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377
FXCA62 TJSJ 281850 CCA
AFDSJU

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
250 PM AST Thu Aug 28 2025

.KEY MESSAGES...

* The US Virgin Islands and Puerto Rico are expected to
  experience above-normal heat indices for the remainder of today
  and tomorrow afternoon, with a moderate to high chance of
  issuing an Extreme Heat Warning or Heat Advisory.

* A tropical wave will promote a limited to elevated risk of flooding
  rain during the afternoon today and tomorrow, especially across
  the interior and western PR and St Croix.

* We expect a low risk of rip currents throughout the Labor Day
  weekend.

* We expect passing showers to arrive across the windward
  locations of PR and the USVI, followed by afternoon convection
  across western PR each day.

&&

.SHORT TERM...Tonight through Sunday

Hot heat indices prevailed across some urban and coastal sections
of PR and the USVI throughout the morning and afternoon hours.
However, the proximity of a tropical wave contributed to the
formation of showers and thunderstorms across the eastern third of
PR, portions of the USVI, and surrounding waters late in the
morning into the afternoon. Additionally, afternoon thunderstorms
developed along the north coast in PR, where frequent lightning,
torrential rainfall, and gusty winds occurred across portions of
the islands. Winds were mainly from the east- southeast at 10 to
20 mph, with variations due to sea breezes.

Showers and thunderstorms will develop along PR`s northern half
through this evening, and some locations will have a limited to
elevated chance of flooding rain. However, locations without rain
will experience extreme heat; thus, the Extreme Heat Warning and
Heat Advisory will continue in effect for PR and the USVI through
5 PM AST. The above-normal ocean sea surface temperature will
enhance the formation of scattered to numerous showers across the
local waters, moving inland over the windward locations of PR and
the USVI. A similar weather pattern is expected to prevail
tomorrow (Friday), with excessive heating during the day, followed
by strong afternoon convection.

We expect a mixture of sunshine and clouds on Saturday, with a
typical hydrological pattern consisting of passing showers across
the windward locations, followed by afternoon convection across
western PR and downwind from the US Virgin Islands.

The risk of rip currents will remain moderate tonight along the
north-facing beaches of PR and the US Virgin Islands.
Thunderstorms could also impact the northwest quadrant of PR
through this evening. The risk of rip currents is expected to
decrease to low from Friday onward. However, isolated stronger rip
currents may occur elsewhere, especially near piers, jetties, and
channels.

.LONG TERM...Sunday through Thursday...

From Sunday through midweek, the overall weather pattern will
resemble typical seasonal conditions. A steady easterly wind flow
will transport patches of trade wind moisture across the islands
from time to time. This will favor brief overnight and early
morning showers across the U.S. Virgin Islands and eastern Puerto
Rico, followed by afternoon convection over the interior and
western portions of Puerto Rico due to sea breeze convergence and
diurnal heating. Localized heavy downpours, occasional lightning,
and ponding of water will be possible with the afternoon activity.

By Thursday, a surface perturbation is forecast to approach the region,
enhancing available moisture and instability. This will increase
the potential for more widespread showers and thunderstorms.

Overall, the long-term forecast highlights a seasonally typical
pattern through midweek, transitioning to slightly wetter and
unstable conditions late in the period as the perturbation
approaches.

Heat advisories remain possible from Sunday through Thursday, as model
guidance indicates 925 mb temperature and humidity values ranging
from the 75th percentile to greater than two standard deviations
above normal during the period.


&&

.AVIATION...
(18Z TAFs)

Mainly VFR conditions across most TAF sites with the exception of
TJBQ that have TSRA and VCTS. As a result MVFR to intermittent IFR
likely through at least 28/22-23Z. Sfc winds bcmg light and variable
after 28/23Z. VCSH possible during the overnight period across USVI
TAF sites, TJSJ and TJBQ. After 29/14Z, E to SE winds at 10 to 12
kts with sea breeze typical variations followed by VCTS and TSRA
after 29/17Z at TJBQ.

&&

.MARINE...

The trailing moisture from a tropical wave, moving near PR and the
USVI will promote showers and thunderstorms this afternoon and
tomorrow. Another weak tropical wave will enter the Lesser
Antilles by Saturday. Mariners can expect moderate east to east-
southeast winds and moderate chops across the regional waters the
rest of the weekend into early next week.

&&

.BEACH FORECAST...

The risk of rip currents will remain moderate tonight along the
north-facing beaches of PR and the US Virgin Islands.
Thunderstorms could also impact the northwest quadrant of PR
through this evening. The risk of rip currents is expected to
decrease to low from Friday onward. However, isolated stronger rip
currents may occur elsewhere, especially near piers, jetties, and
channels.

&&
.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Extreme Heat Warning until 5 PM AST this afternoon for
     PRZ001>005-007-008-010-011.

     Heat Advisory until 5 PM AST this afternoon for PRZ012-013.

VI...Heat Advisory until 5 PM AST this afternoon for VIZ001-002.

AM...None.
&&

$$

SHORT TERM...CAM
LONG TERM....YZR
AVIATION...99

NWS SJU Office Area Forecast Discussion