Your Number One Source for Real-Time Puerto Rico Weather & Hurricane Tracking Updates

709
FXCA62 TJSJ 210709
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
309 AM AST Sat Mar 21 2026

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

.KEY MESSAGES...
Issued at 304 AM AST Sat Mar 21 2026

 *  Today, southerly winds will contribute to above-normal
    daytime temperatures and limited shower activity, with
    cloudiness increasing through the afternoon hours.

 *  A more unsettled weather pattern is forecast from late tonight
    into Sunday, as shower and thunderstorm activity associated
    with an approaching frontal boundary and its induced surface
    trough moves into the CWA. These conditions may lead to
    localized flooding & lightning hazard.

 *  Northerly winds are expected to develop Monday into early
    Tuesday following frontal passage.

  * A low to moderate risk of rip currents exists across the
    coastal waters of Puerto Rico and the U.S. Virgin Islands.


&&

.Short Term(Today through Monday)...
Issued at 304 AM AST Sat Mar 21 2026

A quite warm and stable night was observed across the islands. A
light southerly wind flow persisted during the night and early
morning hours. Some clouds with showers were observed by Doppler
radar and satellite imagery over the Caribbean coastal waters. As
of 2 AM AST, the Doppler Radar showed light to moderate showers
affecting the municipalities of Ponce and vicinity, leaving
minimal rainfall accumulations. In terms of temperatures, the
values remained just slightly above the climatological normals,
with minimum temperatures in the upper 70s along the coast and in
the upper 60s across the mountains, according to unofficial
stations.

For the rest of the day, variable weather conditions will prevail
across the region under a southerly wind flow ahead of an
approaching surface frontal boundary and its associated pre-
frontal trough. In response to this evolving pattern, warmer-than-
normal conditions are expected, with daytime temperatures rising
approximately 2 to 3 degrees above climatological averages.
Initially, relatively stable conditions will dominate during the
morning hours; however, cloud cover will gradually increase as the
frontal boundary continues to sink southward toward the islands.
At the same time, moisture levels will rise, with precipitable
water values increasing to around 1.3 to 1.5 inches by late
morning and persisting through the remainder of the day. In
combination with the pre-frontal trough and cooler temperatures
aloft at 500 mb near -7C, development of showers its forecast
across the southeastern quadrant of Puerto Rico, as indicated by
high-resolution model guidance.

Looking ahead, a wetter pattern is expected to become established
by early Sunday as deeper moisture associated with the frontal
boundary spreads across the forecast area from west to east, with
showers and isolated thunderstorms reaching western Puerto Rico
around 2 AM before gradually expanding across the remainder of the
islands throughout the day. Consequently, mostly cloudy skies
with periods of light to moderate rainfall are anticipated.
Furthermore, the presence of the induced surface trough will
weaken the pressure gradient, resulting in winds shifting to a
west-southwesterly direction and decreasing in speed, which will
favor slower-moving shower activity and increase the potential for
higher rainfall accumulations. As a result, there is a moderate
risk of urban flooding and rapid rises in small streams across the
islands. By Monday, following the passage of the frontal
boundary, winds are expected to veer to the north-northeast,
promoting the advection of drier air and a more stable atmospheric
profile, which will gradually reduce moisture levels and limit
rainfall activity; although isolated showers may still develop
over local waters and occasionally affect the northeastern coast,
no significant flooding concerns are anticipated across the
islands.

For the U.S. Virgin Islands, Saturday will bring partly cloudy
skies with only a few isolated showers. By Sunday, mostly cloudy
conditions will prevail with more frequent passing showers as the
frontal boundary settles over the region. The wet pattern will
intensify into Monday, with shower activity becoming more
persistent and organized as disturbances move in and out of the
area.

&&

.Long Term(Tuesday through Saturday)...
Issued at 304 AM AST Sat Mar 21 2026

A broad mid- to upper-level trough will persist across the western
Atlantic and northeastern Caribbean through the period, maintaining
unsettled conditions across Puerto Rico and the U.S. Virgin Islands.
Moisture will remain near to above normal throughout the period.

