National Weather Service Today's Weather Impact Levels

774
FXCA62 TJSJ 171841
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
241 PM AST Tue Mar 17 2026

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

.KEY MESSAGES...
Issued at 240 PM AST Tue Mar 17 2026

* Hazardous marine and coastal conditions will persist through
  much of the week. Small Craft Advisories remain in effect for
  several local waters, and a high risk of rip currents is
  expected for many beaches of Puerto Rico and the U.S. Virgin
  Islands.

* Breezy to windy easterlies will continue through at least
  Wednesday night.

* Passing showers will increase across the U.S. Virgin Islands
  and eastern PR late this afternoon into the evening.

* A frontal boundary and associated trough will increase shower
  activity from late this week into the weekend, bringing periods
  of unsettled weather across Puerto Rico and the U.S. Virgin
  Islands.

&&

.Short Term(This evening through Thursday)...
Issued at 240 PM AST Tue Mar 17 2026

Once again, this morning, we had variable conditions from mostly
sunny skies across the PR`s western half and St Croix to partly
sunny and partly cloudy skies across portions of the eastern half
of PR, and the US Virgin Islands. A strong surface high-pressure
system promoted windy conditions across the islands, with weather
stations reporting sustained winds of 15 to 25 mph, gusting to 25
to 35 mph or higher. Maximum temperatures ranged from the mid- to
upper 80s along the coast to the lower 80s across the mountains.

This afternoon, breezy to windy conditions will continue, with
gusts reaching up to 35 mph. Under this wind pattern, brief
periods of moderate to heavy rain will primarily affect the U.S.
Virgin Islands and the windward areas of Puerto Rico, leading to
occasional periods of moderate to locally heavy rain. However,
expect periods of sunshine and mostly clear skies overnight.
Limited showers may reach western Puerto Rico, but most rainfall
is anticipated in the windward areas. By this evening, moisture
levels will increase again with the arrival of a weak
perturbation, bringing showery weather to some windward areas.
Additionally, winds will gradually ease late tonight through early
Wednesday morning, decreasing to around 15 to 20 knots as the
local pressure gradient relaxes.

By Thursday, the pattern will begin to shift toward a more
unstable, wetter pattern, with moisture rising into the mid levels
of the atmosphere over the islands. Meanwhile, trade winds will
continue to weaken, with 925 mb winds decreasing to around 1017
knots. The combination of lighter steering flow and increasing
moisture should support a more typical shower pattern across the
region and stronger afternoon convection.

&&

.LONG TERM...
Issued at 258 AM AST Tue Mar 17 2026

Variable conditions are expected in the long-term forecast. A broad
surface high pressure over the Central Atlantic will promote winds
with a southerly component, with patches of moisture across the CWA
on Friday. This will bring passing showers over windward sections in
the morning, with afternoon showers over north/northwestern Puerto
Rico. Rainfall accumulations should remain limited, leading to
ponding of water over roadways and poorly drained areas.

Weather conditions will likely become wetter and more unstable in
the upcoming weekend, as a deep-layered trough with an associated
frontal boundary will likely approach the region by Saturday,
inducing a pre-frontal trough that will likely increase shower and
thunderstorm activity. Additionally, a col region will move
across the region by Saturday, with 925 mb winds plummeting to
well below normal (mostly variable and calm winds). According to
the latest model guidance, Precipitable Water values are expected
to range between 1.5 and 1.75 inches, which is above the
climatological normal, with the best moisture content in the low
and mid levels (above 70%), increasing chances of scattered to
numerous showers. Additionally, weakening winds will result in
stationary showers and thunderstorms, with the highest potential
of flooding on Saturday and Sunday.

Due to the approach of the trough, the mid-level temperatures
should slightly cool (around -8 degrees Celsius), with a jet
streak positioning over the region, allowing ventilation aloft
(between 70 and 90 kt). Although the best of convection should
remain north of the CWA, conditions will likely be favorable for
deeper convection and increasing lightning potential. Therefore,
the most likely scenario is an advective pattern on both Saturday
and Sunday, with afternoon convection over the mountain ranges of
Puerto Rico. Rainfall accumulations will likely result in urban
and small streams flooding, with a low chance of flash flooding,
over the aforementioned areas.

By Monday, another surface high pressure exiting eastern CONUS
will increase pressure gradient, promoting E- ENE winds. Weather
conditions should gradually improve; however, remaining moisture
content should be enough for the development of showers across the
regional waters into windward sections throughout the day, along
with afternoon convection. Residents and visitors are encouraged
to continue to monitor the weather forecast due to discrepancies
between global solutions.

Although Friday will likely be the warmest day of the long-term,
maximum temperatures should remain in the mid to high 80s, with
localized low 90s, across low elevation areas of the islands, with
no heat threat expected.

&&

.AVIATION...
(18Z TAFS)
Issued at 240 PM AST Tue Mar 17 2026

Mainly VFR conditions will prevail under E to ESE flow at 15 to 25
kts with higher gusts at 27 to around 30 kts. By 17/20Z -SHRA/VCSH
will be steered towards the USVI terminals, and shortly after the
eastern PR terminals. This can lead to brief MVFR cigs and mostly
VCSH/-RA periods. Winds decreasing somewhat after 17/23Z, especially
for PR terminals, increasing again after 18/13Z.

&&

.MARINE...
Issued at 240 PM AST Tue Mar 17 2026

Strong high pressure over the central Atlantic will maintain fresh
to strong easterly winds and choppy to rough seas across the
northeastern Caribbean waters. A weak easterly perturbation will
increase passing showers tonight. By late week, a frontal boundary
moving eastward across the western Atlantic will weaken the local
pressure gradient, allowing winds to gradually diminish while a
pre-frontal trough near Hispaniola increases moisture and promotes
more unsettled conditions from late Thursday into the weekend.

&&

.BEACH FORECAST...
Issued at 240 PM AST Tue Mar 17 2026

Beach conditions will remain hazardous for inexperienced swimmers
across much of the local islands. Breezy to windy easterly winds
will continue to generate choppy to rough seas across the regional
waters, increasing wave action along exposed beaches. As a
result, a high risk of rip currents will persist along many
exposed beaches in PR and the USVI through much of the week.

Beachgoers should exercise caution, remain aware of changing
coastal conditions, and monitor the latest forecasts and
statements. For additional information, visit:
weather.gov/beach/sju

&&

.FIRE WEATHER...
Issued at 240 PM AST Tue Mar 17 2026

A Fire Danger Statement (RFDSJU) remains in effect for the
coastal plains of southern Puerto Rico. The KeetchByram Drought
Index (KBDI) remains elevated, with values around 687 in Cabo Rojo
and 552 in Gunica, indicating increasingly dry fuels.

East to east-southeast winds of 15 to 22 mph, with gusts up to 30
mph, will continue the rest of the day. Although a few showers
cannot be ruled out, RH values will continue around 4555 percent
across the southern coastal plains.

The aforementioned dry fuels, gusty winds, and lower relative
humidity are supporting elevated fire weather conditions across
southern Puerto Rico today.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through Wednesday afternoon for PRZ001>003-
     005-007-008-011>013.

VI...High Rip Current Risk through Wednesday afternoon for VIZ001-002.

AM...Small Craft Advisory until 6 PM AST Wednesday for AMZ711-712-716-
     723-726-733-735-741.

&&

$$

KEY MESSAGES/SHORT TERM/MARINE/BEACH FORECAST/FIRE WEATHER...CAM
LONG TERM....MNG
AVIATION...MRR

NWS SJU Office Area Forecast Discussion