358
FXCA62 TJSJ 221044 CCA
AFDSJU

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
644 AM AST Mon Dec 22 2025

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

.KEY MESSAGES...
Issued at 530 AM AST Mon Dec 22 2025

* Cloudiness with passing showers, followed by a 50-70 percent
  chance of afternoon showers across western and southwestern
  Puerto Rico. Overnight, passing showers (40-50 percent) are
  expected across the U.S. Virgin Islands and windward Puerto
  Rico, with little to none flooding impacts.

* A break in significant hazardous marine and coastal conditions
  is expected through Tuesday morning. However, conditions are
  forecast to become hazardous again by midweek with the arrival
  of another swell.

* Increasing moisture and an upper-level trough will raise the
  potential for more widespread and heavier rainfall beginning
  Tuesday afternoon into midweek. There is moderate to high
  confidence in periods of locally heavy rain that could lead to
  localized flooding and brief gusty winds.

&&

.Short Term(Today through Wednesday)...
Issued at 530 AM AST Mon Dec 22 2025

Overnight, partly cloudy skies prevailed across the region, with
periods of frequent showers affecting the U.S. Virgin Islands, as
well as northern and eastern Puerto Rico, as a weak induced surface
trough moved through the area. Despite these showers, rainfall
accumulations generally remained below 0.55 inches over land as the
heaviest activity stayed over the waters, limiting flooding impacts.
Overnight temperatures fell into the 60s across higher elevations
and the 70s in urban and coastal areas. Winds were mainly from the
northeast at 6-10 knots, briefly increasing near areas of heavier
shower activity.

Today through Tuesday, there is a moderate to high probability of
partly cloudy conditions during the morning and early afternoon
hours. As daytime heating increases, there is a 50-70 percent
chance of shower development across western and southwestern
Puerto Rico, which could result in brief periods of moderate
rainfall and localized ponding of water. During the overnight
hours, passing showers are likely (40-50 percent) across the U.S.
Virgin Islands and windward sections of Puerto Rico, with
generally minor flooding impacts.

Moisture levels are expected to temporarily increase to near or
slightly above normal on Tuesday afternoon as a frontal boundary
approaches from the Atlantic waters. At the same time, an upper-
level trough will introduce colder-than-normal temperatures near the
500 mb level through midweek. This pattern increases the potential
for deep and unstable rainfall activity particularly heading into
midweek. There is a moderate to high confidence. The primary impacts
during this period would include localized flooding and brief gusty
winds.

&&

.Long Term(Thursday through Monday)...
Issued at 530 AM AST Mon Dec 22 2025

Current model guidance suggest precipitable water (PWAT) values
of around 1.4 inches to start the period. A series of mid to upper
level troughs will move north of the region through the Friday,
while a cold front approaches and likely moves over the region on
Thursday (Christmas Day). Although they start an upward trend,
instability is evident as 500 mb temperatures will still be below
normal on Thursday at -10 to -8 degrees Celsius. A limited
flooding risk will be present for most of the region, as the
frontal boundary moves over the region, resulting in showers and
possible isolated t-storms under north-northeast steering flow.
Model guidance has been fairly consistent with each run regarding
the approach of these features. With uncertainty remaining in the
exact impacts across Puerto Rico and the U.S. Virgin Islands. As
drier air behind the front will promote improved weather
conditions with a cooling trend continuing Friday through Monday,
925 mb temperatures are forecast to be below normal for this
period. Lows are forecast in the 50s to low 60s across higher
elevations of PR, in the upper 60s to mid 70s across lower
elevations of PR, and in the low to mid 70s across the USVI. Highs
are forecast in the around the mid 80s across lower elevations of
the islands, with isolated/urban areas a bit higher. Although
PWAT values are forecast at around to below an inch, isolated
patches of moisture will reach the area and promote passing
showers from time to time.

&&

.AVIATION...
(06Z TAFS)
Issued at 530 AM AST Mon Dec 22 2025

VFR conditions are expected to prevail across most terminals through
the period. However, SHRA may intermittently affect TJSJ, TIST, and
TISX, especially during the overnight and early morning hours. TJPS
could experience VCSH after 1217Z. Winds will remain from the NE at
6-10 knots, with occasional higher gusts near passing showers.

&&

.MARINE...
Issued at 530 AM AST Mon Dec 22 2025

A building surface high over the western Atlantic and a frontal low
over the north-central Atlantic, will promote east to northeast winds
to start the period. A series of surface highs and frontal lows will
continue moving into the Atlantic during the period, resulting in
moderate to locally fresh east to northeast winds through at least
Wednesday, when they back to become more north-northeasterly. A
fading northeasterly swell will promote seas up to 6 feet for the
offshore Atlantic Waters today. Marine conditions will continue
briefly improving tonight into early Tuesday. A northerly long-period
swell, from one of the above mentioned frontal lows, will once again
result in hazardous marine conditions for small craft at the
offshore Atlantic Waters by Tuesday afternoon. Hazardous conditions
will continue through the workweek as seas build to 6 to 9 feet and
spread to the nearshore Atlantic Waters and local Passages.


&&

.BEACH FORECAST...
Issued at 530 AM AST Mon Dec 22 2025

A fading northeasterly swell will result in mostly a moderate
risk of rip currents to start the workweek, across the northern
and eastern coastline of Puerto Rico, Culebra and Vieques, as well
as for beaches of the USVI. Coastal conditions will continue
gradually improving through Tuesday night; however, another
northerly long-period swell will increase the risk up to high
again by Wednesday through probably the rest of the week. Please
continue to monitor the forecast for updates as conditions evolve.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...Small Craft Advisory from noon Tuesday to midnight AST Thursday
     night for AMZ711.

&&

$$

SHORT TERM/AVIATION...MMC
LONG TERM/MARINE/BEACH FORECAST...MRR

NWS SJU Office Area Forecast Discussion