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630
FXCA62 TJSJ 170729
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
329 AM AST Mon Aug 17 2026

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

.KEY MESSAGES...
Issued at 317 AM AST Mon Aug 17 2026

- An elevated heat threat will persist throughout the workweek
  due to warm temperatures and heat indices above 108 degrees
  Fahrenheit.

- A Heat Advisory is in effect from 10 AM to 5 PM AST for urban
  and coastal areas of Puerto Rico and the U.S. Virgin Islands.

- Dry conditions will persist through late Tuesday, with very
  limited shower activity during the period.

- A tropical wave will approach the local islands by Wednesday
  increasing the potential for showers and thunderstorms.


&&

.Short Term(Today through Wednesday)...
Issued at 317 AM AST Mon Aug 17 2026

Tranquil and generally quiet weather prevailed across the region
overnight, with Doppler radar picking up fast-moving showers over
Caribbean waters while land areas stayed mostly clear. Overnight
lows ranged from the upper 70s to low 80s in coastal and urban
areas, dropping into the 70s across higher elevations. Winds
remained light out of the east at 5 to 10 mph, with land breeze
variations and occasional higher gusts.

An elevated heat risk will affect coastal and urban sections of
Puerto Rico, Culebra, Vieques, and the U.S. Virgin Islands today,
where a Heat Advisory remains in effect from 10:00 AM to 5:00 PM
AST. These conditions significantly increase the risk of heat
exhaustion and heat stroke, especially for young children, the
elderly, and anyone spending extended time outdoors. Stay hydrated,
limit direct sun exposure, and take frequent breaks in the shade or
air conditioning.

Dry, stable air aloft will keep precipitable water (PWAT) values
below normal, between 1.25 and 1.45 inches through Tuesday, limiting
rain chances. Nonetheless, daytime heating and local effects could
trigger isolated showers over western Puerto Rico during the
afternoon. A tropical wave will approach the region from late
Tuesday evening into Wednesday, pulling in deep moisture and driving
PWAT values above-normal values of 2.00 inches. This shift will
sharply increase the potential for widespread showers and
thunderstorms across Puerto Rico and the U.S. Virgin Islands.
Given the ongoing dry spell, any rain will be a welcome relief.
Please continue to monitor the forecast closely throughout the
week for updates as conditions evolve.

&&

.Long Term(Thursday through Monday)...
Issued at 317 AM AST Mon Aug 17 2026

A generally quiet weather pattern is expected through most of the
period, with no significant rainfall hazards anticipated. Moisture
should gradually decrease Thursday into Friday, favoring brief
passing showers and limited afternoon convection over western Puerto
Rico. Heat will likely remain the main concern, with elevated heat
risk possible where sufficient sunshine occurs.

Forecast confidence decreases toward the end of the period as some
guidance suggests an open tropical wave approaching the northeastern
Caribbean by Sunday or the following weekend. At this range,
however, the signal remains highly uncertain and may partly reflect
climatological influences in the model solutions rather than a well-
defined system. Trends will continue to be monitored.

&&

.AVIATION...
(06Z TAFS)
Issued at 317 AM AST Mon Aug 17 2026

Mainly VFR conds expected across all TAF sites. Today, generally
fair weather conditions will prevail across the region with aftn
SHRA across western PR. Light winds btw 5-10 mph through
17/13-14Z. Breezy conditions with occasional gusts up to 26 kt
will persist through 17/23Z. VCSH possible overnight across USVI
sites and TJSJ, but overall no significant impacts expected.

&&

.MARINE...
Issued at 317 AM AST Mon Aug 17 2026

Moderate trade winds will prevail over the region for the next few
days. Expect hazy skies from Saharan dust across the northeastern
Caribbean, with a weak tropical wave bringing increased showers and
possible thunderstorms with gusty winds by midweek. Choppy 6-foot
seas will ease to 3-4 feet later in the workweek.

&&

.BEACH FORECAST...
Issued at 317 AM AST Mon Aug 17 2026

Winds and seas are expected to gradually improve today across the
coastal waters of the islands, and a moderate risk of rip currents
is expected to prevail across the north and east facing beaches of
the islands. A low to moderate risk of rip currents is expected
through most of the workweek as seas subside through midweek.
However, remember that even when the risk is low, life-threatening
rip currents can occur near groins, jetties, reefs, and piers.
Shower and thunderstorm activity could increase on Wednesday with
the arrival of the next tropical wave.

&&

.FIRE WEATHER...
Issued at 317 AM AST Mon Aug 17 2026

Critical fuel conditions persist across the islands, with extreme
drought affecting portions of eastern Puerto Rico and the southern
coastal plains. A drier airmass continues to promote mostly fair
weather across the region while keeping relative humidity levels
below critical thresholds. Combined with ongoing rainfall deficits,
stressed vegetation, and dry fuels, these conditions will favor
rapid fire spread.

The greatest concern remains across southern and southwestern Puerto
Rico, where fuels are exceptionally dry and recent fire activity has
been frequent. However, elevated fire danger extends across all of
Puerto Rico, Vieques, Culebra, and the U.S. Virgin Islands.
Consequently, a Fire Danger Statement is in effect from 10:00 AM to
5:00 PM AST. Residents and visitors are strongly urged to avoid
outdoor burning, as conditions will easily support wildfire ignition
and rapid spread.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk until 6 AM AST early this morning for
     PRZ001>003-005-007-008-011>013.

     Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
     for PRZ001>005-007-008-010>013.

VI...High Rip Current Risk until 6 AM AST early this morning for
     VIZ001-002.

     Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
     for VIZ001-002.

AM...None.
&&

$$

EVENING SHIFT...DSR/ICP
MIDNIGHT SHIFT...GRS

NWS SJU Office Area Forecast Discussion