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225
FXCA62 TJSJ 311844
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
244 PM AST Sat Jan 31 2026

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

.KEY MESSAGES...
Issued at 228 PM AST Sat Jan 31 2026

* The flood risk will persist through midweek. Urban and small
  stream flooding, localized flash flooding, and minor landslides
  in areas of steep terrain are possible, particularly from late
  Sunday through Tuesday. Residents and visitors are urged to
  avoid small streams, creeks, and other recreational areas near
  rivers.

* Life-threatening rip currents are expected today across the
  northern beaches from Rincon to Fajardo, Culebra and the
  northern USVI. A large, long-period northerly swell and
  increasing winds will bring hazardous seas and life-threatening
  rip currents across most waters and coastal areas of the islands
  from Monday onward. Rough surf and life-threatening rip currents
  are expected. Beach erosion and minor coastal flooding are
  likely in the most vulnerable coastal areas.

* Isolated thunderstorms are possible from the weekend into early
  next week, bringing localized lightning and brief gusty winds.

* Across the USVI, sunny to partly cloudy skies are expected this
  morning, followed by an increase in cloudiness and shower
  activity from this afternoon through the rest of the weekend.

&&

.Short Term(This evening through Monday)...
Issued at 228 PM AST Sat Jan 31 2026

Across Puerto Rico and the U.S. Virgin Islands, overall
cloudy skies and humid conditions prevailed throughout the day.
During the morning hours, showers affected Saint Croix and southern
portions of Puerto Rico. By the early afternoon, shower activity
shifted across the interior and eastern sections of Puerto Rico,
with additional rain bands filtering over southern Puerto Rico from
the Caribbean waters later in the afternoon. Through 230 PM AST,
radar estimates and non-official surface observations indicated
rainfall accumulations ranging from approximately 1.0 to 1.6
inches. Despite persistent cloud cover and passing showers,
temperatures remained in the upper 80s along coastal areas, while
cooler readings in the 70s were observed across the interior.

The 31/12Z sounding depicts moist low levels with a dry layer
between 700-500 mb; however, this dry mid-level air is already
eroding, as shown by the GOES satellite imagery, which indicates
mid- level moisture lifting over the region. This supports
continued top- down moistening of the column through the period.
Precipitable water values will increase to well above normal
levels, locally approaching two standard deviations above
climatological normal.

The synoptic pattern is characterized by a polar trough at upper
levels and an associated frontal boundary northwest of the region,
along with a deep-layer ridge to the east, maintaining persistent
southerly low-level flow today and Sunday. This southerly flow
will favor the clustering of showers and isolated thunderstorms
across southern portions of Puerto Rico and potentially the
southern U.S. Virgin Islands through Sunday, supported by enhanced
low-level moisture convergence. Upper- level support remains
modest but sufficient to sustain periods of showers, with locally
heavier activity possible where convergence persists. Late Sunday
night into early Monday, a col ahead of the approaching frontal
boundary is expected to move across the region, resulting in a
temporary decrease in wind speeds.

By Monday, low-level winds are expected to increase again and veer
more northerly as the frontal boundary approaches and moves over the
area. This change in the low-level flow will favor a northward shift
in shower and isolated thunderstorm activity, with increasing
coverage across northern portions of the CWA. ECMWF Extreme Forecast
Index guidance supports this evolution, with EFI values increasing
from modest levels today to higher values on Sunday and peaking on
Monday, reflecting increased ensemble weighting toward the wettest
solutions.

Potential impacts through the period include ponding of water on
roadways, urban and poor-drainage flooding, localized small-stream
rises, and reduced visibility in heavier showers. Gusty winds may
accompany stronger showers or isolated thunderstorms. Overall, the
short-term period is expected to remain unsettled, with the primary
concerns being above-normal rainfall and localized flooding
potential, particularly from Sunday into Monday.

&&

.Long Term(Tuesday through next Friday)...
Issued at 240 AM AST Sat Jan 31 2026

The frontal boundary is expected to linger near the local area
through midweek, as a weak area of high pressure rolls from the
western Atlantic and passes just north of the area into the
central Atlantic by the end of the workweek. A series of deep-
layer lows/troughs will continue to move from the western into the
north-central Atlantic, promoting colder than normal 500 mb
temperatures and favorable conditions for thunderstorm development
on Wednesday and Thursday. Another approaching front is expected
to reach the local area once again by Saturday. These weather
features will keep higher than normal moisture content over the
islands, and a wet and unsettled weather period is expected to
prevail through the long-term period. Therefore, if the expected
weather in the short-term period materializes, any additional
excessive period of heavy rainfall over saturated soils will lead
to quick flooding and possible minor landslides in areas of steep
terrain.

Breezy northeasterly winds will prevail through Wednesday, turning
more east to southeasterly from Thursday onward, and becoming
light and variable on Saturday as the front moves closer to the
region.

&&

.AVIATION...
(18Z TAFS)
Issued at 228 PM AST Sat Jan 31 2026

Mainly VFR conds exp across all TAF sites thru the fcst pd. SCT -
SHRA/+SHRA will cont to affect PR/USVI, with brief MVFR/IFR CIGs/VIS
psbl at times, particularly southern terminals. Isold TSRA could
increase on Sun. S-SE sfc winds 10-15 kt with ocnl higher gusts,
weakening aft 31/23z, then incrg again aft 01/13Z.

&&

.MARINE...
Issued at 228 PM AST Sat Jan 31 2026

A Small Craft Advisory remains in effect for the offshore Atlantic
waters as seas continue to reach up to 7 feet. Winds and seas are
expected to gradually subside on Sunday. However, by early Monday
morning, a large, long-period northerly swell is forecast to
arrive, causing seas to build up to around 12 feet and persist
through at least midweek. Additionally, an unsettled weather
pattern will result in more frequent showers and isolated
thunderstorms, which may locally enhance winds and seas, creating
hazardous marine conditions and further exacerbating existing
hazards., particularly from Sunday onwards.

&&

.BEACH FORECAST...
Issued at 228 PM AST Sat Jan 31 2026

The lingering northerly swell will continue to promote a high
risk of rip currents through 6 AM tomorrow across all northern-
facing beaches, including areas from Rincon to Fajardo, Culebra,
and the northern U.S. Virgin Islands.

Beginning Monday, a stronger, long-period northerly to north-
northwesterly swell is forecast to arrive and persist through the
workweek. This swell is expected to once again elevate the rip
current risk to high, while also increasing the potential for high
surf and minor coastal flooding, particularly during the peak of the
event from Monday into Tuesday across exposed Atlantic and
northwestern coastlines. Beachgoers are urged to continue monitoring
future forecasts as conditions evolve.
&&

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

VI...High Rip Current Risk through late tonight for VIZ001.

AM...Small Craft Advisory until 6 AM AST Sunday for AMZ711.

&&

$$

SHORT TERM/AVIATION...CVB
LONG TERM...DS
MARINE/BEACH...MMC

NWS SJU Office Area Forecast Discussion