720
FXCA62 TJSJ 270844
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
444 AM AST Sat Dec 27 2025

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

.KEY MESSAGES...
Issued at 500 AM AST Sat Dec 27 2025

*  Pulses of long-period northerly swell will maintain hazardous marine
   conditions today, especially across Atlantic waters and local
   Caribbean passages. Current and additional swell pulses will
   also sustain a life-threatening rip current risk along north-
   facing beaches of Puerto Rico, Culebra, and the northern U.S.
   Virgin Islands through at least Sunday. High surf risks will
   persist through this afternoon at exposed shores. While
   conditions may gradually improve thereafter, additional swell
   pulses early next week may once again deteriorate marine and
   beach conditions.

* Overall weather conditions will remain mostly quiet, with brief passing
  showers at times and little to no thunderstorm activity
  expected. A slight increase in shower activity and a low chance
  of isolated thunderstorms is possible mid- to late week as a
  short-wave trough and a weak surface-induced trough approach the
  region, though impacts are expected to remain localized.

* U.S. Virgin Islands: Weather conditions will remain generally
  stable, with passing showers at times and no thunderstorm
  potential, even during the midweek period. No significant inland
  weather impacts are anticipated.

* New Years Eve: Showers may become more frequent, especially
  across western Puerto Rico, with a low chance of isolated
  lightning. Forecast confidence is moderate, as model guidance
  continues to fluctuate.

&&

.Short Term (Today through Monday)...
Issued at 500 AM AST Sat Dec 27 2025

Clear skies were observed across Puerto Rico and the Virgin Islands
during the night hours. It was very cool too, with some stations
reporting lows in the upper 50s at higher elevations, and the mid
60s to low 70s elsewhere.

Satellite-derived precipitable water imagery show very dry air
across the region, with values of only 0.75 inches, which is well
below the normal value for this time of year. At the surface, high
pressure is centered over the western Caribbean, and a polar trough
is covering most of the Atlantic Ocean. This is causing a weak
steering flow across the local islands, coming out of the northeast
today at 4 to 7 kts, less than 4 knots tomorrow, and from the east
at 5 to 7 kts on Monday. Also, the high will maintain very low
relative humidities at the mid levels, with a trade wind cap
inversion at 850 mb. Under these conditions, heavy showers are not
expected to develop, but local effects may still trigger some
showers along the interior and western Puerto Rico. Impacts are
expected to be very limited, possibly with ponding of water and wet
roads.

Temperatures will remain very comfortable too, with 925 mb values at
one to two standard deviations below normal. For mountains: expect
lows in the 50s and 60s, and highs in the low 70s. For low
elevations and coastal areas: expect lows in the 60s and low 70s,
and highs in the low 80s.


&&

.Long Term (Tuesday through Saturday)...
Issued at 419 AM AST Sat Dec 27 2025

From Tuesday through Thursday, a dry and stable winter pattern
will dominate, supported by post-frontal dry air pushing southward
and weak mid-level ridging. This will favor mostly fair weather,
limited shower activity, and cooler nighttime temperatures typical
for this time of year. During this same period, an eastward-moving
surface high north of the region will mainly influence the wind
pattern, maintaining a gentle to moderate east-southeast breeze
through Thursday.

A slight transition is expected later in the period as a short-
wave trough approaches from the west. Although the latest guidance
indicates its axis will remain west of the islands, it will still
influence the region by weakening the mid-level ridge and
supporting the development of a weak surface trough late Friday
into Saturday. This setup may allow moisture to shift back toward
the area, with the highest sensitivity across western Puerto Rico
and the Mona Passage, while other areas experience more limited
effects.

