Flash Flood Warning 26, NWS JSJ

689 
WGCA72 TJSJ 232054
FFSSJU

Flash Flood Statement
National Weather Service San Juan PR
454 PM AST Sat May 23 2026

PRC097-232104-
/O.EXP.TJSJ.FF.W.0026.000000T0000Z-260523T2100Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Mayaguez PR-
454 PM AST Sat May 23 2026

...FLASH FLOOD WARNING WILL EXPIRE AT 5 PM AST THIS AFTERNOON FOR 
MAYAGUEZ COUNTY...

The heavy rain has ended. Please continue to heed remaining road 
closures.

&&

LAT...LON 1827 6719 1827 6718 1826 6718 1826 6716
      1824 6712 1825 6707 1825 6706 1823 6705
      1822 6704 1819 6702 1817 6708 1815 6709
      1816 6710 1816 6711 1816 6713 1816 6717
      1817 6718 1820 6715

$$

LIS

Area Forecast Discussion
National Weather Service San Juan PR
148 PM AST Sat May 23 2026

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

.KEY MESSAGES...
Issued at 148 PM AST Sat May 23 2026

* Morning showers across windward areas of Puerto Rico and the
  U.S. Virgin Islands will be followed by afternoon showers and
  isolated thunderstorms, particularly across central and western
  Puerto Rico.

* Across the U.S. Virgin Islands, isolated to scattered showers
  are expected mainly during the overnight and morning hours.

* Breezy to locally windy conditions will continue through the
  weekend, increasing further on Monday. Secure loose objects,
  especially along coastal areas.

* Moderate to fresh winds will result in choppy seas and a
  moderate risk of rip currents across most local beaches, likely
  increasing to a high risk by Monday. Small craft operators
  should exercise caution, and the issuance of a Small Craft
  Advisory cannot be ruled out early next week.

&&

.Short Term(This evening through Monday)...
Issued at 148 PM AST Sat May 23 2026

An active weather pattern is unfolding across the forecast area
due to a combination of strong deep-layer moisture and favorable
large- scale dynamics. The 23/12Z TJSJ upper-air sounding
indicated a moist, moderately unstable atmospheric profile with
Precipitable Water (PWAT) near 1.80 inches and a CAPE of 1164
J/kg. Both satellite imagery and CIMSS Total Precipitable Water
product highlights a broad plume of moisture across the eastern
Caribbean. At the upper levels, a WSW jet of 60 kts will support
divergence aloft. Model guidance forecasts a mid-level moistening
trend through the rest of the Holiday weekend. The 700-500 mb
relative humidity is expected to peak near 80%, while PWAT values
push upwards towards 2.00 inches, both variables are in the 75th
percentile of climatology for late May. Given this environment,
scattered to widespread showers and isolated thunderstorms are
expected.

For the rest of today, high-res ensemble guidance shows strong
consensus that daytime heating and orographic lifting with trades
around 15-20 knots will favor heavy rainfall over the interior and
western portions of Puerto Rico, with rainfall accumulations of 1.50
to 2.50 inches. This will pose a threat of ponding on roads and
localized urban flooding, as well as rapid rises along small
streams. Similar conditions are expected on Sunday, with somewhat
less moisture content available on Monday, as PWAT drops slightly to
near 1.75 inches. However, showers and isolated thunderstorms are
still expected to develop over the same areas as in previous days.

Meanwhile, the U.S. Virgin Islands will sit upstream of the primary
orographic forcing, keeping shower activity more scattered. While
brief heavy downpours cannot be ruled out within passing trade
showers, overall accumulations through Monday across the USVI are
expected to remain between 0.50 and 1.00 inches. Breezy conditions
are expected, particularly on Monday.

