611
FXCA62 TJSJ 240752 CCA
AFDSJU

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
301 AM AST Fri Jul 24 2026

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

.KEY MESSAGES...
Updated at 251 AM AST Fri Jul 24 2026

 * A weak tropical wave will increase briefly shower activity
   today across portions of the islands, but mainly over western
   PR in the afternoon.

 * Breezy and hazy conditions will prevail through Saturday.

 * A more vigorous tropical wave is forecast from late Sunday into
   Monday, increasing the potential for showers and flooding.

 * There is a moderate risk of rip currents across locally
   exposed beaches for the rest of the workweek into the weekend.

&&

.Short Term(Today through Sunday)...
Issued at 251 AM AST Fri Jul 24 2026

A building surface high over the central Atlantic will promote
breezy easterlies across the northeastern Caribbean through the
end of the week. Recent satellite imagery and aerosol models
indicate that a dense Saharan Air Layer continues to encompass the
region today, bringing significant dust concentrations over the
islands. This dry and highly stable air mass will limit widespread
precipitation, promoting hazy skies and degraded air quality
through early Saturday. For today, a weak tropical wave will
briefly bump moisture content to be sufficient to combine with
daytime heating and orographic effects to trigger isolated
afternoon convection over the interior and western municipalities
of Puerto Rico.

Fluctuations in moisture content and dust concentrations will
continue on Saturday, and outside of the afternoon convective
activity in western Puerto Rico, passing nighttime and early
morning trade wind showers will remain the primary source of light
precipitation for the U.S. Virgin Islands and the eastern third of
Puerto Rico. Warm to hot conditions are anticipated through most
of the short-term period with elevated heat indices (100-108F) in
the lower elevations before the onset of  afternoon showers and
in rain-free areas. Vulnerable populations should exercise
caution, as these hot conditions could reach heat advisory
criteria across portions of the coastal and urban areas of PR.

A notable transition is expected by late Sunday, as the latest
global model guidance and forecast soundings show another tropical
wave introducing a much deeper pool of moisture to the islands.
Precipitable water values are forecast to surge from below normal
to near the 75th percentile by then. This moisture bump will
weaken the stable mid-level cap, significantly increasing the
coverage and intensity of showers and isolated thunderstorms. As a
result, motorists and residents should expect an enhanced threat
for localized urban and small stream flooding by Sunday afternoon
across all islands.

&&

.Long Term(Monday through Friday)...
Issued at 251 AM AST Fri Jul 24 2026

Current model guidance suggests a wetter pattern at the beginning of
next work week. The combination of a tropical wave and an upper-
level low will bring increased chances of rain. As the tropical wave
moves across the region, PWAT values are expected to increase to
above-normal levels through at least Tuesday, exceeding 2 inches,
which is around the 75th percentile for this time of year. Aloft, an
upper-level low positioned over the islands through Monday will
maintain lower 250-mb heights and cooler 500-mb temperatures (around
-8 to -9C), with both remaining near to below seasonal normals.
This pattern will increase the potential for thunderstorm
development. Moisture will also increase in the mid and upper
levels, creating a more unstable environment across the islands. As
a result, Monday is expected to be the day with better dynamics for
the development of showers and thunderstorms. Additionally, winds
are forecast to remain very light that day, resulting in slow-moving
showers and thunderstorms capable of producing higher rainfall
accumulations. As a result, the flood threat will remain elevated on
Monday across the interior and western portions of Puerto Rico, with
the potential for flooding in urban areas, along roads, in small
streams, and in washes. A more limited flood threat is expected
across eastern Puerto Rico and the USVI.

By Tuesday and Wednesday, the upper-level low will shift slightly
west of the area, allowing some stability aloft, as reflected by
rising heights and temperatures. At the same time, Atlantic high
pressure will gradually strengthen, causing easterly to
southeasterly winds to increase and become breezy to locally windy.
However, moisture content will remain above average and, when
combined with local effects and diurnal heating, will likely support
overnight and morning windward showers, followed by afternoon
convection across the interior and western portions of Puerto Rico.
The flood threat during these days is currently expected to be more
limited and mainly confined to northwestern Puerto Rico, with
ponding of water on roads and in poorly drained areas being the
primary concern. This forecast will continue to be refined with each
update as confidence increases.

Drier air will begin filtering into the area from Wednesday night/
Thursday through Friday, accompanied by some Saharan dust. As PWAT
values decrease to near seasonal levels, isolated trade wind showers
will continue due to the presence of patches of moisture embedded in
the trades, but overall shower coverage is expected to be more
limited than during the previous days. Throughout most of the
forecast period, available moisture and southeasterly wind flow,
particularly from Wednesday onward, will maintain warm to hot
conditions, resulting in an elevated heat risk across coastal and
urban areas.

&&

.AVIATION...
(06Z TAFS)
Issued at 251 AM AST Fri Jul 24 2026

Mainly VFR conds expected to prevail across all terminals.
However, SHRA/-TSRA expected to develop in and around TJBQ btw
24/18-22z, which may lead to tempo MVFR conds. Elsewhere, mostly
VCSH expected. HZ due to Saharan dust will continue to increase
late today and VSBY may drop to 6SM. Low-level winds from the east
at 14-18 kt with sea breeze variations and stronger gusts aft
24/13z

&&

.MARINE...
Issued at 251 AM AST Fri Jul 24 2026

A broad surface high pressure will maintain moderate to locally
fresh winds through at least Saturday. Winds will remain from the
east-southeast today, becoming from the east later tonight. Moderate
concentrations of Saharan dust will continue to linger across the
region throughout the weekend, with slight reductions in visibility.
A weak tropical wave is forecast to move across the region today,
however, widespread shower activity is not anticipated. A vigorous
tropical wave is expected to reach the northeastern Caribbean from
late Sunday into Monday, increasing moisture and the potential for
thunderstorm activity over the local Caribbean waters, which will
result in localized hazardous marine conditions.

&&

.BEACH FORECAST...
Issued at 251 AM AST Fri Jul 24 2026

A moderate risk of rip currents is expected across the northern and
eastern exposed beaches of Puerto Rico, Culebra, Vieques and St.
Croix. Life-threatening rip currents are possible, and beachgoers
should exercise caution and swim near a lifeguard whenever possible.
A low risk is expected elsewhere. Low to moderate concentrations of
Saharan dust will result in hazy conditions through at least
Saturday. A weak tropical wave will cross the region today, followed
by a more vigorous tropical wave expected Sunday into Monday. As a
result, showers and isolated thunderstorms are likely across the
regional waters, posing a lightning risk at area beaches.

&&

.FIRE WEATHER...
Issued at 251 AM AST Fri Jul 24 2026

A dusty, drier air mass is expected to move later today, along
with the passage of a brief and weak tropical wave. Increasing
winds are expected along the southern coastal plains, and overall
drier conditions are expected there, which could support fire
weather conditions.

&&

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

$$

SHORT TERM...DSR
LONG TERM....YZR
AVIATION/FIRE...DSR
BEACH/MARINE...GRS