From Wednesday night into Saturday, showers may become more
frequent in favored areas, especially across western and interior
Puerto Rico and exposed coastal locations, with a few periods of
locally heavy rainfall possible. A low chance of isolated
thunderstorms exists late Friday into early Saturday, mainly over
western Puerto Rico and nearby waters, producing brief heavy rain,
gusty winds, and lightning. Winds are expected to weaken and
become more variable late Friday into Saturday due to the surface
trough, which may support a warmer-than-normal feel on Friday,
particularly during the afternoon. Forecast confidence is
moderate, as moisture fields continue to shift and guidance
oscillates between wetter and drier solutions. This variability is
not necessarily negative, as New Years Eve currently trends
drier with generally favorable conditions, though marine and beach
hazards may continue.


&&

.AVIATION...
(06Z TAFS)
Issued at 500 AM AST Sat Dec 27 2025

VFR conditions expected to prevail through the forecast period. SHRA
is expected after 17Z for TJPS, with brief periods of reduced VIS
and low ceilings. After 22Z, VCSH are expected for TJSJ and USVI
terminals, but impacts are expected to be limited. Winds will be
from the ENE from 5-9 kts, becoming light and variable after 22Z.


&&

.MARINE...
Issued at 500 AM AST Sat Dec 27 2025

A surface high pressure system over the western Atlantic will
maintain light to moderate east to northeast winds across the
local waters over the next few days. Meanwhile, pulses of long-
period northerly swell will continue to spread into the region,
maintaining hazardous marine conditions. Small Craft Advisories
remain in effect through this afternoon, with rough seas
persisting afterward as the swell gradually diminishes. Looking
ahead, additional pulses of northerly swell are expected early
next week, which may bring another round of hazardous conditions
for small craft across the local waters.


&&

.BEACH FORECAST...
Issued at 500 AM AST Sat Dec 27 2025

A High Rip Current Risk remains in effect through tonight along
north-facing beaches of Puerto Rico, Culebra, St. Thomas, and St.
John, while a High Surf Advisory remains in effect through 6 PM
this evening for the north coast of Puerto Rico. Recent buoy
observations (NE Puerto Rico buoy 41043) confirm additional pulses
of long-period northerly swell, bringing seas of 78 feet with
periods of 1213 seconds across the local Atlantic waters and
Caribbean passages. These conditions support the potential for
breaking waves exceeding 10 feet at exposed beaches, reinforcing
dangerous and life-threatening swimming conditions today.

Beachgoers are strongly urged to stay out of the water at north-
facing beaches, especially at unguarded locations, and to follow
all beach flag warnings and coastal advisories. For additional
details and the latest updates, refer to the Coastal Hazard
Message (CFWSJU).


&&

.FIRE WEATHER...
Issued at 500 AM AST Sat Dec 27 2025

Drying conditions continue to develop, especially across southern
Puerto Rico, where localized abnormally dry conditions persist. Monthly
rainfall has been minimal, and 30- to 60-day rainfall deficits
continue, supporting the ongoing drying of fine fuels.

There is no elevated fire danger today. While there is some
uncertainty in drought and soil moisture indices, KBDI values have
increased to around 540 at Cabo Rojo and 503 at Camp Santiago,
indicating increasing fuel dryness, though still below thresholds
for Fire Weather Statement or Red Flag Warning. Low relative
humidity at times, combined with occasional wind gusts of 2025
mph typical of winter trade-wind patterns, has briefly enhanced
fire spread potential, with a few small wildfires observed.
Overall, fire danger remains low at present, but continued drying
over the next several days to weeks could elevate fire risk,
warranting close monitoring, particularly across southern Puerto
Rico.


&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through late Sunday night for PRZ001-002-
     005-008-010-012.

     High Surf Advisory until 6 PM AST this evening for PRZ001-002-
     005-008-010.

VI...High Rip Current Risk through late Sunday night for VIZ001.

AM...Small Craft Advisory until 6 PM AST this evening for AMZ711-712-
     716-723-741-742.

&&

$$

SHORT TERM/AVIATION...ERG
LONG TERM....ICP

NWS SJU Office Area Forecast Discussion