008
FXCA62 TJSJ 031814
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
214 PM AST Mon Nov 3 2025

...New SHORT TERM, LONG TERM, AVIATION...

.KEY MESSAGES...
Issued at 207 PM AST Mon Nov 3 2025

* A trade wind perturbation will continue to produce shower
  activity with few isolated thunderstorms over portions of the
  interior, western and northern Puerto Rico.

* Patches of both, humid and drier air, will continue to move
  over the area during the week, before a tropical wave reaches
  the islands by next Sunday.

* Across the U.S. Virgin Islands, mainly fair weather conditions
  will prevail, with occasional passing showers.

* By the end of the workweek, a northerly swell is forecast to
  arrive, deteriorating marine and coastal conditions.

&&

.Short Term (This evening through Wednesday)...
Issued at 207 PM AST Mon Nov 3 2025

The trade wind perturbation resulted in periods of light to moderate
showers moving rapidly across the region during the early morning.
Most rainfall accumulations were under 0.5 inches, with a few
localized spots recording near 0.75 inches. Due to the quick
movement of the showers, no significant flooding occurred, only
minor ponding on roadways, reduced visibility, and slippery driving
conditions. Breezy conditions prevailed across coastal and exposed
areas, with wind gusts generally in the 20 to 25 mph range, and a
few stations reporting gusts over 30 mph.

Moisture associated with the departing perturbation will continue to
promote passing showers across eastern Puerto Rico and the U.S.
Virgin Islands through the afternoon. Daytime heating and local
effects will trigger additional convection across the interior and
western sections of Puerto Rico. Isolated thunderstorms are possible
but expected to be short-lived due to the stabilizing influence of a
mid-level ridge aloft. Model soundings indicate 500 mb temperatures
around -3 to -4C, warmer than normal, thus limiting vertical
instability and overall convective strength. Rainfall accumulations
should remain modest given the fast movement of showers and the lack
of strong upper-level support. Mostly ponding of water in roadways
and poor-drainage areas, although localized flooding cannot be ruled
out.

On Tuesday, the northern portion of a retrogressing TUTT will cross
the region, increasing favorable dynamics aloft. However, this will
coincide with a notable dry slot, with precipitable water values
dropping near 1.0 inch, below the 5th climatological percentile. As
a result, shower coverage will be minimal and mostly localized,
particularly across western Puerto Rico during the afternoon.

By Wednesday, interaction between the TUTT and its associated
surface-induced trough will coincide with a moisture surge, raising
precipitable water values to around 2.0 inches. This will lead to an
uptick in shower and thunderstorm activity, mainly across the
interior and western municipalities during the afternoon. Winds
shifting slightly to the east-southeast will bring somewhat warmer
temperatures, but an overall limited heat threat will prevail each
day, mainly across coastal and urban areas.

&&

.Long Term (Thursday through next Sunday)...
Issued at 532 AM AST Mon Nov 3 2025

High pressure systems over the central Atlantic will promote
generally easterly steering flow while a mid level ridge is expected
to persist north of the region, promoting stability and drier
conditions aloft. Patches of both moisture and drier air will
continue to filter in and out of the local area throughout the rest
of the week under this easterly steering flow, becoming more
southeasterly on Saturday as the surface high moves westward.
Precipitable water (PWAT) values are forecast to fluctuate between
below normal to normal values during the rest of the week. Leaving
passing showers over windward sectors of PR/USVI during the morning
and overnight hours with afternoon showers and t-storms possible
over mainly western Puerto Rico, as diurnal heating, sea breeze
convergence, and orographic effects promote this convection and a
limited flooding risk. An upper low will also be present to our SW
to start the period, gradually moving NE as the workweek continues.
This upper low will somewhat increase instability and could induce
weak surface troughs. Up to a limited heat risk is likely to persist
during the rest of the week. Available moisture will be confined to
the lower levels throughout the start of next week, when deeper
moisture arrives in the form of a tropical wave. By late Saturday
and Sunday, a tropical wave is forecast to move over the islands,
increasing PWAT values to above 2 inches (above normal values) as
well as promote up to breezy southeasterly steering flow over
windward sectors. Latest Galvez-Davidson Index (GDI) values are up
to around +40 on Sunday, suggesting a potential for scattered t-
storms, heavy rain and an increased flooding risk. Lingering
moisture will persist on Monday under southeasterly steering flow.

&&

.AVIATION...
(18Z TAFS)
Issued at 207 PM AST Mon Nov 3 2025

Mainly VFR conditions will prevail across all TAF sites through the
period. However, brief SHRA and isolated TSRA are expected to
develop over interior and western PR thru 23z, potentially affecting
the VCTY of TJBQ/TJPS. VCSH will persist across eastern PR terminals
and the USVI through the evening hours, with activity diminishing
after sunset. Brief MVFR conds possible at all TAF sites. E to ESE
winds at 10 to 20 kt with gusts up to 25 kt will continue through
22Z, becoming lighter and variable overnight.

&&

.MARINE...
Issued at 207 PM AST Mon Nov 3 2025

A surface high pressure over the central Atlantic will promote
moderate to locally fresh easterly trade winds until mainly this
evening as well as wind-driven, choppy seas. Small Craft should
Exercise Caution over the Atlantic waters, the Mona & Anegada
Passages and the Offshore Caribbean Waters today. Decreasing winds
and subsiding seas are forecast by later tonight and until at
least Thursday. By Thursday and Friday a northerly swell will
deteriorate marine conditions, Small Craft Should Exercise Caution
during these days over exposed Atlantic waters.

&&

.BEACH FORECAST...
Issued at 207 PM AST Mon Nov 3 2025

There is a moderate risk of rip currents today for the northern,
eastern, southeastern, and some southern beaches of Puerto Rico. A
moderate risk of rip currents will also persist today for St.
Thomas, St. John, St. Croix, Culebra and Vieques.

Coverage of this moderate risk of rip currents will decrease
tonight and throughout mid-week, but will persist mainly over
northern exposed beaches of Puerto Rico and Culebra. St. Croix`s
moderate risk of rip currents will continue until late tonight.

A northerly swell will is expected to arrive by the end of the
workweek, deteriorating coastal conditions, once again increasing
the coverage of the moderate risk of rip currents to most of the
above mentioned areas with some northern exposed beaches possibly
reaching a high risk of rip currents on Friday. For additional
updates, visit weather.gov/beach.

&&

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

$$

MORNING SHIFT...CVB/GRS
EVENING SHIFT...DSR/MNG