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109
FXCA62 TJSJ 011835
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
235 PM AST Sun Feb 1 2026

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

.KEY MESSAGES...
Issued at 219 PM AST Sun Feb 1 2026

* An elevated flood threat continues through midweek. Periods of
  moderate to heavy rainfall may result in urban and small stream
  flooding, localized flash flooding, and minor landslides,
  especially across steep terrain. The risk increases late tonight
  through Tuesday. Residents and visitors should remain alert and
  avoid rivers, creeks, and flood-prone areas.

* While swell energy has temporarily diminished today, a strong
  north to northwesterly long-period swell will arrive Monday,
  producing very hazardous marine and coastal conditions. High
  Surf and High Rip Current Risk conditions are likely, with beach
  erosion and minor coastal flooding possible in vulnerable
  coastal areas.

* Marine conditions will deteriorate rapidly beginning Monday as
  increasing winds and building seas impact local waters. Small
  Craft Advisories are in effect, with additional marine zones
  likely to be added as hazardous seas develop.

* Isolated to scattered thunderstorms will continue through at least
  midweek, capable of producing frequent lightning, brief gusty
  winds, heavy rainfall, and reduced visibility over land and
  coastal waters.

* The U.S. Virgin Islands will remain on the drier side of the
  system this afternoon; however, shower coverage will increase
  late tonight and Monday, with the highest rainfall potential
  expected Monday night through Tuesday.

&&

.Short Term(This evening through Tuesday)...
Issued at 219 PM AST Sun Feb 1 2026

Throughout the day, periods of sunny to partly cloudy skies and
generally calm conditions prevailed across Puerto Rico and the U.S.
Virgin Islands. A band of showers associated with a frontal boundary
remained northwest of the region, extending across the western
Atlantic waters and the Mona Passage. Non-official weather stations
reported temperatures along the coastal areas in the upper 80s to
low 90s, while temperatures across the higher terrain ranged from
the upper 70s to low 80s. Winds were mainly from the south to
southeast.

Tonight, rain chances will increase as the frontal boundary
approaches the region, with the greatest impacts expected across
western and northwestern Puerto Rico. As a result, the risk of
flooding will rise across these areas tonight and remain elevated
through at least midweek. Across the U.S. Virgin Islands, shower
activity will be more prevalent during the morning hours.

From Monday into Tuesday, under a north to northeast low-level flow,
shower and isolated thunderstorm activity will shift toward
southern, southeastern, and eastern Puerto Rico, with some activity
spreading into the San Juan metropolitan area. Periods of moderate
to heavy rainfall will remain possible across the islands under
continued moist and unstable conditions.

Overall, a wet and unsettled weather pattern is expected to persist
across the region through at least Tuesday. This pattern is being
driven by an approaching frontal boundary from the northwest, an
upper-level polar trough, and a mid- to upper-level ridge positioned
east of the islands. This synoptic setup will maintain a favorable
environment for deep-layer instability and efficient rainfall,
supported by persistent moisture transport from the Caribbean and
precipitable water values remaining well above normal for this time
of year, near or exceeding 2.25 inches. As the frontal boundary
approaches and crosses the region, winds will gradually shift from
southerly to northwesterly by the beginning of the workweek. Given
this setup, the flooding risk will remain elevated across much of
the region through Tuesday, with the potential for significant
flooding, particularly across southern and eastern Puerto Rico.
Expected impacts include rapid river rises, urban and small-stream
flooding, potentially life-threatening flash floods, landslides in
steep terrain, and locally gusty winds. Residents and visitors are
urged to closely monitor weather updates and remain alert to
changing conditions.

&&

.Long Term(Wednesday through next Saturday)...
Issued at 448 AM AST Sun Feb 1 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. This will slow and turn
winds more easterly, and keep an overall higher moisture content
over the area, particularly on Wednesday. Also, a short-wave
trough will promote colder than normal 500 mb temperatures around
minus 7/8C, which destabilizes the atmosphere and increase once
again the likelihood of thunderstorms. Therefore, another
unsettled weather day is expected across the islands, and due to
the expected saturated soils, any additional period of excessive
rainfall will lead to quick flooding. Lingering moisture and
small variations on the 500 mb temperatures will promote shower
and isolated thunderstorm development once again on Thursday.
However, a drying trend is now expected on Friday and early
Saturday, before the arrival of the next deep polar trough and
associated frontal boundary during the weekend.

&&

.AVIATION...
(18Z TAFS)
Issued at 219 PM AST Sun Feb 1 2026

Mainly VFR conditions are expected to prevail across all TAF sites
through the fcst pd. However, SHRA will affect portions of Puerto
Rico and the U.S. Virgin Islands, resulting in brief periods of MVFR
conditions at times. The greatest potential for MVFR conditions will
be across TJPS, then shifting to TJBQ, TJSJ, TIST, and TISX after
approximately 02/00Z. Isolated TSRA cannot be ruled out tonight into
Monday, which may temporarily reduce visibility and ceilings.

&&

.MARINE...
Issued at 219 PM AST Sun Feb 1 2026

Moderate southerly winds will continue through this afternoon ahead
of an approaching frontal boundary. Winds will shift to the west and
north late tonight into Monday as the front moves through the
regional waters.

In the wake of the front, winds are expected to increase
significantly, with sustained speeds of 20 to 25 knots and higher
gusts through at least Tuesday. A strong north-northwesterly long-
period swell will build into the local waters beginning Monday,
resulting in very hazardous marine conditions, particularly across
the Atlantic waters and passages. Seas are expected to build to 8 to
12 feet, with higher seas possible in exposed waters.

Scattered to numerous showers and isolated thunderstorms will
continue across the regional waters, with thunderstorms capable of
producing locally gusty winds, rough seas, and reduced visibility.

Small Craft Advisories are in effect beginning Monday morning, with
additional marine zones likely to be added as conditions continue to
deteriorate through midweek.

&&

.BEACH FORECAST...
Issued at 219 PM AST Sun Feb 1 2026

Nearshore buoy observations indicate that northerly swell energy has
diminished somewhat today, resulting in slightly reduced surf
heights compared to earlier this morning. Despite this temporary
decrease, hazardous marine and beach conditions persist, and a high
risk of rip currents continues across all north-facing beaches.

Beginning Monday, a strong north-northwesterly long-period swell
will build into the region and persist through at least midweek.
This swell will result in rapidly increasing surf heights, powerful
breaking waves, and very dangerous coastal conditions, especially
along exposed Atlantic and northwestern coastlines. Peak impacts are
expected Monday into Tuesday.

As a result, High Surf Advisories are very likely, along with a
continued High Rip Current Risk. In addition, coastal flooding of
low-lying and vulnerable shoreline areas is possible, and a Coastal
Flood Advisory may be required as onshore flow and elevated tides
combine.

Beachgoers should also remain alert for nearby thunderstorms, which
may produce locally gusty winds, lightning, and sudden reductions in
visibility, further increasing the risk for marine and beach
activities. Beachgoers and mariners are urged to continue monitoring
forecast updates and heed all local advisories, warnings, and
guidance from lifeguards and local officials as conditions
deteriorate.

For localized and updated rip current information, visit
weather.gov/beach/sju.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk until 6 PM AST this evening for PRZ001-002-
     005-008-010-012.

VI...High Rip Current Risk until 6 PM AST this evening for VIZ001.

AM...Small Craft Advisory from 6 AM Monday to 2 AM AST Thursday for
     AMZ711-712-741-742-745.

&&

$$

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

NWS SJU Office Area Forecast Discussion