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138
FXCA62 TJSJ 291750
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
150 PM AST Mon Dec 29 2025

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

.KEY MESSAGES...
Issued at 115 PM AST Mon Dec 29 2025

* Life-threatening rip currents will continue to prevail across
  the north-facing beaches of Puerto Rico, Culebra, and the
  northern U.S. Virgin Islands through Tuesday. The rip current
  risk is expected to decrease to moderate by midweek as the
  swell action subsides.

* The risk of lightning and localized flooding will increase from
  New Years Eve through the end of the week.

&&

.Short Term(This afternoon through Wednesday)...
Issued at 115 PM AST Mon Dec 29 2025

Mostly sunny skies prevailed across the forecast area today, with
minimal rainfall activity observed. Maximum temperatures ranged
from the upper 70s to the mid 80s under light northeast winds.

Heights are forecast to fall toward the end of the period as a
mid to upper level trough moves across the western tropical
Atlantic into the central Caribbean. At lower levels, northeast
winds will persist through tonight, shifting to the east southeast
by Tuesday afternoon into Wednesday as the aforementioned trough
and its associated frontal boundary approach from the west. This
evolving pattern will promote moisture pooling across the region,
with precipitable water values exceeding climatological values on
Wednesday.

Meanwhile, tonight and Tuesday, limited shower activity is
expected to continue, supported by precipitable water values below
1.0 inch and the absence of significant upper level forcing. As
a result, isolated to locally scattered passing showers are
expected overnight into Tuesday morning across the north and east
coastal areas of Puerto Rico, as well as the northern U.S. Virgin
Islands, followed by limited convection over the western interior
of Puerto Rico on Tuesday afternoon. Shower and thunderstorm
coverage is expected to increase on Wednesday, potentially
elevating the risk of lightning and localized flooding.

&&

.LONG TERM...(Thursday through Monday)...
Issued at 420 AM AST Mon Dec 29 2025

A shortwave trough is expected to swing across the Northeast
Caribbean by Thursday (New Year`s Day), followed by an amplifying
mid- to upper-level trough over the region through Friday. This
pattern will promote increased instability and a more unsettled
weather regime, especially as a frontal boundary and associated pre-
frontal trough approach the area late Thursday night into Friday. At
the surface, a high-pressure system over the central Atlantic will
maintain an east to east-southeast low-level wind flow through early
next week.

The most favorable window for widespread rainfall appears to be
between Thursday afternoon and Friday evening. However, model
guidance continues to show timing discrepancies regarding both the
onset and departure of the most active period. Rainfall could begin
as early as early Thursday morning and linger into early Saturday
morning. At this time, the highest confidence for widespread shower
activity is from Thursday afternoon into Friday, when periods of
moderate to heavy rain and thunderstorms are most likely. Another
negative factor for the formation of widespread activity could be
the available moisture over the region, where we observed another
discrepancy in the model guidance.

By Saturday, the region will transition to the subsident side of the
mid- to upper-level trough as it lifts eastward, with subsidence
gradually increasing. This will result in a decreasing trend in
shower and thunderstorm coverage and intensity through the weekend.
Although passing showers will remain possible Saturday into Sunday,
vertical development will be limited as a mid- to upper-level ridge
builds over the area.

Late Sunday night into Monday, another shortwave trough is forecast
to approach the region, increasing mid- to upper-level instability.
This may lead to a gradual uptick in shower activity, with the
trough aloft expected to further amplify by Monday night into
Tuesday, potentially signaling a return to more unsettled conditions
early next week.

&&

.AVIATION...
(18Z TAFS)

Mainly VFR conds across all TAF sites, with VCSH for IST for the
rest of the aftn, then for JSJ later tonight, reducing CIGs. Winds
from the NE will become light and VRB after 29/22z, increasing
from the E btwn 6 - 11 kt by 30/13-14z.

&&

.MARINE...
Issued at 115 PM AST Mon Dec 29 2025

A northeast wind flow will continue to prevail across the local
waters through midweek, gradually veering to the east and east-
southeast as a frontal boundary approaches from the west,
increasing the potential for showers and thunderstorms. Pulses
of long-period northerly swell will persist across the Atlantic
waters and Caribbean passages through the middle of the week.

&&

.BEACH FORECAST...
Issued at 115 PM AST Mon Dec 29 2025

A long period northerly swell will continue to prevail across the
local waters, maintaining a high risk of life threatening rip
currents along the north-facing beaches of Puerto Rico, Culebra,
and the northern U.S. Virgin Islands through at least Tuesday
afternoon. The rip current risk is expected to decrease to
moderate on Wednesday as swell action gradually subsides.
Nevertheless, beachgoers are urged to exercise caution at
all times.

&&

.FIRE WEATHER...
Issued at 420 AM AST Mon Dec 29 2025

Drying conditions continue, especially across southern Puerto
Rico, where minimum relative humidity has fallen below 40% for a
second consecutive day, with some locations dropping into the 20s
to 30s. Winds remain light, limiting fire spread at this time.
KBDI values continue to increase, with Cabo Rojo exceeding fire
danger thresholds (above 550) and Camp Santiago approaching
similar levels, indicating increasingly dry fuels. While no
significant fire weather threat is expected today, continued
drying through mid to late week warrants close monitoring,
particularly as stronger winds are possible Friday into Saturday,
which could elevate fire spread potential if dry conditions
persist.

&&

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

VI...High Rip Current Risk through Tuesday afternoon for VIZ001.

AM...None.
&&

$$

SHORT TERM...OMS
LONG TERM/FIRE...MIDNIGHT CREW
AVIATION...MNG

NWS SJU Office Area Forecast Discussion