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989
FXCA62 TJSJ 201745
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
145 PM AST Mon Apr 20 2026

...New SHORT TERM, AVIATION, MARINE, BEACH FORECAST...

.KEY MESSAGES...
Updated at 145 PM AST Mon Apr 20 2026

* Mostly sunny skies prevailed across the Virgin Islands. Fair
  weather, with a few passing showers possible, are expected to
  persist through the next couple of days.

* Drier weather is expected for much of Puerto Rico, but afternoon
  showers will continue to develop along the interior and west each
  afternoon.

* A moderate rip current risk is expected through midweek, mostly
  for north and east Puerto Rico and for the Virgin Islands.

&&

.Short Term(This evening through Wednesday)...
Issued at 145 PM AST Mon Apr 20 2026

After a cool to mild morning across Puerto Rico, temperatures warmed
up to the mid and upper 80s along many coastal areas, and into the
upper 70s in the highest mountains. Winds were mostly from the east
at 10 to 15 mph. Skies were sunny to partly cloudy with only a few
showers moving over portions of eastern Puerto Rico at times.
Afternoon showers are expected again along the interior and west,
but rain activity is not expected to be as widespread and long-
lasting as in the previous days.

Conditions are expected to be less wet than last week, as a mid
level mid ridge builds west of the islands. This will cause dew
point depressions to increase to about 10 to 20 degree Celsius,
which translate into a much more manageable weather pattern across
the local islands. As is usual, the trade winds will drag some
irregular low level patches of moisture that bring isolated to
scattered showers across portions of Puerto Rico and the Virgin
Islands. Also, diurnal heating should be enough to generate showers
along the interior and west of Puerto Rico. Since some streams are
still running high, minor urban and stream flooding can be
anticipated, and roads that are already flood might take longer to
finally drain.

On Tuesday, as a polar trough drives a cold front just north of the
area, the winds are expected to gain a northerly component at the
low and mid levels of the atmosphere and will become weaker as well.
Not a lot of rain is expected over land associated with this
feature, but temperatures will remain near normal for this time of
year, with highs in the mid-80s for coastal areas, and below 80 in
the mountain. At night, temperatures will cool down to the mid-60s
in the mountain, and the mid-70s for coastal areas.

&&

.Long Term(Thursday through Monday)...
Issued at 155 AM AST Mon Apr 20 2026

A seasonal weather pattern is expected to prevail at the start of
the long-term period, with precipitable water values near
climatological normals and typical trade wind showers moving across
the local waters and windward sectors during the overnight and
morning hours. Afternoon convective development will remain possible
across interior and western portions of Puerto Rico, aided by
daytime heating, local effects, and sea breeze convergence. While
widespread rainfall risk is not anticipated early in the period,
moderate rainfall may still cause localized ponding in urban and
poorly drained areas, especially where showers persist or repeatedly
affect the same locations.

By late Thursday into Friday, a gradual increase in available
moisture is expected as the remnants of a frontal boundary linger
north of the region while low-level winds become more southerly.
This evolving pattern will promote warmer temperatures and a more
humid air mass across the islands. As a result, shower coverage
should become more numerous, with the greatest afternoon activity
focused over interior and northern to northwestern Puerto Rico,
although passing showers will remain possible elsewhere. Localized
urban and small stream flooding will become more likely where
stronger showers develop.

From Saturday through Monday, southeasterly to southerly flow is
forecast to persist and continue transporting tropical moisture into
the northeastern Caribbean. Precipitable water values are expected
to rise to above normal levels, supporting a wetter and more
unstable pattern. Combined with 925 mb temperatures trending above
climatological normal, daytime temperatures will likely rise above
seasonal values, particularly across coastal and urban areas of
Puerto Rico and the U.S. Virgin Islands. This will result in a
gradual increase in heat risk by the end of the period, especially
in lower elevations.

In this pattern, periods of locally heavy rainfall and isolated
thunderstorms will be possible each afternoon, particularly where
sea breeze convergence and local effects combine. Residents and
visitors should anticipate warmer and humid conditions, increased
potential for ponding of water on roadways, and localized flooding
in flood-prone areas through the latter part of the forecast
period.

&&

.AVIATION...
(18Z TAFS)
Issued at 145 PM AST Mon Apr 20 2026

VFR conds across all TAF site thru the forecast period. Fm 20/18Z-21Z,
intermittent MVFR conds possible at TJBQ due to VCTS/-TSRA. E winds
at around 10 to 15 kts with gusts up to 20 to 25 kts and sea breeze
variations thru 20/22-23Z, becoming lighter overnight, then increasing
again by 21/13-14Z from the E-NE. VCSH across TIST/TISX/TJSJ during
the overnight period. Another round of -TSRA for TJPS fm 21/16-18Z.

&&

.MARINE...
Issued at 145 PM AST Mon Apr 20 2026

A high-pressure system over the north-central Atlantic will
promote gentle to moderate easterly winds, with seas in the 3 to 5
foot range tonight and Tuesday. Winds and seas will slightly
diminish Tuesday night. Then, due to a weak frontal boundary
positioned north of the region and a brief pulse of northerly
swell spreading across the Atlantic waters, winds will turn from
the northeast and seas will increase to 5 to 6 feet from Wednesday
night into Thursday. Small Craft will likely need to exercise
caution across the offshore Atlantic waters and local passages.
East to southeast winds will return by the end of the workweek.

&&

.BEACH FORECAST...
Issued at 145 PM AST Mon Apr 20 2026

There is a moderate risk of rip currents tonight along the north,
east, and southeast-facing beaches of Puerto Rico, Culebra, and
the U.S. Virgin Islands. By Tuesday, the moderate risk will prevail
along the northern coastline of Puerto Rico, Culebra, and St. Croix.
Beachgoers are encouraged to remain cautious, particularly in these
areas. As winds become lighter Tuesday evening into Wednesday, the
risk is expected to generally decrease. Late Wednesday night into
Thursday, a brief pulse of northerly swell is expected to spread
across the Atlantic waters, and the risk is anticipated to increase
to moderate or high along the northern coastline of Puerto Rico,
and to moderate along Culebra, St. Thomas, and St. John. Stay
tuned to the forecast for updates. For additional information and
location-specific rip current details, visit: weather.gov/beach/sju.

&&

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

$$

SHORT TERM...ERG
LONG TERM...CVB
AVIATION/MARINE/BEACH...YZR

NWS SJU Office Area Forecast Discussion