National Weather Service Today's Weather Impact Levels

978
FXCA62 TJSJ 201823
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
223 PM AST Sat Dec 20 2025

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

.KEY MESSAGES...
Issued at 200 PM AST Sat Dec 20 2025

* Frequent light to moderate showers will persist across the local
  islands for the rest of the day, with a limited flood threat
  across eastern and southwestern sections of Puerto Rico and
  some coastal areas of the U.S. Virgin Islands.

* A small craft advisory is in effect until 6 PM on Sunday, due to
  increasing winds and a northeasterly swell producing hazardous
  seas. Life-threatening rip currents are expected along the north
  and east facing beaches of the islands.

* For the Christmas week, a wet and unstable weather pattern is
  forecast with a high chance of widespread showers and
  thunderstorms. Residents and visitors are urged to stay tuned
  for further updates.

&&

.Short Term(This afternoon through Monday)...
Issued at 200 PM AST Sat Dec 20 2025

Sunny to partly cloudy skies prevailed across the islands today. A
band of showers moved over the islands early this morning,
crossing from east to west, leaving measurable rainfall amounts
across most areas. The Doppler radar estimated between 0.10-0.30
inches in general with this activity. By noon, this surge in
moisture combined with the sea breeze convergence to produce
heavier showers over the southwest quadrant of PR, and up to 1
inch was observed from Penuelas to Yauco. For the rest of this
afternoon, showers will continue to develop mainly over western
PR. In general, maximum temperatures were from the mid to upper
80s across the lower elevations of the islands. The wind was from
the northeast between 10 and 20 mph with higher gusts at times.

For the rest of the short-term period, patches of moisture
embedded in the trade winds will continue to bring passing showers
at times across the USVI and PR. A mid-to upper-level ridge
will continue to inhibit the vertical development of showers,
maintaining a low probability of thunderstorms. The overall drier
air layer aloft and warmer than normal 500mb temperatures, suggest
that fair weather conditions should prevail in general, with the
exception of the occasional trade wind shower moving over windward
areas. However, across western PR, and due to the enhancement of
the sea breeze convergence and daytime heating, heavier showers
are expected to develop each afternoon.

Minimum temperatures will range from the low 60s across the
higher elevations of PR, to the upper 60s and low 70s across the
lower elevations of the islands. Daytime highs will continue from
the mid to upper 80s across the southern and western lower
elevations of PR.

&&

.Long Term(Tuesday through next Saturday)...
Issued at 531 AM AST Sat Dec 20 2025

By the beginning of the long term, an upper-level trough tied to
the subtropical jet stream will bring cooler mid-level
temperatures as the mid-level ridge weakens and moves westward.
Patches of low level moisture will continue to move across the
area, resulting in isolated to scattered showers over windward
sections of Puerto Rico and the U.S. Virgin Islands, mainly during
the night and morning hours. By late morning into the afternoon,
a moderate chance of scattered showers, around 50 percent, is
expected across interior and western Puerto Rico with low chances
of flooding concerns.

For Wednesday and Thursday, Christmas Eve and Christmas Day,
atmospheric instability will increase somewhat as 500 mb
temperatures continue to cool further to below normal values
between -8 and -10 degrees Celsius. A polar trough will extend
southward into the Caribbean, while an additional upper-level
trough will interact with a surface frontal boundary north of the
region. The frontal boundary will move close to the area or cross
the region, allowing a slight increase in moisture, while enhanced
upper-level divergence. However, the global models have been
somewhat unstable from run to run, but the latest guidance is now
indicating less available moisture compared to yesterday.
Precipitable water (PWAT) values are trending closer to seasonal
levels, generally around 1.5 to 1.6 inches. Although some
uncertainty remains, the reduction in moisture has led to a slight
downward adjustment in rain chances. A moderate chance (around
50%) is expected for scattered showers with isolated thunderstorms.
Galvez-Davison Index values have also lowered, suggesting reduced
instability and supporting only a few isolated thunderstorms,
with convection remaining mostly shallow.

Friday and Saturday, models are suggesting drier-than-normal air,
leading to stable weather. Cooler temperatures are expected during
the holiday period, as indicated by a trend toward below normal
925 mb temperatures.

&&

.AVIATION...
(18Z TAFS)
Issued at 200 PM AST Sat Dec 20 2025

Mainly VFR conditions expected across all terminals during the
next 24 hours. However, quick passing -SHRA could move at times
across TJSJ/TJBQ and the USVI terminals. Tempo MVFR conds are
possible at TISX btw 21/04-10z. NE winds up to 19 kt blo FL100.

&&

.MARINE...
Issued at 200 PM AST Sat Dec 20 2025

No changes to previous forecasts.  Deteriorating marine conditions
are forecast from later today into the evening hours due to a north-
northeast swell filtering into the region. As a result, seas will
build up to 7-8 feet, especially across the offshore Atlantic waters
and local passages. As a result, there is a small craft advisory in
effect for the offshore Atlantic waters and the Anegada passage
until 6 AM AST on Sunday. For the rest of the local waters and seas,
waves will remain up to 5 feet. Improving marine conditions are
forecast for Tuesday into early Wednesday, when another northerly
swell moves into the area, deteriorating marine conditions again for
small craft operators.

&&

.BEACH FORECAST...
Issued at 200 PM AST Sat Dec 20 2025

For the rest of the day, a moderate risk of rip currents will
persist as coastal marine conditions deteriorate with the arrival of
the north-northeasterly swell. Therefore, from 6 PM AST onward,
there is a high risk of rip currents across all northern coastal
areas, including Culebra and St. Croix, until Monday evening.
Coastal conditions will improve by Tuesday; however, another
northerly swell will increase the risk up to high again by late
Wednesday into Thursday.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk from 6 PM AST this evening through late
     Sunday night for PRZ001-002-005-008-012.

VI...High Rip Current Risk from 6 PM AST this evening through late
     Sunday night for VIZ002.

AM...Small Craft Advisory until 6 PM AST Sunday for AMZ711.

     Small Craft Advisory from 6 PM this evening to 6 PM AST Sunday
     for AMZ723.

&&

$$

SHORT/AVIATION...DSR
LONG TERM...YZR
KEY/BEACH/MARINE...LIS

NWS SJU Office Area Forecast Discussion