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674
FXCA62 TJSJ 120745
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
345 AM AST Thu Nov 12 2026

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

.KEY MESSAGES...
Issued at 345 AM AST Thu Nov 12 2026

- The main hazard over the coming days will be the heat. Hot,
  humid conditions will pose the highest risks across coastal
  areas, lowlands, interior valleys, and urban zones. A Heat
  Advisory is in effect today from 10 AM to 5 PM AST.

- Generally fair weather will prevail over the coming days,
  however, a few showers are expected across the USVI and PR`s
  windward areas in the mornings, with localized afternoon shower
  development across southeast and northwest PR.

- Southeast winds will gradually increase, becoming breezy,
  especially Friday and Saturday.

- Life-threatening rip currents will remain possible (moderate
  risk) across most local beaches of PR and USVI throughout the
  forecast period.

&&

.Short Term(Today through Saturday)...
Issued at 345 AM AST Thu Nov 12 2026

Satellite and radar imagery showed mainly clear skies and fair
weather conditions during the overnight period. Surface
observations registered temperatures in the mid to upper 70s
across coastal areas and in the 60s to low 70s across mountainous
regions. Winds remained light and variable.

A mid to upper-level ridge near the region will maintain
subsidence and dry air aloft, favoring generally fair weather
across most of Puerto Rico and the U.S. Virgin Islands throughout
the forecast period. At the surface, seasonal precipitable water
values will prevail. The main weather hazard today, and likely
over the coming days, will be the heat due to the combination of
southeast winds and low-level moisture. A Heat Advisory is in
effect from 10 AM to 5 PM AST for Puerto Rico and the U.S. Virgin
Islands. Hot and humid conditions will pose the greatest risks
across coastal areas, lowlands, interior valleys, and urban areas.

Today, a shortwave trough passing north of the islands will
slightly weaken the ridge pattern aloft, allowing for a slight
increase in moisture levels between 850 and 500 mb. Consequently,
the frequency of passing showers will increase across eastern to
southern portions of Puerto Rico and the U.S. Virgin Islands,
particularly during the afternoon and evening. Daytime heating and
local effects may trigger isolated to scattered showers across
portions of northwestern Puerto Rico. However, overall atmospheric
stability will dominate and should keep rainfall activity
localized.

On Friday and Saturday, a surface high pressure over the central
Atlantic, along with the mid to upper-level ridge prevailing
across our area, will result in persistent subsidence and limited
shower coverage. The main weather concerns will remain the heat
and southeast winds, which are expected to become breezier on
those days as the pressure gradient tightens across the eastern
Caribbean.

&&

.Long Term(Sunday through Thursday)...
Issued at 345 AM AST Thu Nov 12 2026

No major changes were introduced to the long-term forecast. The
interaction with a surface high pressure over the Central Atlantic
and a frontal boundary north of the CWA should slightly weaken
local pressure gradient, maintaining a E-SE wind flow. Aloft, a
mid-level ridge in the vicinity should dominate most of the
weather pattern, as model guidance suggest slightly warmer than
normal mid-level temperatures throughout most of the forecast
period. Sunday should be the less active day of the long-term, as
model guidance suggest well below normal moisture content in the
low and mid levels. Shower activity (if any) during the afternoon
should remain isolated and short-lived. On Monday, model guidance
suggest the arrival of a patch of moisture in the early morning,
increasing frequency of showers over windward areas. From the
latest model solutions, it seems that PWATs may push back into
normal values, however, it mainly concentrates in the 1000-850 and
300 - 200 mb layers, while the mid-levels remain dry.
Additionally, the latest NASA AOT suggest low concentrations of
SAL lingering in the CWA. Although these conditions will limit
deep convection, daytime heating and local effects will trigger
afternoon convection across interior and western/northwestern
Puerto Rico. Rainfall accumulations could increase the likelihood
of ponding of water over roadways and poorly drained areas, though
the urban and small stream flood should remain isolated. A
similar weather pattern can be expected on Tuesday and Wednesday,
though the flood threat should remain low.

&&

.AVIATION...
(06Z TAFS)
Issued at 345 AM AST Thu Nov 12 2026

Mainly VFR conditions are expected to prevail across all TAF sites
during the forecast period. However, locally induced VCSH/-SHRA
may develop in and around TJBQ/TISX/TIST/TJPS between 12/17-22Z.
This can result in intermittent/brief MVFR conds. SE winds up to
12 kt with sea breeze variations and gusts up to 18 to 20 kt (in
TJSJ and TJPS) expected aft 12/13-14z.

&&

.MARINE...
Issued at 345 AM AST Thu Nov 12 2026

Surface high pressure over the central Atlantic will strengthen
east- to-southeast trade winds through Saturday, with winds
increasing to 15 to 20 knots and gusts up to 30 knots,
particularly Friday. Although the northerly swell will continue to
subside, increasing wind-driven seas will produce choppy to
locally rough conditions, with seas generally between 3 and 6
feet, occasionally reaching 8 feet across portions of the offshore
waters and local passages. Small craft should exercise caution,
with the most hazardous conditions expected Friday. Showers and
isolated thunderstorms may produce locally higher winds and seas.
Marine conditions should gradually improve Sunday into early next
week.

&&

.BEACH FORECAST...
Issued at 345 AM AST Thu Nov 12 2026

A moderate risk of life-threatening rip currents will persist
through Saturday along most northern and eastern beaches of Puerto
Rico, Culebra, Vieques, and the U.S. Virgin Islands, extending
into portions of the southern and western beaches. Beginning
Sunday, some improvement is expected as the risk gradually
decreases to low along more of the southern and western beaches of
Puerto Rico and portions of the smaller islands. However, a
moderate risk will continue along exposed northern and eastern
beaches through early next week. Beachgoers should remain
cautious, as life-threatening rip currents are possible in the
surf zone. Lightning may pose an additional hazard where afternoon
thunderstorms develop.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
     for PRZ001>013.

VI...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
     for VIZ001-002.

AM...None.
&&

$$

SHORT TERM/AVIATION...YZR
LONG TERM...MNG
MARINE/BEACH...ICP

NWS SJU Office Area Forecast Discussion