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318
FXCA62 TJSJ 131824
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
224 PM AST Mon Jul 13 2026

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

.KEY MESSAGES...
Issued at 156 PM AST Mon Jul 13 2026

- A drier airmass along with moderate to high concentrations of
  Saharan dust will continue to spread across the region,
  promoting hazy skies, reduced visibilities, poor air quality and
  limited shower activity. Sensitive groups, particularly those
  with respiratory issues or allergies, should take necessary
  precautions to limit outdoor exposure.

- Breezy easterly winds will persist through much of the week.
  While winds are expected to be slightly weaker than last week,
  they will continue to produce choppy marine conditions and
  hazardous conditions for small craft at times.

- A moderate risk of rip currents continues across several local
  beaches. Life-threatening rip currents remain possible,
  especially near piers, jetties, and sandbars.

&&

.Short Term(This evening through Wednesday)...
Issued at 156 PM AST Mon Jul 13 2026

This morning, some passing showers were observed across winds ward
areas of the islands, but overall quiet fair weather conditions and
hazy skies have prevailed. The 12Z TJSJ sounding measured 1.88
inches of precipitable water (PWAT), which is in the 50th percentile
for this time of year. GOES satellite imagery also suggested similar
values this morning, but values are already decreasing as drier air
is pushing into the area. Values are around 1.60 inches and are
expected to follow a decreasing trend over the short term period.
Surface observations have registered gusts up to 25-30 mph near
coastal areas. Afternoon temperatures across urban and lower-
elevation areas have climbed into the upper 80s and low 90s,
producing heat indices generally low 100s, with some urban locations
exceeding 105-108 F. A Heat Advisory remains in effect through 5 PM
AST.

A strengthening surface high over the central Atlantic will tighten
the local pressure gradient from Tuesday through Wednesday,
resulting in locally breezy easterly winds across the islands. At
the same time, a drier air mass accompanied by moderate to high
concentrations of Saharan dust will continue to spread across the
region, promoting stable weather conditions but hazy skies and
reduced air quality. Consequently, rainfall activity will remain
limited through the short term period, with the best chance for
isolated afternoon showers (if any) confined to the western interior
of Puerto Rico as local effects interact with daytime heating.
Rainfall probabilities are generally expected to remain low.

The combination of abundant sunshine, limited cloud cover, and warm
easterly flow will favor above-normal temperatures. Daytime highs
are expected to reach the 90s across coastal and urban areas during
the early afternoon hours. Overnight temperatures will also remain
warmer than normal, as the Saharan dust layer limits radiational
cooling. Heat indices will likely continue to reach hazardous levels
Tuesday afternoon. Residents and visitors are encouraged to continue
practicing heat safety measures to reduce the risk of heat-related
illnesses as additional heat products may be needed to be issued.

&&

.Long Term(Thursday through next Sunday)...
Issued at 156 PM AST Mon Jul 13 2026

During the long-term period the best chance to see some rainfall
will occur on Thursday as a weak upper-level low interacts with a
patch of low-level moisture moving across the islands. The latest
model guidance suggest precipitable water and mid-level relative
humidity increasing to the 50th and 75th percentile of for this time
of the year, providing sufficient moisture to support scattered
showers and the chance of a few isolated thunderstorms. While
widespread rainfall is not anticipated, moderate showers may produce
localized ponding in low-lying and poor drainage areas. Residents
with outdoor activities planned for Thursday should remain alert for
occasional interruptions from passing showers particularly during
the afternoon hour across the western half of Puerto Rico.

At the same time, moderate concentrations of Saharan dust are
expected to persist across the region on Thursday, resulting in hazy
skies and potentially limiting the coverage of shower activity.
People with respiratory illnesses or sensitivities should take the
necessary precautions, particularly during prolonged periods
outdoors. Saharan dust concentrations are forecast to gradually
decrease from late Thursday into the weekend, allowing for improving
visibility and air quality.

From Friday through Sunday, an upper-level ridge will strengthen
across the region while a drier air mass establishes over the
islands. This pattern will promote predominantly stable weather
conditions, with only brief, isolated showers expected.
Consequently, the weekend is expected to be favorable for most
outdoor activities.

Despite the drier conditions, forecast 925 mb temperatures remain
above the average for this time of year, supporting warm to hot
daytime conditions through the weekend. Residents and visitors are
encouraged to stay well hydrated, seek shade where possible, and
limit strenuous outdoor activities during the hottest part of the
day.

&&

.AVIATION...
(18Z TAFS)
Issued at 156 PM AST Mon Jul 13 2026

VFR conds will prevail across all terminals through the fcst
period. Limited VCSH/SHRA are more probable across the vicinity of
TJBQ thru 13/21Z. Main aviation concerns are the haze and winds. HZ
will increase further this evening and Tuesday over the local
islands, causing vis reductions. Gusty conds will prevail, with E-
ESE sfc winds at around 15 kt with gusts up to 30 kt will continue
through around 13/23Z, becoming lighter overnight. By 14/14Z, winds
are expected to pick up again.

&&

.MARINE...
Issued at 156 PM AST Mon Jul 13 2026

A strengthening high pressure system over the central Atlantic
will maintain moderate to locally fresh easterly winds, resulting
in choppy seas across the regional waters through mid-week. A
drier airmass along with moderate to high concentrations of
Saharan dust particles will continue to filter into the region
through Wednesday, promoting hazy skies and reduced visibilities.

&&

.BEACH FORECAST...
Issued at 156 PM AST Mon Jul 13 2026

Breezy trade winds will continue to generate choppy seas across the
local waters, resulting in a moderate risk of life-threatening
rip currents across many beaches of Puerto Rico and the U.S.
Virgin Islands through the next several days. The moderate risk
will remain along the northern and eastern beaches of Puerto Rico.
Beachgoers should swim near lifeguards whenever possible, heed
beach warning flags, and never swim alone.

Warm to hot conditions will continue this week along most local
beaches. Stay well hydrated, seek shade whenever possible, and
apply sunscreen to help reduce the risk of heat-related
illnesses.

&&

.FIRE WEATHER...
Issued at 156 PM AST Mon Jul 13 2026

Surface stations across southern Puerto Rico have been registering
relative humidity (RH) values and wind gusts near critical levels.
Therefore, a Fire Danger Statement remains in effect until 5 PM AST,
highlighting an elevated fire danger risk. A drier air mass will
dominate over the region from this evening through Wednesday along
with Saharan dust particles. Ongoing dry conditions and critically
dry fuels resulting from persistent rainfall deficits will continue
to favor rapid fire growth and spread across much of Puerto Rico,
Vieques, Culebra, and St. Croix. Additional fire weather products
are likely over the next few days, stay tuned to the forecast.

&&

.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.
&&

$$

SHORT TERM...YZR
LONG TERM....MMC
MARINE/BEACH FORECAST...GRS

NWS SJU Office Area Forecast Discussion