714
FXCA62 TJSJ 222027
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
427 PM AST Sat Feb 22 2025

.SYNOPSIS...

A northerly swell will produce life-threatening rip currents along
the north-facing beaches of Puerto Rico on Sunday and Monday.
Southeasterly winds return next week, promoting warmer than normal
temperatures across the lower elevations of the islands. Model
guidance suggests an increase in moisture by the end of next
week, with the proximity of a pre-frontal trough.


&&

.SHORT TERM...Tonight through Monday...

A weak surface trough and low level moisture are moving over the
region today. Showers over land were limited during the morning,
however, as most shower activity stayed over the waters. Light to
moderate showers moved over mainly northern and eastern sectors of
Puerto Rico during the early morning hours. By 10 AM to around noon,
a line of showers moved over the USVI, mainly affecting St. Thomas
and St. John. These showers then moved over Vieques and Culebra and
then reached eastern PR by around 2 PM AST. By this time, convective
showers already started to develop over western municipalities,
the Doppler radar estimated rainfall accumulations between
0.75-1.25 inches between Yauco and Mayaguez. These showers will
gradually tapper off this evening. Highs were in the mid to upper
80s across most lower elevation areas of the islands. Low
concentrations of Saharan dust were also present.

Satellite derived precipitable water (PWAT) values indicate a range
of 1.3 to 1.5 inches over most of the region (normal to high end
normal values), with another area of above 1.5 inches over the
Atlantic Waters. A patch of drier air, currently over the northern
Lesser Antilles, will move into the Anegada Passage late this
afternoon and over the islands tonight and into Sunday as the
surface trough moves westward, away from the region. Model guidance
suggests PWAT values decreasing to an inch or less, below normal
values, as this dry air moves in. The aforementioned patch of moist
air over the offshore Atlantic will remain tomorrow. This will limit
shower activity over windward sectors of the islands tonight into
Sunday. However, the sea breeze convergence, as well as diurnal
and local effects, will still promote limited afternoon convection
over western Puerto Rico.

By Monday, patches of more humid air embedded in the trade winds
will arrive, promoting low end normal to normal PWAT values. Morning
passing showers over windward sectors and afternoon convective
showers over W-NW PR are forecast as steering flow veers from
easterly to east-southeasterly. A surface high pressure moving into
the western Atlantic tomorrow will be in the central Atlantic to
start the workweek, tightening the pressure gradient and increasing
winds. 925 mb temperatures will be at to slightly above normal
values during the period.

.LONG TERM...Tuesday through Saturday...

A front stretching from the southwestern Atlantic into the north-
central Atlantic, and weakening of the surface high over the
central Atlantic will promote moderate (10-15 kt) southeasterly
winds through the long-term period. This will increase the likelihood
of warmer temperatures, particularly in the afternoons during
peak heating times. A mid-level ridge over the central Atlantic
extending into the northeastern Caribbean is expected to promote
drier air intrusion and overall stable conditions aloft. The best
moisture content will remain near the surface, with forecast
Precipitable water content values ranging from 1.25-1.50 inches
through most of the workweek. However, a weak surface trough on
Tuesday crossing the islands will lead to morning showers over the
USVI and east/southeast sections of PR, followed by stronger
afternoon showers along the interior and northern half of PR.

By the end of the week into the weekend, a wetter weather pattern
can unfold, as Puerto Rico and the US Virgin Islands will be in
the middle of an upper-level trough amplifying over the western
Caribbean and a ridge near the northeast Caribbean. Then, a
prefrontal trough associated with another frontal boundary moving
from the western Atlantic near the islands will pool better
moisture content over the area, with global models indicating
between 1.50-1.75 inches of Precipitable water content.


&&

.AVIATION...

(18z TAFs)

Mainly VFR conditions expected for the terminals. VCSH expected
during the evening, especially around TJPS and TJBQ due to SHRA over
interior to western PR. Winds decreasing after 22z, below 10 kts and
variable with land breezes, before increasing again from the E by
23/13-14Z to around 15 kts, with stronger gusts.


&&

.MARINE...

...Small craft advisories are in effect for the Atlantic waters
due to seas up 7 feet on Sunday...

Winds will continue to turn more east to northeast today as a
frontal boundary moves eastward across the western Atlantic. A
prefrontal trough will continue to increase the potential for showers
throughout the weekend. A surface high pressure building across
the central Atlantic will tighten the local pressure gradient,
promoting moderate to locally fresh winds early this upcoming
week. Increasing winds and a long period northerly swell will
deteriorate seas on Sunday.


&&

.BEACH FORECAST...

A 4 to 5 feet long period northerly swell will increase the risk
of rip currents on Sunday and Monday across the north-facing
beaches of the islands. A High Rip Current Risk is in effect for
the northern beaches of Puerto Rico, starting on Sunday morning.
Elsewhere, the risk will increase gradually as the swell spreads
further southward across the islands passages, and additional
coastal areas may be added to the High Rip Current Risk.


&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk from Sunday morning through Monday
     afternoon for PRZ001-002-005-008.

VI...None.
AM...Small Craft Advisory from 6 AM Sunday to 6 AM AST Monday for
     AMZ711.

     Small Craft Advisory from 6 PM Sunday to 6 AM AST Monday for
     AMZ712.

&&

$$

AVIATION/SHORT TERM...MRR
LONG TERM/MARINE/BEACH...DSR
PUBLIC...MNG