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191
FXCA62 TJSJ 090610
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
210 AM AST Thu Jul 9 2026

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

.KEY MESSAGES...
Issued at 210 AM AST Thu Jul 9 2026

* The greatest potential for showers and isolated thunderstorms
  will occur today, mainly across western Puerto Rico. Another
  increase in tropical moisture is expected early next week.

* While warm to hot conditions will persist, the greatest heat
  impacts are expected today, with another period of dangerous
  heat possible early next week.

* Fire danger will increase today and peak Friday into the weekend.

* Breezy to windy easterly trade winds will persist, with the
  strongest winds expected today through the weekend.

* Moderate to locally high concentrations of Saharan dust will
  peak today, then gradually diminish through the weekend.


&&

.Short Term(Today through Saturday)...
Issued at 210 AM AST Thu Jul 9 2026

A weak tropical wave will continue to move across the eastern
Caribbean today. However, with its deepest tropical moisture
remaining well south of the local islands, a drier-than-normal
weather pattern accompanied by increasing Saharan dust will become
established through the remainder of the period. As rainfall
coverage diminishes, the primary weather concerns will transition
to dangerous heat, elevated to critical fire danger, breezy to
windy easterly trade winds, and hazy skies with occasional
reductions in visibility and air quality.

The passage of the wave will provide sufficient low-level moisture
to support isolated to scattered showers and perhaps an isolated
thunderstorm across western Puerto Rico this afternoon, although
the overall flooding and lightning threats will remain limited and
very localized. At the same time, mid- and upper-level conditions
will become less favorable for organized convection, allowing
sunshine and daytime heating to become the primary weather
drivers. Combined with hot temperatures, lingering humidity,
breezy easterly winds, and only limited overnight relief, these
conditions will support elevated to locally extreme heat,
especially across the lower elevations, coastal areas, and urban
locations of Puerto Rico. As a result, a Heat Advisory has been
issued for portions of the forecast area. Meanwhile, strengthening
winds, increasing Saharan dust, and a progressively drier air
mass will promote elevated fire danger. By tonight, both the
1000-700 mb and 0-3 km layer relative humidity decrease
considerably as the drier-than-normal air mass becomes firmly
established over the region.

Friday through Saturday, moderate to locally high concentrations
of Saharan dust, progressively drier air, and generally stable
conditions will dominate the local weather pattern. Expect hazy
skies, isolated passing trade-wind showers, and only brief
afternoon convection across western Puerto Rico. Breezy to windy
easterly trade winds will persist under a strong North Atlantic
surface high, while hot days and warm nights continue to provide
little relief from the heat. Elevated fire danger will also
persist. Refer to the Fire Weather discussion below for additional
details.


&&

.Long Term(Sunday through Thursday)...
Issued at 210 AM AST Thu Jul 9 2026

Theres more agreement in the global model solutions regarding early
next weeks weather pattern. A series of surface high pressures will
maintain E-ESE winds throughout the forecast period, with breezy to
locally windy conditions across coastal areas of the islands.
Moderate concentrations of Saharan Dust will likely linger on
Sunday, limiting any shower activity, but will gradually diminish
and remain low in the evening. As mentioned in the previous
discussion, model guidance suggested the approach of a tropical wave
into the Caribbean Basin, but they differed in the time of arrival.
From the latest solution, both GFS and ECMWF suggest that moisture
content will increase across the CWA by late night Sunday into
Monday, with 850 - 700 mb values ranging between 50 and 70 %. In
terms of instability, the proximity of an upper-level low northeast
of the CWA may introduce slight instability across the area, as
model guidance indicates cool mid-level temperatures (around -8
degrees Celsius) on Sunday and Monday. With the presence of low
concentrations of Saharan Dust, thunderstorm development, if any,
may be enhanced, increasing lightning potential. Hence, the highest
chance of shower and thunderstorm activity can be expected on
Monday, affecting mainly windward sections of the islands in the
morning, followed by afternoon convection over interior and western
Puerto Rico. Rainfall accumulations may lead to  ponding of water
over roadways and poorly drained areas, along with minor flooding.
Based on the latest NASA GEOS-5 Dust AOT, Saharan Dust
concentrations should increase from Tuesday onwards, resulting in
hazy skies, reduced visibility, and poor air quality, with limited
shower activity. Sensitive groups must follow medical
recommendations.

