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758
FXCA62 TJSJ 071713 AAA
AFDSJU

Area Forecast Discussion...UPDATED
National Weather Service San Juan PR
113 PM AST Fri Aug 7 2026

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

.KEY MESSAGES...
Issued at 1244 PM AST Fri Aug 7 2026

- Warm to hot conditions will continue this weekend and early
  next week across the islands, particularly over urban and low-
  lying areas. The Heat Advisory remains in effect through 5:00 PM
  AST.

- Moderate concentrations of Saharan Dust will reach the local
  area tomorrow, with very high concentrations on Sunday and
  Monday. Sensitive groups must follow medical recommendations.

- A drier and more stable weather pattern will persist through
  the weekend. Limited rainfall is expected, allowing drought
  conditions to continue worsening across Puerto Rico and the U.S.
  Virgin Islands.

- Elevated fire weather conditions may persist for the next few
  days across southern and southwestern Puerto Rico due to
  critically dry fuels, low relative humidity, and breezy
  conditions.

&&

.Short Term(This evening through Sunday)...
Issued at 1244 PM AST Fri Aug 7 2026

Sufficient lower-level moisture, combined with strong daytime
heating and sea breeze convergence, will trigger diurnally induced
afternoon showers across portions of the islands today. The
heaviest showers with isolated thunderstorms will focus across the
interior and western Puerto Rico, where ponding of water on roads
or minor flooding is possible. In contrast, the U.S. Virgin
Islands and eastern Puerto Rico will stay mostly sunny to partly
cloudy with only brief, isolated showers. Maximum temperatures
should reach the lower 90s across most coastal areas. The wind
will prevail from the east to northeast around 15 mph.

A drying trend is expected into Saturday as a dense layer of
Saharan dust moves over the northeastern Caribbean. Satellite
observations and aerosol tracking indicate that the peak in
density of the event will be from late Saturday into Sunday,
causing a drop in moisture content to near or below 1 inch by
early Saturday morning. This dense, dry air mass will create
strong sinking air that prevents clouds and shower activity from
building up. As a result, fair but particularly hazy skies will
dominate the entire region through the end of the weekend, with
rainfall remaining minimal across Puerto Rico and the U.S. Virgin
Islands. However, a weak tropical wave is forecast to track just
south of the area on Sunday, and guidance suggests a bump in
precipitable water to near normal levels. Regardless, this should
favor shower development again, mainly over western PR in the
afternoon hours. At the same time, the rest of the area could see
a slight increase in passing morning/evening showers.

With limited cloud cover and plenty of sunshine, temperatures will
climb rapidly each afternoon, and due to the expected hazy
conditions, warmer than normal minimum temperatures are possible.
Therefore, warm to hot conditions are expected to prevail during
the weekend. In addition, the dust event will reduce air quality,
making outdoor activities hazardous for sensitive groups with
respiratory conditions.

&&

.Long Term(Monday through next Thursday)...
Issued at 1244 PM AST Fri Aug 7 2026

For the long-term period, a warm pattern is forecast through the
first part of the period. The 12Z NASA GEOS-5 aerosol optical depth
(AOD) guidance indicates a dense Saharan Air Layer (SAL) plume
dominating the northeastern Caribbean early in the period. This high
concentration of Saharan dust will promote strong radiative heating
and warmer overnight temperatures. As a result, above-normal minimum
and maximum temperatures will persist, particularly across coastal
and urban areas. Meanwhile, an upper-level high pressure centered
near 250 mb and extending across the eastern Caribbean will promote
cirrus advection and periods of high-level cloudiness across the
area on Monday. Therefore, residents are urged to stay tuned for
possible heat-related alerts. Conditions will remain fairly similar
through Tuesday morning, with warm temperatures continuing across
the area but with lower concentrations of Saharan dust. A rapid
change in the weather pattern is expected by Tuesday afternoon as
surface high pressure strengthens north of the region. The resulting
tight pressure gradient will induce a strong low-level easterly wind
surge, promoting breezy to windy conditions across the local islands
and surrounding waters.

