845
FXCA62 TJSJ 161834
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
234 PM AST Sun Aug 16 2026

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

.KEY MESSAGES...
Issued at 231 PM AST Sun Aug 16 2026

 - A heat threat will persist through most of the workweek due to warm
   temperatures and heat indices ranging between 108 and 111
   degrees.

 - A drier weather pattern is expected from Monday through Wednesday
   as a generally drier air mass dominates the region. No
   significant rainfall accumulations are anticipated during the
   first part of the week. However, by Wednesday, an increase in
   moisture is forecast, leading to a greater potential for
   showers and a limited flooding risk, particularly across
   western portions of Puerto Rico.

 - By Thursday into Friday, a wetter and more unstable pattern is
   expected as a tropical wave moves across the region. Current
   guidance suggests an increase in shower and thunderstorm
   activity during this period.

 - A Low to Moderate Risk of Rip Currents is expected across the
   local beaches throughout the workweek.

&&

.Short Term(This evening through Tuesday)...
Issued at 231 PM AST Sun Aug 16 2026

Fair weather conditions with partly cloudy skies prevailed this
morning as the tropical wave moved away from the region.
Temperatures are ranging from the upper 80s to low 90s F across
urban and coastal areas, while temperatures are in the 70s to low
80s F in the mountainous regions. Conditions are breezy with gusty
periods, with maximum winds of 15 to 20 mph and gusts ranging from
20 to 29 mph, particularly near coastal stations. Moderate
concentrations of Saharan dust are also present across the region.

In the wake of the tropical wave, drier air has been filtering into
the region. The latest GOES-19 precipitable water imagery is showing
values around 1.4 to 1.6 inches, which are seasonal to below normal.
Combined with stable and dry conditions aloft, shower activity will
remain limited for the rest of today and Monday. However, daytime
heating and local effects could still trigger localized afternoon
showers across western Puerto Rico, but no flood risk is
anticipated. Easterly winds will gradually subside tonight and
throughout the rest of the short-term period as the pressure
gradient loosens across the Caribbean, with easterly to
northeasterly winds becoming more seasonal, around 10 to 15 knots.

By Tuesday afternoon, precipitable water (PWAT) values will
gradually increase toward more seasonal levels, which could result
in better coverage of afternoon showers across western Puerto Rico.
In addition, lighter winds could lead to slower-moving showers and
allow for some accumulation, particularly during the afternoon.
Therefore, a limited flood risk is anticipated across western Puerto
Rico on Tuesday afternoon.

A Heat Advisory remains in effect until 5 PM AST this afternoon. The
outlook for the short-term period in terms of heat is that an
elevated heat risk will persist, as reflected by above-normal 925-mb
temperatures, plenty of sunshine, and overall limited rainfall and
cloud cover. The recommendation is to remain hydrated and wear light-
colored clothing to limit the effects of heat-related illnesses.


&&

.Long Term(Wednesday through next Saturday)...
Issued at 231 PM AST Sun Aug 16 2026

Variable conditions are still expected in the long-term, with high
uncertainty during the second part of the workweek. A surface high
pressure building over the Western Atlantic should maintain winds
mainly from the E-ENE (shifting briefly from the E-SE on Thursday)
throughout most of the period, leading to breezy to locally windy
conditions. The latest global solutions indicate a tropical wave
(former AL94) approaching the Caribbean Basin and moving across the
CWA late Wednesday night into Thursday. According to the
deterministic guidance of the ECMWF and GFS, PWAT values may
increase to 2.0 - 2.2 inches, with a low chance of reaching 2.2 -
2.4 inches. Additionally, members of the grand ensemble are trending
toward wetter values during Thursday, with moisture content in the
low and mid levels reaching above climatological normal (around
80%). Under that pattern, lines of strong showers and thunderstorms
could move over windward sections of the islands throughout all day,
with afternoon convection over interior and western/northwestern
Puerto Rico. Rainfall accumulations could lead to ponding of water
over roadways and poorly drained areas, along with minor flooding.
Nevertheless, theres high uncertainty as the tropical wave
encounters unfavorable conditions such as drier airmass, Saharan
Dust, and strong wind shear. Although the NHC has ended , residents
and visitors should continue to monitor this system. As the tropical
wave moves out of the local area, a dry slot, along with
concentrations of Saharan Dust, should filter into the region, with
PWAT values dropping to below normal (1.2 - 1.4 inches).  Although
daytime heating and local effects may enhance afternoon convection,
showers and isolated thunderstorms could move over western Puerto
Rico, though rainfall accumulations will remain limited. By
Saturday, a perturbation in the trades, along with an upper-level
low, may increase moisture content across the CWA, with PWAT values
reaching typical values for this time of the year (between 1.6 and
1.8 inches). This may introduce some instability and enhance
convection across the area once again, as the frequency of showers
and thunderstorms may increase over windward sections.

