701
FXCA62 TJSJ 031726
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
126 PM AST Wed Dec 3 2025

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

.KEY MESSAGES...
Issued at 120 PM AST Wed Dec 3 2025

* A surface trough over the eastern Caribbean will move across the
  local area through Thursday, this will increase showers and the
  potential for flooding across Puerto Rico.

* Across the U.S. Virgin Islands, shower activity will increase
  from tonight through Thursday morning due to the trough
  passage. Periods of locally moderate to heavy rain could lead to
  ponding of water in roads and minor flooding.

* A moderate risk of life-threatening rip currents is expected
  through the weekend under the influence of an easterly swell and
  increasing winds. Especially across the east and north facing
  beaches of the islands.

* Fair weather conditions are expected to return on Friday into
  early in the weekend.


&&

.Short Term(This afternoon through Friday)...
Issued at 120 PM AST Wed Dec 3 2025

Mostly sunny to partly cloudy skies prevailed across Puerto Rico
and the U.S. Virgin Islands today. Showers were developing around
noon over portions of the Cordillera and eastern PR. Streamers
developed off the USVI, leaving minor rainfall accumulations over
land areas. As of 1 PM, maximum temperatures were from the mid
and upper 80s across the lower elevations of the islands, and from
the upper 70s to mid 80s across the higher mountains of Puerto
Rico. The wind was from the east to southeast between 10 and 15
mph with sea breeze variations and higher gusts across coastal
areas.

For the rest of the afternoon hours, locally induced showers and
isolated thunderstorms are expected to develop along the interior
and western PR. This activity can lead to ponding of water on
roads and minor flooding. Meanwhile, a broad surface trough over
the eastern Caribbean will continue to move westward through
Thursday, increasing moisture content and the potential for
locally heavy rainfall over the islands, particularly from tonight
across the USVI, and through Thursday over PR. The main weather
hazards will be flooding and possible strong gusty winds from
thunderstorms. On Friday, mostly fair weather conditions are
expected to prevail under a mid-to upper-level ridge building
from the west. This will promote drier air intrusion and
warmer/more stable conditions aloft. However, locally induced
afternoon showers cannot be ruled out over western PR.


&&

.Long Term(Saturday through next Wednesday)...
Issued at 425 AM AST Wed Dec 3 2025

The 250-mb heights are at the 75th percentile of the December
climatology, indicating a strong mid- to upper-level ridge. Model
guidance agrees that this ridge will build and persist over the
Northeast Caribbean, leading to a substantial trade wind inversion
and subsidence caused by a denser, drier air mass located
primarily above 850 mb. Additionally, temperatures at 500 mb are
above normal (warmer than normal), also around the 75th
percentile. At the same time, the low-level lapse rates remain
relatively stable, falling below the 25th percentile and even
below -2 standard deviations. These factors indicate a stable
trend that is expected to dominate the local region over the long
term. Based on this information, both threats, the threat for
thunderstorm formation and flooding rain, were assigned to none
for the long-term period.

Under the described weather pattern, there is a likelihood of
having an advective pattern. As a result, there is a high chance
(60-80%) that residents and visitors in Puerto Rico and the US
Virgin Islands can expect pleasant temperatures, with a mix of
sunshine and clouds each day. However, this advective pattern will
also bring a low (10-20%) to moderate (30-50%) chance of
occasional passing showers, leading to brief periods of moderate
to locally heavy rain in portions of the windward areas of Puerto
Rico and the US Virgin Islands. Additionally, there is a low to
moderate chance of afternoon convection developing across the
interior and western parts of Puerto Rico each day; however,
current forecasts do not indicate a flooding threat at this time.


&&

.AVIATION...
(18Z TAFS)
Issued at 120 PM AST Wed Dec 3 2025

Mainly VFR conds across all TAF sites, with pssbl MVFR conds for IST
and ISX late tnght. -TSRA due aftn convection expcd over interior
and western PR will promote VCTS for JPS and JBQ around 03/18z,
VCSH elsewhere. By 03/23z, winds will become once again lighter
and VRB, increasing around 04/13-14z btwn 6 - 10 kt. PROB30s for
IST and ISX due through producing -TSRA and gsty winds, that may
reduce CIGs/VIS and promote temp MVFR conds.


&&

.MARINE...
Issued at 120 PM AST Wed Dec 3 2025

An east/northeast 4-5 ft swell around 10 seconds and increasing
trades from Thursday onward will promote choppy seas across most
offshore waters and local passages through the weekend. A weak
surface trough will cross the Caribbean waters from tonight
through early Thursday, this will promote mostly light to moderate
winds with a southeasterly component. A building surface high
pressure north of the area will promote moderate to locally fresh
trades(easterlies) once again through early next week.


&&

.BEACH FORECAST...
Issued at 120 PM AST Wed Dec 3 2025

An east to northeasterly swell will promote a moderate risk of
rip currents along the north and east facing beaches of Puerto
Rico, including Vieques and Culebra, and across the U.S. Virgin
Islands. These conditions will persist most of the week due to the
swell and increasing winds from Thursday onward. A moderate risk
means that life-threatening rip currents are possible and can
quickly pull swimmers away from shore.

Even where the risk is lower, rip currents can still form near
groins, jetties, reefs, and piers. Visitors and residents are
strongly encouraged to swim near a lifeguard and remain aware of
changing conditions.

There is a slight risk of thunderstorms, especially during the
afternoon hours, across west Puerto Rico. This activity could
move across coastal areas at times, increasing the risk of
lightning strikes.


&&

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

$$

SHORT TERM...DSR
LONG TERM....MMC
AVIATION...MNG
BEACH/MARINE...DSR

NWS SJU Office Area Forecast Discussion