Another pattern transition is expected by midweek as the axis of an
easterly tropical wave approaches the local area on Wednesday,
increasing column moisture and pushing precipitable water (PWAT)
values toward 2.0 inches. According to the latest global model
guidance, the peak in moisture is expected between Wednesday
afternoon and Thursday morning. Depending on the extent of cloud
cover and early-day convective activity, sufficient insolation
combined with the moist boundary layer could make Wednesday the
warmest day of the period. Nevertheless, local diurnal heating and
sea-breeze convergence will promote afternoon convection,
particularly across interior and western Puerto Rico. The tropical
wave will maintain elevated low-level moisture into Thursday;
however, forecast confidence regarding rainfall intensity and
coverage remains low, as a drier air mass behind the wave axis could
quickly move into the region and limit organized convection. By
Friday, a more typical trade-wind pattern is expected to return,
with lingering low-level moisture supporting brief passing showers
across windward areas. Overall, above-normal temperatures and
periods of elevated to significant heat risk are expected to persist
through much of the extended period.

&&

.AVIATION...
(18Z TAFS)
Issued at 1244 PM AST Fri Aug 7 2026

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hours. However, locally induced SHRA may cause
brief MVFR cigs at TJPS thru 07/22z. Elsewhere, mostly VCSH
expected. The 07/12z TJSJ sounding indicated ENE winds up to 20 kt
blo FL080.

&&

.MARINE...
Issued at 1244 PM AST Fri Aug 7 2026

A broad surface high building over the western Atlantic will
maintain moderate east-to-northeasterly winds for the rest of the
afternoon, becoming moderate to locally fresh, as winds continue to
strengthen tonight. Building seas up to 6 feet may lead to choppy
conditions across the regional waters and local passages. Afternoon
thunderstorms near western coastal waters of Puerto Rico may produce
gusty winds and locally hazardous conditions for small craft. A
dense layer of Saharan Dust will gradually filter into the region on
Saturday, with hazy skies, reduced visibility, and poor air quality
through at least Tuesday.

&&

.BEACH FORECAST...
Issued at 1244 PM AST Fri Aug 7 2026

No changes were introduced to the beach forecast. The moderate risk
of rip currents continues across northern and eastern beaches of
Puerto Rico, including Vieques and Culebra, and the U.S. Virgin
Islands; low elsewhere. Although the risk is moderate, beachgoers
must exercise caution as life-threatening rip currents remain
possible along the surf zone. As winds continue to gradually
strengthen this weekend, the moderate risk may spread across most
beaches of Puerto Rico and the U.S. Virgin Islands. Besides rip
currents, beachgoers visiting beaches in the western side of Puerto
Rico should remain alert as isolated thunderstorms could move near
the coastal areas and produce gusty winds and lightning. Moderate to
very high concentrations of Saharan Dust will move across the region
this weekend and early next week, bringing hazy skies and reduced
visibility.

&&

.FIRE WEATHER...
Issued at 1244 PM AST Fri Aug 7 2026

Critical fuel conditions persist across the islands, with extreme
drought conditions across portions of the southern coastal plains of
Puerto Rico. RAWS stations have reported winds between 8 - 13 mph
and gusts up to 25 mph during the morning hours. Additionally, as a
drier air mass continues to filter into the region, moisture content
has dropped significantly, with RH values between 47 and 54 %, well
below thresholds. Due to critical fuel conditions across the
southern area of the island and KDBI values well above thresholds,
the fire danger threat remains elevated. Hence, the Fire Danger
Statement continues in effect through 5 PM AST. Residents and
visitors are encouraged to avoid outdoor burning, as conditions will
likely be favorable for wildfire ignition and rapid spread.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory until 5 PM AST this afternoon for PRZ001>005-007-
     008-010>013.

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

AM...None.
&&

$$

KEY/MARINE/BEACH/FIRE...MNG
AVIATION/SHORT TERM...DSR
LONG TERM....LIS

NWS SJU Office Area Forecast Discussion