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102
FXCA62 TJSJ 031832
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
232 PM AST Thu Sep 3 2026

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

.KEY MESSAGES...
Issued at 126 PM AST Thu Sep 3 2026

* Showers and thunderstorms are expected to continue over the
  interior and western portions of PR through the rest of the
  afternoon hours.

* A weak tropical wave will bring an increase in showers and a few
  thunderstorms by early Friday across the USVI and later in the
  day across PR. Ponding of water in poor drainage areas and
  localized minor flooding are possible.

* Hot conditions will continue through the next several days,
  particularly across coastal and urban areas and lower-elevation
  valleys. Dangerous heat conditions are possible this weekend.

* A low risk of rip currents will prevail through the Holiday
  weekend across all beaches of the islands. However, life-
  threatening rip currents can still occur even when the risk is
  low, particularly near groins, jetties, reefs, and piers.

&&

.Short Term(This evening through Saturday)...
Issued at 126 PM AST Thu Sep 3 2026

Brief showers filtered over the eastern region of Puerto Rico during
the morning hours with minimal rainfall accumulations. During the
day temperatures along the coastal areas remained in the upper 80s
to low 90s, while across the mountains they remained in the upper
70s to low 80s degrees Fahrenheits. Heat indices were in general
from the high 90s to the low 100s degrees Fahrenheit along most
coastal and urban areas.

For the rest of this afternoon, expect showers and thunderstorms
to develop due to local effects, daytime heating, and marginal
instability can not be ruled out, especially over interior and
western portions of Puerto Rico during the afternoon hours.
Nevertheless, their effects should remain limited.

On Friday, we anticipate a gradual transition into a slightly wetter
pattern as a weak tropical wave approaches Puerto Rico and the US
Virgin Islands. Model guidance suggests and increase in precipitable
water (PWAT) values up to 2 inches. These conditions may enhance the
development of passing showers and thunderstorms across the US
Virgin Islands and eastern Puerto Rico in the morning hours. In the
afternoon, the humidity along with local effects may favor the
development of showers and thunderstorms over the interior and
western regions of Puerto Rico. However, the effects associated with
these humid conditions will remain limited due to mid-level
stability inhibiting the vertical development for significant
convection. Lingering moisture on Saturday will produce similar conditions
across the islands.

Overall, we forecast limited ponding of water, lightning, and heat
risk throughout the period. During the peak daytime heating, we
recommend limiting outside activities and remaining hydrated. Those
with outdoor plans are encourage to remain vigilant for any weather
updates as the weak tropical waves approaches the region.


&&

.Long Term(Sunday through next Wednesday)...
Issued at 126 PM AST Thu Sep 3 2026

A seasonal weather pattern is expected early next week,
transitioning to drier-than-normal by the end of the period. A
surface high pressure building over the Central Atlantic will likely
maintain E-SE winds throughout most of the period, gradually
strengthening and bringing breezy to windy conditions by the latter
part of the next workweek. Abundant moisture content across the CWA
during the first part of next workweek, particularly on Tuesday into
Wednesday as a tropical wave approaches the Caribbean Basin. Based
on the latest model guidance, PWAT values may vary between seasonal
and above-normal values (between 1.8 and 2.2 inches), with low- to
mid-level moisture content reaching near above climatological normal
(above 60%). In terms of instability, a mid- to high-level ridge
positioned across the region may not favor deeper convection, as mid-
level temperatures seem warmer than normal (between -5 and -6
degrees Celsius) and heights, bringing subsidence and instability
aloft. Nevertheless, the combination of daytime heating, local
effects, and high moisture content should enhance afternoon
convection, with showers and thunderstorms moving over the mountain
ranges into western/northwestern Puerto Rico each afternoon,
increasing flooding threat. Typical showers may move from time to
time across windward sections of Puerto Rico and the U.S. Virgin
Islands.  Rainfall accumulations will likely lead to ponding of
water over roadways and poorly drained areas, with the highest
chance of urban and small stream flooding on Tuesday. Drier-than-
normal conditions can be expected by late Thursday, with PWAT values
plummeting to well below normal for this time of the year (around
1.5 and 1.6 inches), though available moisture and the vicinity of
an upper-level trough weakening the mid-to-high level ridge and
could still enhance afternoon convection.

Due to the moist southeasterly wind flow, above-normal temperatures
are expected during the early part of the long term period, with the
925 mb temperatures above two standard deviations for this time of
the year. Therefore, elevated to significant heat risk is expected
throughout the forecast period, Sunday being the hottest day.

&&

.AVIATION...
(18Z TAFS)
Issued at 126 PM AST Thu Sep 3 2026

Mainly VFR conds are expected to prevail across all terminals
through the fcst period. However, tempo MVFR conds are possible at
TJBQ thru 03/22z due to locally induced SHRA/TSRA. A weak
tropical wave should increase SHRA and iso TSRA from the Anegada
Passage into the USVI/Eastern PR terminals btw 04/10-15z. ESE
winds will continue 10-15 kt with stronger gusts and sea breeze
variations at TJSJ/TJBQ thru at least 03/21z, then becoming light
and variable overnight.

&&

.MARINE...
Issued at 126 PM AST Thu Sep 3 2026

Light to moderate east to southeast winds are expected to prevail
in general through at least early next week. By then,
strengthening of the surface high pressure over the central
Atlantic will promote moderate to fresh trades through the rest of
next week. A weak tropical wave is expected to bring scattered
showers and isolated thunderstorms on Friday, followed by another
tropical wave with an increase in shower and thunderstorm activity
from Sunday into Monday.

&&

.BEACH FORECAST...
Issued at 126 PM AST Thu Sep 3 2026

At least through midweek next week, a low risk of rip currents is
expected to prevail across most beaches, as seas remain between 1
and 3 feet across the coastal waters of the islands. However,
even when the risk for rip currents is low, life-threatening rip
currents often occur in the vicinity of groins, jetties, reefs,
and piers. Beachgoers are encouraged to enjoy generally favorable
beach conditions while remaining aware of isolated rip currents
and changing weather conditions. Afternoon thunderstorms with
cloud to ground lightning are expected each day across the
western coastal areas of Puerto Rico.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.

VI...None.

AM...None.
&&

$$

SHORT TERM...MMC/JCP/RVM/DSR
LONG TERM....MNG/KML
AVIATION/MARINE/BEACH/KEY...DSR

NWS SJU Office Area Forecast Discussion