874
FXCA62 TJSJ 280848
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
448 AM AST Fri Feb 28 2025

.SYNOPSIS...

Shower activity will continue to reach windward sectors this
morning as patches of moisture filter in and a trough is near the
region. During the afternoon, stronger shower activity is
forecast for mainly northwestern Puerto Rico. Saturday looks like
a transition day as a wide area of drier air approaches from the
Lesser Antilles. As the environment dries out, minor
concentrations of Saharan dust will filter in, creating hazy
skies. East- southeast winds will increase during the weekend. A
mid to upper- level trough will approach the northeast Caribbean
during the early to mid part of the next workweek, followed by a
surface frontal boundary by the end of the next workweek.

&&

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

A small area of moisture approached St. Croix around midnight, and
eastern Puerto Rico early in the morning hours. These showers were
not strong, only leading to wet roads and ponding of water in low-
lying areas. Temperatures cooled down to the low and mid-70s in
coastal areas, and into the low 60s (cooler in isolated spots) in
the mountain. Right now, the axis of the surface trough is centered
just to the south of Puerto Rico, hence winds have shifted from the
southeast. This feature will move additional showers into the Virgin
Islands and eastern Puerto Rico this morning.

At the low and mid levels, high pressure centered over the eastern
Atlantic will keep these winds coming from the southeast through the
forecast period. Today, near normal moisture will combine with
diurnal heating, creating streams of showers that will reach the
Virgin Islands, and the east and northwest of Puerto Rico, as well
as the San Juan metropolitan area. The heaviest activity is
anticipated for the northwest, where minor urban and small stream
flooding could develop. Saturday looks like a transition day between
the moisture brought by the surface troughs and a wide area of drier
air approaching from the Lesser Antilles. It is likely that showers
will also develop Saturday afternoon, but more confined to the
northwestern quadrant of Puerto Rico. As the environment dries
out, minor concentrations of Saharan dust will filter in, creating
hazy skies. These conditions will continue into Sunday, with some
brief shower interruptions, particularly for the easternmost
sections of Puerto Rico, as well as the Virgin Islands.

It will be warmer than normal too, especially during the afternoon
hours. The 925-mb temperature values are about one standard
deviation above the climatological mean. Even with cooling still
happening in the overnight hours, the highs will climb to the low
and mid 80s in low-elevated areas, and into the upper 70s and low
80s in the highest mountains.

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

Both pockets of more humid and pockets of drier air will reach
the region Monday and early Tuesday. Low saharan dust
concentrations will also move into the region on Monday,
resulting in hazy skies, and linger through at least Tuesday. In
the mid to upper levels, a high pressure will be present
throughout early Tuesday, before an trough moves in Tuesday and
into late Wednesday, increasing instability. Current model
guidance suggests that the trough will be well east by Thursday
and Friday. A series of surface highs and frontal lows will move
into the western to central Atlantic during the period, resulting
in east to east- southeast flow over the islands. This windflow
will steer more frequent patches of moisture into our area by
Tuesday onwards. Precipitable water (PWAT) values will be above
1.5 inches (above normal) with these moist patches. Moisture from
a frontal boundary north of the area could also reach us by
Friday. Most available moisture should by below 700 mb, during the
period. A variable weather pattern will include overnight and
early morning showers steered towards along eastern and southern
coastal sections of the islands with afternoon convection forecast
to focus across the central interior and north/northwest sectors
of Puerto Rico. With the approach of an upper-trough and
increasing moisture, and boost in this pattern is forecast by
midweek. 925 mb temperatures will be up to above normal values
during the period.

&&

.AVIATION...

(06z TAFS)

SHRA will move across the Caribbean waters, occasionally
reaching the USVI and TJSJ terminals. After 17Z, showers will also
develop across TJBQ. These showers could lead to brief periods of
reduced VIS and low ceilings, especially for TJBQ. Mountain
obscuration across the Cordillera Central is also expected from 17-
22Z. Winds will be from the ESE at 11-17 kts, with stronger gusts.

&&

.MARINE...

A surface trough with an axis centered just south of the region and
a broad surface high pressure over the eastern Atlantic will promote
up to moderate east-southeast winds. As the surface high pressure
builds over the Atlantic the local pressure gradient will tighten,
promoting a moderate to locally fresh east-southeast wind flow late
tonight and throughout the weekend. This could promote Small Craft
Should Exercise Caution criteria over some areas.

&&

.BEACH FORECAST...

A moderate risk of rip currents is forecast for today and tonight
for the north oriented beaches of Puerto Rico, from Aguadilla to
Rincon, northern Culebra and easternmost St. Croix. The risk for rip
currents is low elsewhere, however, life-threatening rip currents
often occur in the vicinity of groins, jetties, reefs, and piers.
The increasing winds expected for the weekend, will maintain up to a
moderate risk of rip currents for the islands.

&&

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

$$

SHORT TERM...ERG
LONG TERM....MRR