National Weather Service Today's Weather Impact Levels

823
FXCA62 TJSJ 061643
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
1243 PM AST Sat Dec 6 2025

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

.KEY MESSAGES...
Issued at 1243 PM AST Sat Dec 6 2025

* Mostly fair and stable weather will continue for Puerto Rico, with
  a few quick showers at times, especially overnight and in the
  morning across eastern areas.

* The U.S. Virgin Islands will also see fair weather, with
  occasional brief showers mainly during the night and early morning
  hours.

* Winds will gradually increase by the end of the workweek, leading
  to breezier conditions over the islands and coastal waters.

* A northerly swell expected by the middle and later part of next week,
  combined with increasing winds, may lead to rougher seas and a
  higher risk of life-threatening rip currents, though some
  uncertainty remains regarding its timing and strength.

&&

.Short Term(This evening through Monday)...
Issued at 1243 PM AST Sat Dec 6 2025

Mostly sunny skies have prevailed during the day under a southeast
breeze of 15 to 20 knots. Some showers were observed in the area,
but impacts to land were minimal. The rest of the afternoon will
be fair, with a slight chance of showers for western Puerto Rico
due to diurnal heating. These showers are not expected to lead
into flooding and should be brief in nature.

For tonight, a small perturbation in the trade winds will move in.
This feature will bring near normal moisture levels, hence an
increase in showers will be anticipated for the Virgin Islands and
portions of southern and eastern Puerto Rico. With the enhanced
moisture, showers are expected tomorrow for the Cordillera
Central, western Puerto Rico and portions of the San Juan metro
area. Again, the flooding threat will be very limited, but there
could be some impacts to people enjoying outdoors activities.

Even with the small perturbation moving in, the mid and upper
level atmosphere are dominated by a ridge, maintaining moisture
trapped closer to the surface. Also, a surface high pressure over
the eastern Atlantic will maintain the trade winds coming from the
southeast, at 10 to 20 knots. All these factors work against the
formation of any strong showers.

It will be even drier on Monday, with a drier air mass also
reaching the lower levels of the atmosphere. Any shower that reach
the island will be short lived, limited to portions of the Virgin
Islands and eastern Puerto Rico.

&&

.Long Term(Tuesday through next Friday).../from prev discussion/
Issued at 1243 PM AST Sat Dec 6 2025

A persistent mid-level ridge will dominate the period, maintaining
below- to near-normal mid-level relative humidity and generally
stable conditions. Climatology comparisons keep 700-500 mb relative
humidity in the lower to mid percentiles, but periodic patches of
low-level moisture will still move through, producing brief PWAT
increases and allowing isolated to scattered showers mainly across
eastern PR and the USVI during the nighttime and morning hours.
Afternoon showers over western Puerto Rico remain possible whenever
moisture deepens toward 700 mb. Even with the ridging aloft, 500 mb
temperatures are expected to remain cool enough for seasonal 700-500
mb lapse rates to support limited afternoon convection. Any storms
that develop will be short-lived and shallow, but a few brief
thunderstorms cannot be ruled out.

At the surface, southeast winds start out light early in the period
due to a weak pressure gradient. By the end of the workweek, winds
will strengthen and shift slightly east-southeast as the gradient
tightens across the northeastern Caribbean. Temperatures will remain
above normal, particularly early in the period under a southeasterly
wind flow, supported by 925 mb temperatures and 1000-850 mb
thickness values running near to above normal. Highs will generally
reach the mid to upper 80s at lower elevations.

Overall, the pattern favors stable conditions with passing shallow
moisture, occasional brief convection, increasing winds late in the
workweek, and continued warm temperatures.

&&

.AVIATION...
(18Z TAFS)
Issued at 1243 PM AST Sat Dec 6 2025

Mainly VFR conditions expected to prevail through the forecast
period. Isolated SHRA are observed along the Caribbean and
Atlantic waters, but no impacts to operations are expected. After
06Z, SHRA will increase in the vicinity of the USVI terminals,
and brief periods of reduced VIS and low ceilings can be
anticipated. Winds will be from the ESE at 13-16 kts, with
stronger gusts.

&&


.MARINE...
Issued at 1243 PM AST Sat Dec 6 2025/from prev discussion/

An east to northeast 4 to 5 ft swell at around 10 seconds and
moderate trades will promote choppy seas across most offshore
waters and local passages today. A building surface high pressure
north of the area will maintain moderate to locally fresh trades
(easterlies) on Sunday before subsiding early next week.

&&

.BEACH FORECAST...
Issued at 1243 PM AST Sat Dec 6 2025

Enhanced trade winds will maintain a moderate rip current risk
through mid-week. A northerly swell is expected to reach the
islands by mid-week, that along with breezy conditions should rise
the risk of rip currents to high.

&&

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

$$

SHORT TERM/BEACH/AVIATION...ERG
PUBLIC DESK....GRS

NWS SJU Office Area Forecast Discussion