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393
FXCA62 TJSJ 181832
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
232 PM AST Tue Nov 18 2025

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

.KEY MESSAGES...
Issued at 220 PM AST Tue Nov 18 2025

* Life-threatening rip currents are expected along the north-
  facing beaches in Puerto Rico, Culebra, and the eastern half of
  St. Croix through Wednesday afternoon.

* Showers and isolated thunderstorms this afternoon due to a
  surface trough, then a showery pattern will stretch into
  Wednesday morning across windward areas.

* Passing showers will bring periods of moderate to locally heavy
  rain across the US Virgin Islands during the overnight period.

* Drier air and cooler temperatures are anticipated by Thursday
  into the weekend.

&&

.Short Term(This evening through Thursday)...
Issued at 220 PM AST Tue Nov 18 2025

The most recent satellite imagery shows an area of enhanced
moisture, associated with a surface trough, reaching the Virgin
Islands and eastern Puerto Rico. The high resolution and global
models, as well as current observations, suggest that shower
activity will keep streaming across the Virgin Islands, and
eastern Puerto Rico this afternoon, with a low chance of
experiencing urban flooding and lightning strikes. Across the
interior and western Puerto Rico, while convection is expected to
be heavy at times, showers will taper off by sunset, giving way to
mostly clear to partly cloudy skies in the night hours.

The surface trough will depart the northeastern Caribbean islands by
early tomorrow, so the showery pattern will stretch into Wednesday
morning. Then, as a high pressure build at the mid levels over the
western Caribbean, a much drier and cooler air mass will filter in.
However, there should be enough energy to generate locally strong
convection along western Puerto Rico on Wednesday afternoon, but
conditions will gradually improve afterward. At the surface, the
trade winds will stay from the northeast while weakening. Under this
pattern, it is usual that showers pop up over the Atlantic waters in
the late night and early morning hours. These showers will then
reach the northeast coast of Puerto Rico and the Virgin Islands at
times, but without posing a flooding risk.

&&

.Long Term(Friday through Tuesday)...
Issued at 348 AM AST Tue Nov 18 2025

The long-term forecast remains on track, with mostly fair conditions
for the upcoming weekend, becoming variable early next week. A
surface high pressure is still expected to build over the Western
Atlantic by Friday, promoting northeasterly winds through most of
the period. As a drier air mass should filter into the region, the
latest deterministic guidance from the GFS and ECMWF continues to
suggest PWAT values mostly below climatological normal (1.2 - 1.4
inches), with a few members opting for more seasonal values (1.4 -
1.6 inches). A mid-level ridge should also establish, warming 500 mb
temperatures (around -5.5 degrees Celsius), and promoting stability
aloft and limiting deep convection activity. Additionally, the
Galvez-Davison Index (GDI) suggests a low potential of thunderstorm
development across the CWA. As mentioned in the previous discussion,
the most likely scenario would be passing showers over windward
sections in the late night and morning, with limited afternoon
convection over the mountain ranges and southwestern portions of
Puerto Rico. Although rainfall accumulations should not present a
flooding threat, expect ponding of water over roadways, urban, and
poorly drained areas. On Monday and Tuesday, PWAT values are
expected to increase to more seasonal levels due to patches of
moisture moving across the CWA, resulting in an increased frequency
of showers. Nevertheless, no significant flooding or lightning risk
is expected across the region.

Once again, cooler temperatures are likely across the CWA during the
forecast period, as the latest guidance keeps suggesting a fall in
925 mb temperatures, well below normal. Under a northeast wind flow,
the heat threat will remain low throughout the long-term period.

&&

.AVIATION...
(18Z TAFS)
Issued at 220 PM AST Tue Nov 18 2025

VFR with intermittent MVFR conds possible over the next hours.
VCTS or TSRA will result in reduced vis and lower cigs, then will
decrease aft 18/22-23Z but may linger near TJSJ and USVI
terminals overnight. Winds will remain from the E with gusts at
around 18 to 21 kts. Typical sea breeze variations and locally
gusty winds near t-storms. Lighter winds overnight, increasing
near 10 kts aft 19/13-14Z.

&&

.MARINE...
Issued at 220 PM AST Tue Nov 18 2025

A surface trough will continue to bring showers and isolated
thunderstorms across the local waters and passages tonight into
Wednesday morning, likely generating localized hazardous conditions
for small craft. Moderate easterly winds will persist through
Wednesday night before shifting to the northeast as a surface
trough moves east of the Leeward Islands. Pulses of a north-
northeasterly swell will continue to spread across the Atlantic
waters and local passages through Wednesday.

&&

.BEACH FORECAST...
Issued at 220 PM AST Tue Nov 18 2025

Pulses of north-northeasterly swells continue to spread across the
local Atlantic waters. Current observations from the San Juan buoy
are variable, with wave heights around 3 feet at periods pulsing
up to 10 to 14 seconds. Based on calculations, this is producing
breaking waves of around 6 feet, maintaining a high risk of rip
currents along the northern and eastern beaches of Puerto Rico, as
well as Culebra and St. Croix, through this evening and potentially
through at least Wednesday afternoon. For location- specific
information, visit weather.gov/beach/sju.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through Wednesday afternoon for PRZ001-002-
     005-008-012.

VI...High Rip Current Risk through Wednesday afternoon for VIZ002.

AM...None.
&&

$$

SHORT TERM...ERG
LONG TERM...MNG
AVIATION...YZR

NWS SJU Office Area Forecast Discussion