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705
FXCA62 TJSJ 010728
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
328 AM AST Sun Nov 1 2026

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

.KEY MESSAGES...
Issued at 247 AM AST Sun Nov 1 2026

 * Passing showers will move in across the islands this morning,
   followed by stronger showers and thunderstorms for the interior
   and west of Puerto Rico.

*  Warmer than normal heat indices will persist through the
   workweek, so stay hydrated and take plenty of breaks when
   outdoors.

*  A moderate rip current risk will persist through the workweek
   for the north facing beaches of Puerto Rico and Culebra.

&&

.Short Term(Today through Tuesday)...
Issued at 247 AM AST Sun Nov 1 2026

A few thunderstorms moved through the local waters through the
night hours, but rainfall over land was very limited.
Skies were mostly cloudy, and temperatures dropped to the mid 70s
to low 80s in coastal areas, and in the mid 60s across the
Cordillera Central.

For today, high pressure will continue to drive the trade winds
from the east-southeast, but winds will be a little stronger,
around 13 kts. Under this flow, drier air will be advected today.
However, there is enough moisture to generate afternoon showers
and thunderstorms across the interior and western Puerto Rico.
Rainfall accumulations should be less than what was experienced
yesterday. A similar pattern is expected on Monday, with
a drier air mass filtering from 850 to 500 mb. The winds will be a
little stronger as well. Low level moisture should carry passing
showers into the region.

By Tuesday, conditions are expected to change. First, the wind
flow will become mostly from the south, from the surface into the
mid levels of the atmosphere. This will cause temperatures to
soar, with even higher heat indices anticipated. Also, the
probability of precipitation will increase, mostly after the
evening hours, as significant moisture is lifted from the
Caribbean.


&&

.Long Term(Wednesday through Sunday)...
Issued at 247 AM AST Sun Nov 1 2026

A generally warm and humid weather pattern is expected across Puerto
Rico during the long term period. Precipitable water (PWAT) values
are expected to remain generally elevated most of the forecast
period, ranging between 1.9 and 2.3 inches. Low-level relative
humidity (850 to 700 mb) is expected to remain generally between 70%
and 85%, while mid-level moisture (700 to 500 mb) will increase
considerably from Wednesday through Friday, reaching values near or
above the 75th climatological percentile of the month of November.
Some drying is then anticipated toward the end of the period,
particularly on Sunday, as drier air filters into the region.
Meanwhile, 500 mb temperatures around -5 to -6C will contribute to
some atmospheric instability, particularly during periods of
stronger daytime heating. At the synoptic level, an upper-level low,
along with its associated surface low and frontal boundary, will
move northward across the Atlantic waters during the period. This
evolution will favor southerly low-level winds, allowing tropical
moisture to be transported toward the region, particularly on
Saturday as the system moves farther north. Light winds will
generally prevail across the local area, contributing to weak
steering flow and potentially slow moving showers.

A warm and humid air mass will remain in place on Wednesday, with
elevated moisture supporting widespread shower development,
particularly across the interior and western portions of the island.
Combined with daytime heating, sea breeze convergence, and
orographic lifting, periods of heavy rainfall are possible. Light
winds will result in weak steering flow, allowing showers to move
slowly and increasing rainfall accumulations, with localized urban
and small stream flooding possible. Wednesday is currently expected
to be one of the wettest days of the period.

Somewhat drier air is forecast to filter into the mid and upper
levels on Thursday and Friday, resulting in a slight decrease in
available moisture and shower activity. Nevertheless, light winds,
daytime heating, and local effects will continue to support
afternoon showers, particularly across interior and western Puerto
Rico. The overall flooding threat should decrease slightly during
these days, although isolated heavy rainfall cannot be ruled out.
Moisture is expected to increase again on Saturday as southerly to
southwesterly winds transport additional tropical moisture into the
region pulled by the low and frontal boundary moving across the
Atlantic, north of Puerto Rico and USVI. This could make Saturday
another one of the wettest days of the long term period, favoring
shower and thunderstorm development. Light winds will still
contribute to weak steering flow and potentially slow moving
showers. Consequently, locally heavy rainfall could lead to
increased accumulations and localized flooding.

By Sunday, drier air is expected to reach the region, favoring a
decrease in available moisture and overall shower activity. Although
isolated to scattered afternoon showers may still develop across the
interior and western sections due to daytime heating and local
effects, rainfall coverage and intensity should generally decrease.
Continue to monitor the forecast as confidence increases and updated
model guidance becomes available.

&&

.AVIATION...
(06Z TAFS)
Issued at 247 AM AST Sun Nov 1 2026

Mainly VFR conditions expected this morning. SCT SHRA and TSRA
expected across the local waters, occasionally reaching the
terminals. After 17Z, organized convection is expected for the
Cordillera Central. Periods of reduces VIS and low ceilings are
expected for TJPS and TJBQ. Winds will be from the ESE at 12-14
kts, with stronger gusts.

&&

.MARINE...
Issued at 247 AM AST Sun Nov 1 2026

A frontal boundary over the western Atlantic will remain north of
the local waters and gradually weaken through early next week. The
associated surface pressure pattern will support a generally
easterly wind flow across the regional waters. Passing showers and
isolated thunderstorms are possible, with locally higher winds and
seas near thunderstorms. The wind and wave guidance suggests that
seas may increase somewhat early next week as east to east-southeast
winds strengthen Monday and Tuesday. Mariners should monitor the
latest coastal waters forecast for updates on winds and seas.

&&

.BEACH FORECAST...
Issued at 247 AM AST Sun Nov 1 2026

A moderate risk of rip currents is expected across many north and
east facing beaches of Puerto Rico and the U.S. Virgin Islands
through much of the forecast period. Beachgoers should exercise
caution and check the latest beach forecast before entering the
water. Isolated thunderstorms may also affect beaches, particularly
during the afternoon. If you hear thunder, leave the beach and seek
shelter in a substantial building or enclosed vehicle.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

SHORT TERM/AVIATION...ERG
LONG TERM....YZR
MARINE/BEACH...CAM

NWS SJU Office Area Forecast Discussion