&&

.Long Term(Tuesday through Saturday)...
Issued at 326 AM AST Sat May 23 2026

Variable conditions are likely in the long term, with wet and
slightly unstable conditions near the next midweek, transitioning to
seasonal conditions by the upcoming weekend. As mentioned in
previous discussions, a surface high pressure is expected to extend
into the central Atlantic, promoting east-southeasterly winds,
remaining breezy across coastal areas. In the mid to upper levels,
there’s a lingering upper-level trough extending into the region
while a ridge tries to build over the western Atlantic. From the
latest deterministic guidance, PWAT values are still anticipated to
increase (most likely between 1.8 and 2.0 inches) from early Tuesday
to Wednesday as tropical moisture pools into the region and the
influence of the trough. Additionally, the latest ensemble member
agrees to above normal moisture content across the CWA, with 25th
and 75th percentiles close (mean around 1.9 inches). The influence
of the trough should maintain cool mid-level temperatures (500 mb
temperatures between -7 and -8 degrees Celsius), with divergence
aloft that should allow cloud growth. Additionally, the latest model
solutions keep suggesting areas of enhanced vorticity, near eastern
areas of the CWA, that should increase instability as well. Given
the expected conditions and considering local effects and diurnal
heating, the most likely scenario could be isolated to scattered
showers moving over the U.S. Virgin Islands and eastern portions of
Puerto Rico, including Vieques and Culebra, with afternoon
convection over interior and northwestern Puerto Rico. In addition,
island streamers could also develop and likely move over the waters
into portions of eastern Puerto Rico. Rainfall accumulations could
lead to urban and small stream flooding, with localized flash
flooding over the aforementioned areas. In addition to flooding,
some other hazards may include gusty winds and lightning. From
Wednesday onwards, uncertainty increases as concentrations of SAL
may approach and gradually filter into the region. Nevertheless,
considering that the latest model guidance is now suggesting warmer-
than-normal temperatures, daytime heating, and available moisture
may break and result in shallow convection over interior and
northwestern Puerto Rico. Although showers are expected, the
flooding threat should remain low.

As temperatures may increase and remain warmer than normal, with the
available moisture, the heat threat will likely remain limited,
affecting mostly individuals sensitive to heat, who must take
necessary precautions. Additionally, with concentrations of SAL that
may filter into the region, people sensitive to these particles
should exercise caution as well and stay up to further updates.

&&

.AVIATION...
(18Z TAFS)
Issued at 148 PM AST Sat May 23 2026

Tempo MVFR conds are possible thru 23/18z at TISX/TIST/TJSJ, and
once again btw 24/08-12z due to passing SHRA. At TJBQ/TJPS, MVFR
to brief IFR conds are possible thru 23/21z due to locally induced
SHRA/TSRA. SCT-BKN cigs btw FL030-050 and mtn tops obscd expected
across all the islands. The latest 23/12z TJSJ sounding indicated
ENE winds up to 24 kt blo FL040.

&&

.MARINE...
Issued at 148 PM AST Sat May 23 2026

Moderate to fresh easterly winds will persist across the regional
waters through the rest of the weekend and are expected to
strengthen from fresh to locally strong on Monday due to strong
high pressure over the central Atlantic. Choppy seas up to 6 feet
will continue across the offshore waters and local passages, where
small craft should exercise caution. Marine conditions are likely
to deteriorate from Monday into Tuesday as winds strengthen and
seas build up to 7 feet across portions of the offshore Atlantic
waters, likely prompting the issuance of Small Craft Advisories.
Isolated thunderstorms are expected to develop during the
afternoon and early evening across the western waters of Puerto
Rico.

&&

.BEACH FORECAST...
Issued at 148 PM AST Sat May 23 2026

A moderate risk of rip currents will persist through the rest of
the weekend for most beaches in Puerto Rico and the U.S. Virgin
Islands. Breezy to locally windy conditions will continue, with
winds and seas expected to increase further early next week. This
will likely lead to a high risk of rip currents across many
exposed beaches from Monday into Tuesday.

Afternoon thunderstorms are also possible each day across western
Puerto Rico. Residents and visitors should seek shelter
immediately if thunder is heard. 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...DS
LONG TERM...MNG
MARINE/BEACH...YZR