from the SE at 10 to 15
knots, with higher gusts near thunderstorms. There is a moderate
risk of rip currents along the north and east facing beaches of
Puerto Rico and Culebra.

&&

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

$$

SHORT TERM...CRS
LONG TERM....OM
AVIATION...CRS