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510
FXCA62 TJSJ 121800
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
200 PM AST Sat Jul 12 2025

.KEY MESSAGES...

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* Moderate concentrations of Saharan dust particles will continue
  to limit rain chances and promote hazy skies, reduced visibilities
  and poor air quality across Puerto Rico and the U.S.Virgin
  Islands through Sunday early afternoon hours.

* Mainly low risk of rip currents Sunday and Monday. By Tuesday,
  increasing winds will result in a moderate risk of rip currents
  to return across most local beaches.

* A tropical wave will approach the islands by the middle of the
  week, increasing moisture and the potential to observe showers
  and thunderstorms.
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&&

.SHORT TERM...
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Tonight through Monday...

Partly cloudy and hazy skies prevailed this morning across Puerto
Rico and the U.S. Virgin Islands, with mainly rain-free conditions.
Daytime temperatures have reached the upper 80s to low 90s across
urban and coastal areas of the islands, while remaining in the low
80s across the higher elevations. Surface weather stations have
registered heat index values ranging from the upper 90s to 109
degrees Fahrenheit, and a Heat Advisory remains in effect until 5
PM AST this afternoon for the urban areas and lower elevations of
Puerto Rico. Residents and visitors are encouraged to stay hydrated,
avoid outdoor activity during peak heat, wear light clothing, and
check on vulnerable people and pets.

For the rest of today, the latest models suggest the development of
diurnally induced isolated to scattered showers across the western
sectors of Puerto Rico; however, if any occur, no significant
rainfall accumulations are expected. A lingering Saharan Air Layer
(SAL) with moderate concentrations will continue to promote hazy
skies and poor air quality across the islands through at least
midday tomorrow.

The rest of the period remains largely on track. A TUTT-low north of
the area will gradually move westward, enhancing diurnally induced
afternoon shower activity over western Puerto Rico again tomorrow
(Sunday). However, precipitable water content is expected to remain
below normal (below 1.50 inches). As a result, showers will remain
very localized in western Puerto Rico, driven by local effects, and
the flood risk will likely remain from none to limited. Early next
week, a trade wind perturbation will approach the region, increasing
PWAT values to around 1.6 inches and improving chances for more
widespread shower activity across the islands.

.LONG TERM...Tuesday through Saturday...
.PREV DISCUSSION... /issued 438 AM AST Sat Jul 12 2025/

A trade wind perturbation is expected to arrive into the area on
Tuesday, increasing moisture into the area and the potential to
observe shower activity across the islands. The forecast have not
changed a lot with the previous model guidance, and continues to
suggest the arrival of a broad tropical wave by mid-week. The latest
precipitable water content analysis suggest values up to 2.10 inches
by Wednesday afternoon. Therefore, showers and thunderstorms are
likely over portions of central, western and eastern Puerto Rico,
and the U.S. Virgin Islands  from Wednesday morning through the
evening hours. This fast moving wave is expected to exit the region
by late Wednesday, followed by a atmospheric perturbation on
Thursday.

By the end of the workweek, a drier air mass accompanied by another
pulse of Saharan Air layer is anticipated to arrive into the area by
Thursday, following the atmospheric perturbation passage over the
region. This event will limit the shower activity across the
islands and will promote hazy skies, reduced visibilities and
deteriorated air quality throughout the area until the weekend.

Hot temperatures will continue across the region next week. Maximum
temperatures are expected to remain in the upper 80s to low 90s
along the coastal and urban areas, and around the mid 80s in the
higher elevations. Heat indices could reach values above 105 degrees
Fahrenheit each day, particularly over the northern, western and
southern municipalities of Puerto Rico. Residents and visitors,
please be aware of these conditions and plan accordingly if planning
to do outdoor activities under sun exposure.
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&&

.AVIATION...
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(18Z TAFs)

Expect VFR conditions across all terminals during the next 24 hours.
Hazy skies and visibilities between 6 and 9 SM will continue thru at
least tomorrow early afternoon due to a SAL. A few occasional trade
wind SHRA/-SHRA will affect the local islands, without ruling out a
few over the TAFs. Expect winds from the E/ENE at 15-20 kt with
higher gusts and sea breeze, bcmg calm to light/VRB aft 12/23z.
Expect a similar weather and wind pattern tomorrow, but with an
increase in SHRA/TSRA during the aft 13/17z.
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&&

.MARINE...

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A surface high pressure across the central Atlantic will continue
to promote moderate easterly winds across the region. Seas will
range from 2 to 4 feet across the onshore waters and local
passages, and from 3 to 5 feet across the offshore waters.
Moderate concentrations of Saharan dust will linger through early
Sunday afternoon, promoting hazy skies, reduced visibility, and
deteriorated air quality. Moderate to fresh easterly winds are
expected to return by early next week, and small craft operators
will likely be encouraged to exercise caution. A tropical wave
will approach the islands by the middle of next week, increasing
moisture and the potential to observe some showers and
thunderstorms.
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&&

.BEACH FORECAST...

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A moderate risk of life-threatening rip currents will likely persist
tonight and Sunday across the northern beaches of Puerto Rico. A low
risk is expected elsewhere; however, life-threatening rip currents
may still occur, especially near groins, jetties, reefs, and piers.
Always swim near a lifeguard and follow the advice of local beach
patrols and flag warning systems.

Starting Tuesday, a moderate risk of rip currents is anticipated to
return to most beaches, accompanied by increasing winds. Warm and
hazy conditions are expected to persist through the weekend, with
heat index values likely exceeding 100F. Stay well hydrated, seek
shade frequently, and avoid outdoor activity during peak sun hours.
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&&

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

VI...None.
AM...None.
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&&

$$

SHORT TERM/MARINE/BEACH FORECAST...YZR
LONG TERM...GRS
AVIATION...CAM