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043
FXCA62 TJSJ 201703
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
103 PM AST Wed May 20 2026

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

.KEY MESSAGES...
Issued at 1215 PM AST Wed May 20 2026

* Breezy conditions across the local islands will continue to
  bring fast moving showers, resulting in a limited to elevated
  flooding risk. Additionally, gusty winds may blow around
  unsecured items.

* Under the prevailing east-southeasterly flow, heat indices will
  remain between 100 and 105F. This will primarily affect heat-
  sensitive individuals, especially those outdoors without
  adequate cooling or hydration.

* The breezy conditions will continue to promote moderate rip
  current risk across most coastal areas.

* Regarding the marine conditions expect choppy to rough seas at
  times. Small Craft Advisories remain in effect through at least
  Thursday afternoon for the offshore Atlantic waters.

* Across the U.S. Virgin Islands, the main hazards continue to be
  heat indices around 100F and a moderate risk of rip currents,
  particularly for Saint Croix.

&&

.Short Term(This evening through Friday)...
Issued at 1215 PM AST Wed May 20 2026

Variably cloudy skies prevailed across the islands today, with frequent
showers observed over the surrounding waters and eastern coastal
areas of Puerto Rico. Localized afternoon convection in western
Puerto Rico will remain possible until sunset. East-southeasterly
winds of 15 to 20 mph continued throughout the day, while coastal
temperatures ranged from the upper 80s to low 90s.

Latest guidance suggests that 250 mb heights will gradually rise as a
mid- to upper-level trough over the western tropical Atlantic
weakens and shifts further west. At lower levels, surface high
pressure anchored over the north-central Atlantic will promote
fresh to locally strong east-southeasterly winds. In fact, 925 mb
winds are expected to persist near 20 knots, which is near or
above the climatological normal for this time of year. Moisture
will remain mostly confined below 700 mb, with precipitable water
values staying near seasonal normals through Friday, followed by a
sharp increase in available moisture.

Maximum temperatures are expected to range from the low to mid-80s in
higher elevations to the upper 80s and low 90s along coastal
areas. Temperatures at the 925 mb level are forecast to peak on
Thursday and Friday, making them the warmest days of the forecast
cycle. Limited dust concentrations will also continue.

Under this evolving pattern, passing showers will continue over
eastern Puerto Rico and the outlying islands, with locally induced
afternoon convection developing over western Puerto Rico Thursday
and Friday. Breezy conditions will drive fast-moving showers and a
limited risk of localized flooding, while gusty winds may affect
unsecured items. Finally, heat indices between 100 and 105F will
primarily impact heat-sensitive individuals and those outdoors
without proper hydration.

&&

.Long Term(Saturday through next Tuesday)...
Issued at 1215 PM AST Wed May 20 2026

No major changes were introduced to the long-term forecast. As
mentioned in the previous discussion, a broad surface high pressure
will linger over the Western Atlantic through most of the period,
promoting E-ESE winds and resulting in breezy to locally windy
conditions across the CWA. Instability should gradually increase
Saturday onwards, as an upper-level trough extending into the
tropics may shift eastward and linger north of the CWA. According to
the latest model guidance, moisture content will increase as well,
with PWAT values approaching near-normal levels (up to 2.0 inches).
Additionally, the latest Grand Ensemble shows members tending to
wetter conditions for the first part of next workweek (difference
around 0.2 - 0.3 inches), increasing confidence. Under the influence
of the trough, mid-level temperatures may become slightly cooler
than normal (near -9 degrees Celsius), while winds aloft may become
stronger and allow ventilation. Additionally, the latest Galvez-
Davison Index (GDI) solutions dont rule out the potential for
isolated to scattered thunderstorms across the islands each day,
becoming frequent Monday onward during afternoon into night hours.
Hence, windward sections of the islands can expect passing showers
moving each day, while afternoon showers and thunderstorms will
likely concentrate over western/northwestern Puerto Rico. Due to
strengthening winds, showers should remain progressive, with
rainfall accumulations likely to result in ponding of water over
roadways and poorly drained areas, including minor flooding.
Nevertheless, urban and small streams flooding cannot be ruled out
over the aforementioned areas.

As mentioned in the previous discussion, warmer than normal
temperatures and abundant moisture content will increase the
likelihood of heat indices exceeding 100 degrees Fahrenheit.
Although a limited risk is expected across low elevations and urban
areas of the islands, individuals sensitive to heat must take
necessary precautions, such as remaining hydrated and avoiding long
sun exposure.

&&

.AVIATION...
(18Z TAFS)
Issued at 1215 PM AST Wed May 20 2026

VFR conditions across all TAF sites. Winds will bring occasional
rounds of -SHRA/SHRA around windward terminals thru 20/23Z,
SHRA/+SHRA and VCTS, will develop across the interior and NW
resulting in brief MVFR conds over TJBQ. Each day, expect breezy
to locally windy E to ESE winds at 15-20 kts with higher gusts and
sea breeze var, decreasing after 23Z.

&&

.MARINE...
Issued at 1215 PM AST Wed May 20 2026

Marine conditions will remain somewhat hazardous through the next
several days as strong high pressure over the Atlantic continues to
support moderate to fresh easterly winds across the regional waters.
Winds will occasionally reach locally strong levels, resulting in
choppy to rough seas at times. Small Craft Advisories remain in
effect through at least Thursday afternoon for the offshore
Atlantic waters. In addition, isolated afternoon and early evening
thunderstorms may develop each day across the western coastal
waters of Puerto Rico, producing locally higher winds and seas
near storms.

&&

.BEACH FORECAST...
Issued at 1215 PM AST Wed May 20 2026

Moderate rip current risk conditions are expected to persist across
most local beaches through much of the week and into the upcoming
weekend due to persistent breezy conditions and ongoing wind-driven
seas. The highest risk will continue to be along north and east-
facing beaches. Beachgoers should exercise caution, avoid swimming
alone, and remain near lifeguard-protected beaches whenever
possible, as life-threatening rip currents can develop even under
moderate risk conditions.

&&

.FIRE WEATHER...
Issued at 1215 PM AST Wed May 20 2026

Increased moisture could prevent RH values from decreasing below
threshold values for prolonged periods; however, rainfall should
again remain limited across the southern plains, allowing relative
humidity to drop to critical fire weather thresholds in the
region. Additionally, sustained winds of 15 to around 20 mph, with
higher gusts, combined with elevated KBDI values, will favor the
rapid spread of wildfires across the southern coastal plains. The
low 7-day percent of normal rainfall will also persist across the
southeastern coastal plains. Fire management partners are once
again urged to remain vigilant.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...Small Craft Advisory until 6 PM AST Thursday for AMZ711.

&&

$$

SHORT TERM...OMS
LONG TERM...MNG
AVIATION/MARINE/BEACH FORECAST/FIRE WEATHER...MMC

NWS SJU Office Area Forecast Discussion