National Weather Service Today's Weather Impact Levels

148
FXCA62 TJSJ 032013
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
413 PM AST Thu Apr 3 2025

.SYNOPSIS...

The main hazard will be the windy conditions, with sustained
winds of 20 to 30 mph and gusts potentially exceeding 40 mph,
possibly reaching up to 50 mph in localized areas through at least
late Friday. These will promote hazardous marine and coastal
conditions.

&&

.SHORT TERM...Tonight through Friday...

The local meteorological network detected windy easterlies in Puerto
Rico and the U.S. Virgin Islands. Winds fluctuated between 20 and 30
mph with gusts between 35 and 45 mph, but locally higher in other
places cannot be ruled out. The Doppler Radar detected frequent
showers moving across the local waters, and some of them moved
inland, mainly across eastern half of Puerto Rico, Vieques,
Culebra, and the U.S. Virgin Islands. Maximum values reached the
low 90s, mainly across the southwest coastal locations of PR.

The surface high pressure across the Central Atlantic, tightening
the local pressure gradient, will promote a breezy to windy trade
winds pattern over the weekend. Winds will slowly diminish from
Friday evening onward. Thus, a Wind Advisory is in effect until
Friday night due to sustained winds of 20 to 25 mph, with frequent
gusts ranging from 35 to 45 mph and possibly reaching up to 50 mph.
Additionally, the easterly winds will carry patches of moisture,
leading to rain showers each day. As a result, we cannot rule out
the possibility of moderate to locally heavy rain at times.

Instability will increase due to an amplifying mid- to upper-level
trough, which could promote the formation of better convection,
giving place to thunderstorms, especially on Saturday afternoon over
western PR. However, the limiting factor is a dry air mass at mid-
levels, which could promote subsidence aloft and less potential for
widespread activity.

Life-threatening rip currents are expected to form daily at local
beaches. Residents and visitors are strongly urged to follow the
guidance of lifeguards and beach patrols. As a result, a high rip
current risk is in effect for the east and north-facing beaches of
Puerto Rico and the U.S. Virgin Islands, with occasional rip
currents also possible along the south and west coasts.

.LONG TERM...Sunday through Thursday...
//from previous discusion//

Starting the long-term period, winds will continue to subside,
allowing hazardous marine and coastal conditions to improve, at
least through next Monday. Latest model guidance continues to
suggest that a surface high-pressure over the western Atlantic
will move eastward into the Central Atlantic from Sunday into
early next week, promoting east to northeast winds to become more
easterly from Monday onward. An upper-level trough will persist
over the region through the forecast period, promoting ventilation
and cooler temperatures aloft, with 500 mb temperatures remaining
between -8C and -10C. These conditions will support favorable
conditions for deep convection and increase the chances of
thunderstorm development. However, moisture content will be
limited across different levels of the atmosphere, which could
inhibit significant rainfall and afternoon thunderstorms. Models
suggest that precipitable water values will oscillate between
below 1.0 and 1.5 inches through Tuesday, which is considered
below normal to near average. As a result, activity will likely
depend on the arrival of patches of moisture, leading to periods
of sunshine and passing showers each day. Local effects and
favorable conditions aloft will likely produce isolated to
scattered convection, with a thunderstorm or two, during the
afternoon hours across the western portions of Puerto Rico each
day. However, at the moment, significant accumulations are not
expected. By Wednesday, the arrival of a band of moisture will
produce better rain chances. From Thursday afternoon/night onward,
it seems that we will transition into a wetter pattern due to the
combination of an approaching surface frontal boundary, a pre-
frontal trough, and the arrival of abundant tropical moisture
under southeasterly wind flow across the islands. This will likely
increase the frequency and chance of showers by the end of next
week.

&&

.AVIATION...
(18Z TAFs)

VFR conditions will be prevalent. Occasional -SHRA/SHRA/+SHRA may
impact local terminals, potentially causing brief MVFR or IFR conds,
particularly in windward areas. Winds will primarily be from the E
to ENE at 20-25 knots, with gusts ranging from 35 to 45 kt and
possibly even higher. After 03/23z, winds are expected to decrease
to around 15 knots but with higher gusts. Similar conditions are
anticipated to return after 04/13z. Additionally, a Wind Advisory is
in effect for the islands.

&&

.MARINE...

A broad surface high pressure over the western Atlantic will continue
to promote fresh to locally strong east to east-northeast winds
through at least late Friday night, then conditions will gradually
improve Saturday into Sunday. Today, seas will continue to build
between 6 to 10 feet, and occasionally higher, across most waters
resulting in hazardous seas over the next few days.

&&

.BEACH FORECAST...

A broad surface high pressure over the western Atlantic is producing
strong winds across our area, especially in coastal areas through
late Friday. This will maintain coastal conditions deteriorated
through at least Saturday. For that reason, a High Rip Current
Risk remains in effect through Saturday afternoon for the north-
facing beaches of Puerto Rico, from Aguadilla to Fajardo, Culebra
and the U.S. Virgin Islands. Also, from tonight through at least
Friday evening there will be a High Rip Current Risk for the
beaches of southeastern Puerto Rico, from Salinas to Yabucoa, and
Vieques. A Moderate Risk is in place elsewhere.

Swimmers are urged to exercise caution by staying near lifeguards
or even better to stay out of the water. Rip Currents can sweep
even the best swimmers away from shore into deeper water, where it
becomes difficult to return to safety. Heed the advice of lifeguards,
beach patrol flags and signs.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Wind Advisory until 8 PM AST Friday for PRZ001>013.

     High Rip Current Risk through Saturday afternoon for PRZ001-002-
     005-008-012.

     High Rip Current Risk through Friday evening for PRZ003-013.

VI...Wind Advisory until 8 PM AST Friday for VIZ001-002.

     High Rip Current Risk through Saturday afternoon for VIZ001-002.

AM...Small Craft Advisory until noon AST Saturday for AMZ711-712-716-
     723-726-733-741.

     Small Craft Advisory until 6 AM AST Friday for AMZ735-742-745.

&&

$$

SHORT TERM...CAM/MMC/ICP
LONG TERM...YZR
AVIATION...CAM/ICP
MARINE/BEACH FORECAST...MMC

NWS SJU Office Area Forecast Discussion