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564
FXCA62 TJSJ 051710
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
110 PM AST Tue May 5 2026

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

.KEY MESSAGES...
Updated at 110 PM AST Tue May 5 2026

* Near-normal moisture content combined with an upper-level
  trough will increase the chance of isolated to scattered showers
  this afternoon, particularly across the northwest quadrant of
  Puerto Rico.

* Mostly fair weather will prevail for the rest of the period,
  with passing trade wind moisture bringing isolated showers,
  mainly during overnight and morning hours.

* Warmer-than-normal temperatures will persist across Puerto Rico
  and the U.S. Virgin Islands, with heat indices reaching or
  exceeding 100 degrees F across urban and coastal areas.

* Moderate rip current risk will continue along northern and
  eastern exposed beaches through Thursday, improve to low risk on
  Friday, and then return to moderate by the weekend as winds
  increase.

&&

.Short Term(This evening through Thursday)...
Issued at 110 PM AST Tue May 5 2026

Partly cloudy skies prevailed across the U.S. Virgin Islands and
eastern Puerto Rico, including Vieques and Culebra, during the
morning hours, accompanied by a few passing light showers.
Meanwhile, clearer skies dominated western Puerto Rico early in the
day before gradually transitioning to partly cloudy conditions as
the morning progressed.

For the rest of the afternoon and overnight hours we anticipate the
development of showers and isolated lightning due to the proximity
of a trough, in combination with the available moisture, diurnal
heating, and local effects. This activity will mainly affect
windward areas of eastern Puerto Rico and the U.S. Virgin Islands,
with probabilities generally remaining in the limited to low range.
On Wednesday afternoon, localized convective activity is expected to
develop once again, particularly across the northwestern quadrant of
Puerto Rico. However, moisture availability will remain the primary
limiting factor despite some lingering dynamical instability aloft,
resulting in moderate probabilities of precipitation. These outcomes
will depend on the timing and extent of drier air intrusions, which
may re-establish inversion caps and suppress convection.

By Thursday, a more stable pattern is expected to take hold as drier
air filters into the region, further limiting convective
development. This will likely result in the least active day of the
period, with low probabilities of precipitation. Only isolated,
brief showers are expected across windward areas overnight, with
minimal afternoon activity across the interior and western sections
of Puerto Rico.

&&

.Long Term(Friday through Tuesday)...
Issued at 450 AM AST Tue May 5 2026

East to east-northeast flow to start the period will steer patches
of both drier and more humid air towards the region. Precipitable
Water (PWAT) values will generally be at below normal to low end
normal values for this time of the year. Available moisture will
also be shallow, mainly below 800 mb. With this below normal to
normal moisture and increasing subsidence (an upper level trough
will be moving away from the region to start the period and mid-
level ridging will build) a general reduction in shower activity and
rainfall coverage is forecast. A limited heat risk is also forecast
for most of the period, affecting sensitive individuals and
individuals with prolonged exposure and/or inadequate hydration.
Current model guidance suggests a more easterly steering flow to
start the next week, veering to become more easterly to east-
southeasterly to start the next workweek and continuing to bring
patches of both drier and more humid air. Up to breezy conditions
will be present, particularly to start the weekend onwards.

This will result in a limited non-thundersstorm wind risk, with
gusts up to around 25 mph at times at coastal and windward areas.
Unsecured items could blow around. Shower activity can continue to
reach windward sectors of the islands during the morning and
overnight hours while diurnal heating and local effects can
promote afternoon convection over mainly interior to western PR
with steering flow each day determining a more NW or SW movement.
Low concentrations of Saharan Dust will reach the area while the
bulk of a Saharan Air Layer will stay south of the local islands.
Under breezy conditions, increasing temperatures and with patches
of drier air approaching, the potential for elevated fire danger
remains, stay tuned for any future updates.

&&

.AVIATION...
(18Z TAFS)
Issued at 110 PM AST Tue May 5 2026

Mostly VFR condt are expected to prevail across all terminals.
However, brief MVFR possible with VCTS possible over TJBQ. VCSH
possible over TJSJ, TIST, TISX after 05/18Z. Winds will remain
around 12kts with occasional higher gusts, becoming light and
variable overnight.

&&

.MARINE...
Issued at 110 PM AST Tue May 5 2026

Surface high pressures and a frontal boundary over the Atlantic
will promote gentle to moderate easterly to southeasterly winds
through at least early Thursday, then becoming more easterly to
northeasterly. By the weekend, winds are expected to increase to
moderate to fresh levels across the regional waters. Seas will
range between 2 and 4 feet, occasionally higher due to a
combination of local wind waves and a few pulses of a small, long-
period northeasterly swell spreading across the Atlantic waters.
Overall, conditions will be favorable for small craft, though
operators should exercise caution at times due to wind-driven
seas and passing showers that may produce locally higher winds and
seas.

&&

.BEACH FORECAST...
Issued at 110 PM AST Tue May 5 2026

A moderate risk of rip currents will persist along the northern
and eastern beaches of Puerto Rico, as well as in northern areas
of Culebra, through Thursday. Across the U.S. Virgin Islands, the
risk will be moderate at St. Croix through tonight, then decrease
to low through the end of the week for St. Thomas and St. John.

By Friday, conditions are expected to gradually improve in Puerto
Rico as well, with a low risk prevailing across most beaches.
Remember that even when the risk is low, life-threatening rip
currents can still occur near groins, jetties, reefs, and piers.
By the weekend, breezier winds will bring back a moderate risk
across most beaches of the islands. For additional information and
location-specific rip current details, visit
weather.gov/beach/sju.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

SHORT TERM/AVIATION...MMC
LONG TERM...MRR
MARINE/BEACH...YZR

NWS SJU Office Area Forecast Discussion