On Wednesday, lighter steering flow and sufficient moisture will
favor slow-moving showers, particularly across windward areas during
the morning and over the interior and western portions of Puerto
Rico during the afternoon. Thunderstorms are possible, with locally
heavy rainfall that may lead to urban and small stream flooding as
well as frequent lightning.

From Thursday onward, moisture will deepen across the region while
500 mb temperatures remain below -8 degrees Celsius, resulting in a
more unstable atmosphere. This combination of cold air aloft and
abundant moisture through a deep layer will promote more efficient
rainfall processes and an increased coverage of showers and
thunderstorms each day. Periods of heavy rain will maintain an
elevated risk of flooding, especially in areas that receive repeated
rounds of precipitation. Gusty winds will be possible in and near
heavier showers, while saturated soils will increase the likelihood
of flooding, ponding of water on roadways, and minor landslides in
steep terrain.

Overall, an extended period of unsettled weather is expected from
midweek through Saturday, driven by persistent troughing aloft, cold
mid-level temperatures, abundant moisture at all levels, and
periodic disturbances moving through the region.

&&

.AVIATION...
(06Z TAFS)
Issued at 304 AM AST Sat Mar 21 2026

VFR conditions will persist, with brief MVFR conditions. Winds
will remain VRB at 5 kts, gradually increasing to 8 to 10 kts from
the S by 21/14Z. An approaching surface frontal boundary will
result in lowering CIGS from 21/18Z onward as it sinks S into the
CWA. Scattered -RA and SHRA, with possible VCTS, are expected to
reduce VIS at TJPS between 21/19Z and 21/21Z. By 22/03Z, SHRA and
VCTS with lower ceilings and reduced visibility are anticipated at
TJBQ, with conditions potentially deteriorating to IFR.

 &&

.MARINE...
Issued at 304 AM AST Sat Mar 21 2026

Light to moderate southeast winds will continue across the regional
waters through at least today, maintaining light to moderate chop
seas. A pre-frontal trough and associated boundary approaching from
the northwest will weaken the pressure gradient, allowing winds to
diminish and shift through the rest of the weekend. Periods of
unsettled weather will also increase shower activity and the
potential for thunderstorm development across the local waters,
especially from this afternoon into the overnight hours. By early
next week, high pressure building over the western Atlantic will
promote a return to northeasterly winds and increasing seas, leading
to deteriorating marine conditions.

&&

.BEACH FORECAST...
Issued at 304 AM AST Sat Mar 21 2026


Beach conditions have gradually improved as winds and seas have
diminished across the coastal waters. However, a MODERATE risk of
rip currents will persist through the weekend and much of the
forecast period, mainly affecting the northern and eastern beaches
of Puerto Rico, including Culebra, as well as the U.S. Virgin
Islands. A moderate risk means that life-threatening rip currents
remain possible, particularly for inexperienced swimmers. Beachgoers
should remain cautious, stay near lifeguards, and avoid entering the
water if unsure of conditions. A high risk of rip currents may be
observed across northwest PR on Sunday.

Lower risk conditions are expected along the more protected southern
beaches, though caution is still advised.

In addition, increasing moisture and instability associated with an
approaching frontal boundary will promote periods of showers, and
isolated thunderstorms cannot be ruled out, mainly from this
afternoon into Sunday. Localized impacts, such as reduced visibility
and brief gusty winds, may occur near showers, creating sudden
hazardous conditions for beachgoers. There is a limited
thunderstorm risk, but any storms that develop could produce
lightning, posing a danger to those in or near the water. If
thunderstorms approach, seek shelter immediately. For additional
information and location-specific rip current details, please
visit: weather.gov/beach/sju

&&

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

$$

SHORT TERM & AVIATION...LIS
LONG TERM....MMC
MARINE & BEACH FORECAST...CAM

NWS SJU Office Area Forecast Discussion