Seasonal to near-above-normal temperatures are expected in the
forecast period, and combined with available moisture, heat indices
will likely exceed 100 degrees Fahrenheit mainly over urban and low-
lying areas of the islands. As mentioned in previous discussions,
the presence of Saharan Dust may inhibit nighttime cooling, with
warmer minimum temperatures. Therefore, the heat threat will likely
remain limited to elevated throughout the forecast period.


&&

.AVIATION...
(06Z TAFS)
Issued at 210 AM AST Thu Jul 9 2026

VCSH expected at TJSJ/TIST/TISX through 10/12-14Z as a weak
tropical wave moves across the eastern Caribbean. SHRA possible
near TJBQ 10/17-21Z, with a low chance of an ISOLD TSRA over far W
PR. Otherwise, VFR with HZ at all TAF sites. E-ESE sfc winds 20-25
kt with gusts 30-35 kt through 10/22Z, diminishing thereafter.


&&

.MARINE...
Issued at 210 AM AST Thu Jul 9 2026

A broad surface high pressure over the central Atlantic will promote
moderate to fresh east to east-southeast winds, and choppy to
hazardous seas through the end of the workweek. The arrival of a
strong Saharan Air Layer, and a passing tropical wave to our south
will bring fresh to strong (20-25 kt) winds today across most local
waters. Scattered showers are expected with this wind surge, mainly
across the Caribbean waters. Moderate to high concentrations of
Saharan dust will continue to produce hazy skies and reduced
visibilities. Small craft advisories are in effect through late
Friday, due to a combination of 7 ft seas and 20 to 25 kt easterlies
across both Atlantic and Caribbean waters, including the Mona
Passage.


&&

.BEACH FORECAST...
Issued at 210 AM AST Thu Jul 9 2026

Wind-driven seas and breezy conditions will maintain a moderate risk
of rip currents across most beaches of Puerto Rico and the U.S.
Virgin Islands through the rest of the week and into the weekend.
This means that life-threatening rip currents will remain possible
in the surf zone. Beachgoers are encouraged to remain cautious.
Additional beach hazards include the presence of Saharan dust, which
will result in hazy skies, reduced air quality, and warm to hot
conditions during the peak heating hours of the day. An elevated
heat threat will persist on most days, with heat indices ranging
from 100F to 110F across most coastal areas, particularly along
the northern, western, and southern coastlines of Puerto Rico.


&&

.FIRE WEATHER...
Issued at 210 AM AST Thu Jul 9 2026

Localized heavy rainfall over the past several days has done
little to improve the broader fire weather concerns across
southern and eastern Puerto Rico, Vieques, St. Croix, and adjacent
areas, where persistent rainfall deficits, critically dry fuels,
and elevated KBDI values continue. A progressively drier-than-
normal air mass moving into the region today, moderate to locally
high concentrations of Saharan dust, and breezy to windy easterly
trade winds will support increasingly favorable conditions for
wildfire spread through the weekend, with the greatest fire danger
expected Friday into the weekend. A Fire Danger Statement has been
issued for portions of southern Puerto Rico today, and additional
fire weather products may be needed over the next several days if
dry and windy conditions persist.


&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
     for PRZ001>005-007-008-010-011.

     Fire Danger Statement from 10 AM this morning to 4 PM AST this
     afternoon for PRZ014-015-018-019-022-024-027.

VI...None.
AM...Small Craft Advisory until midnight AST Friday night for AMZ711-
     733-741.

     Small Craft Advisory from noon today to 6 AM AST Friday for
     AMZ712-735.

&&

$$

EVE...DSR/MNG
MID...ICP

NWS SJU Office Area Forecast Discussion