&&

.AVIATION...
(18Z TAFS)
Issued at 231 PM AST Sun Aug 16 2026

Mainly VFR conds across TAF sites. Moderate concentrations of
Saharan dust are resulting in slight VIS reductions at least thru
this evening, then low concentrations the rest of the forecast
period. Breezy conditions with occasional gusts up to 28kts, winds
slightly reducing overnight, and picking up to 15 kts with gust 25
kts aft 17/14Z. VCSH possible overnight across USVI sites and TJSJ,
but overall no significant impacts.

&&

.MARINE...
Issued at 231 PM AST Sun Aug 16 2026

Hazardous marine conditions will persist through the rest of the
afternoon and into the evening hours due to breezy conditions
associated with a tight pressure gradient generated by a surface
high over the central Atlantic. By Monday morning, easterly winds
will become more moderate, allowing seas to gradually subside to 3
to 5 feet, with occasionally higher seas across localized areas.
Limited shower activity is expected from Monday through Wednesday.
However, by late Wednesday into Thursday, localized hazardous
marine conditions may develop with the arrival of a tropical wave
previously known as Invest 94L. Mariners are urged to exercise
caution, particularly across the offshore waters due to strong
thunderstorms and gusty winds.

&&

.BEACH FORECAST...
Issued at 231 PM AST Sun Aug 16 2026

Hazardous coastal conditions will persist through the rest of the
day and into the evening hours due to breezy conditions.
Therefore, a High Risk of Rip Currents remains in effect for
beaches along the northern, eastern, and southern coasts of Puerto
Rico, including Vieques and Culebra, as well as the U.S. Virgin
Islands. Improving conditions are forecast by Monday morning, with
a Moderate Risk of Rip Currents expected to prevail through much
of the workweek, potentially decreasing to a Low Risk by
Wednesday. Limited shower activity is expected from Monday through
Wednesday. However, by late Wednesday into Thursday, localized
hazardous coastal conditions may develop with the arrival of a
tropical wave previously known as Invest 94L. Beachgoers are urged
to exercise caution along the shoreline due to strong
thunderstorms and gusty winds.

&&

.FIRE WEATHER...
Issued at 231 PM AST Sun Aug 16 2026

Critical fuel conditions continue to persist across the islands,
with extreme drought conditions across portions of the southern
coastal plains and eastern Puerto Rico. In the wake of the tropical
wave, a drier airmass is present, resulting in relative humidity
values near or below critical levels. These conditions, combined
with little to no rainfall, ongoing rainfall deficits, stressed
vegetation, and dry fuels, will maintain conditions favorable for
rapid fire spread. The greatest concern remains across southern and
southwestern Puerto Rico, where fuels are particularly dry and
recent fire activity has been more frequent. A Fire Danger Statement
remains in effect until 5 PM AST this afternoon. Residents and
visitors are encouraged to avoid outdoor burning. Continue to
monitor the forecast, as additional fire weather products may be
needed in the coming days.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through late tonight for PRZ001>003-005-
     007-008-011>013.

     Heat Advisory until 5 PM AST this afternoon for PRZ001>005-007-
     008-010>013.

VI...High Rip Current Risk through late tonight for VIZ001-002.

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

AM...Small Craft Advisory until midnight AST tonight for AMZ711-733-
     735-741.

&&

$$

SHORT TERM,AVIATION & FIRE WEATHER...YZR
LONG TERM....MNG
MARINE, BEACH FORECAST & KEY MESSAGES...LIS