Flash Flood Warning 27, NWS JSJ

157 
WGCA72 TJSJ 092151
FFSSJU

Flash Flood Statement
National Weather Service San Juan PR
551 PM AST Sun Aug 9 2026

PRC097-092201-
/O.EXP.TJSJ.FF.W.0027.000000T0000Z-260809T2200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Mayaguez PR-
551 PM AST Sun Aug 9 2026

...FLASH FLOOD WARNING WILL EXPIRE AT 6 PM AST THIS EVENING FOR
MAYAGUEZ...

The heavy rain has ended. Flood waters are receding. Please continue
to heed remaining road closures.

&&

LAT...LON 1825 6711 1825 6706 1822 6705 1821 6703
      1820 6702 1819 6702 1817 6705 1817 6708
      1816 6708 1816 6713 1815 6714 1816 6717
      1817 6718 1817 6717 1821 6715 1822 6717
      1825 6717 1827 6719 1826 6714 1824 6713

$$

Area Forecast Discussion
National Weather Service San Juan PR
235 PM AST Sun Aug 9 2026

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

.KEY MESSAGES...
Issued at 214 PM AST Sun Aug 9 2026

- A Heat Advisory remains in effect through 5 PM for the lower
  elevations of Puerto Rico and the U.S. Virgin Islands.

- A drier air mass and suspended Saharan dust will build across
  the local region through Monday, suppressing widespread
  convective activity and leading to hazy skies and elevated heat
  indices through early Tuesday.

- Moisture returns rapidly late Tuesday ahead of an approaching
  tropical wave, increasing shower and thunderstorm coverage and
  restoring localized flooding risk.

&&

.Short Term(This evening through Tuesday)...
Issued at 214 PM AST Sun Aug 9 2026

A weak tropical wave and a dense Saharan Air Layer generated a
combination of showery and hazy conditions across the islands
early today. The Doppler radar estimated up to 2 inches of rain in
Rio Grande and less than half an inch across the eastern interior.
After the quick surge in morning showers, drier and hot conditions
prevailed in general through early this afternoon, with heat
indices ranging between 104F-112F across most coastal and urban
areas of the lower elevations of PR and the USVI. For the rest of
this afternoon, breezy and hazy conditions will prevail, with
locally induced showers developing mainly over the west coast of
PR.

Similar conditions will continue on Monday as a patch of dry,
Saharan dust-laden air lingers over the northeastern Caribbean.
Layered precipitable water observations and regional aerosol
guidance indicate precipitable water dropping sharply toward the
25th percentile (near 1.50 inches), while mid-level relative
humidity falls below 30 percent. Strong mid-level subsidence will
cap deep convection across most of PR and the USVI through Monday
night into early Tuesday. Under hazy skies, daytime heating and
surface humidity will push heat indices once again around 108F
along coastal and urban areas, warranting another heat advisory
issuance.

By Tuesday, the dust mass shifts westward as the leading edge of a
tropical wave arrives from the east. Deep-layer moisture will
rapidly increase, pushing precipitable water back above 1.80
inches. High-resolution guidance and atmospheric soundings
indicate rising 850–700 mb relative humidity alongside falling 500
mb temperatures, destabilizing the atmosphere. As a result,
coverage of scattered showers and thunderstorms is expected to
increase in general across the islands, shifting the primary
hazard back toward urban flooding and localized river rises
heading into mid-week.

&&

.Long Term(Wednesday through next Saturday)...
Issued at 214 PM AST Sun Aug 9 2026

Weather conditions during the long-term period will start off
variable as a tropical wave moves over the islands and wind speeds
continue to gradually increase. Precipitable water (PWAT) values
will start off at generally normal values (up to around 2 inches) as
the wave moves over the islands. The interaction between this wave
and the atlantic surface high will result in a breezy to locally
windy, E to ESE, steering flow. Along with diurnal heating, sea
breeze convergence and local effects, this setup will help trigger
afternoon convection across interior to W-NW PR, as well as lines of
showers downwind of El Yunque and the local islands. Passing showers
will also reach windward sectors. The heaviest showers could promote
ponding of water and sustain a flooding risk. Low to moderate
concentrations of Saharan Dust will also persist to start the long
term period and continue through at least the workweek. Drier air
will reach the islands on Thursday, limiting widespread shower
activity, with breezy to locally windy flow also limiting
accumulations. Increasing uncertainty develops Friday onward as the
tropical waves that would affect the region Friday and during the
next weekend are currently being monitored by the National Hurricane
Center (NHC). The latest 2 AM Tropical Weather Outlook has these
waves with a low and medium formation chance, respectively.
Although the forecast has been based on the typical weather
pattern under generally increasing moisture and breezy to windy
easterly flow. Due to the extended forecast window, adjustments to
the track and intensity of the moisture remain possible toward
the end of the period. Please continue to monitor the latest
Tropical Weather Outlooks (TWOs) issued by the NHC for more
information regarding the formation chance of these tropical
waves.

&&

.AVIATION...
(18Z TAFS)
Issued at 214 PM AST Sun Aug 9 2026

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hours. VCTS possible at TJBQ thru 09/23z. The
09/12z TJSJ sounding indicated ENE winds at 28 kt just blo FL020.
HZ due to Saharan dust will continue through Monday, and VSBY may
drop to 6SM.

&&

.MARINE...
Issued at 214 PM AST Sun Aug 9 2026

A combination of a surface high pressure over the central Atlantic
and a passing tropical wave continue to promote breezy conditions
across the local waters, resulting in occasionally choppy seas of up
to 6 feet. Therefore, small craft operators should exercise caution
across the regional waters. Showers and thunderstorms associated
with the tropical wave are expected to remain across the local
waters, resulting in locally hazardous marine conditions. Another
tropical wave will approach the region by Tuesday, increasing the
potential for showers and thunderstorms over the local waters. By
the end of the workweek, a strengthening surface high over the
central Atlantic will promote increasing easterly winds, resulting
in hazardous conditions for small craft, with winds of 15 to 20
knots, locally up to 25 knots, and seas potentially building to 5 to
7 feet.

&&

.BEACH FORECAST...
Issued at 214 PM AST Sun Aug 9 2026

A moderate risk of rip currents will continue along the northern,
eastern, and southeastern beaches of Puerto Rico, Culebra, Vieques
and St. Croix through at least Tuesday. Breezy easterly winds
associated with a surface high pressure over the central Atlantic
and passing tropical waves will maintain choppy surf conditions,
particularly along exposed northern and eastern beaches. A low risk
will return on Wednesday across most beaches, before increasing to
moderate Thursday and potentially high Friday into next weekend as
easterly winds strengthen significantly in response to the high
pressure system.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory until 5 PM AST this afternoon for PRZ001>005-007-
     008-010>013.

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

AM...None.

&&

AVIATION/SHORT TERM...DSR
LONG TERM...MRR
BEACH/MARINE...GRS

Special Weather Statement
National Weather Service San Juan PR
337 PM AST Sun Aug 9 2026

PRZ007-009>011-092030-
Mayaguez and Vicinity PR-Western Interior PR-Southwest PR-
Ponce and Vicinity PR-
337 PM AST Sun Aug 9 2026

...A STRONG THUNDERSTORM WILL IMPACT WESTERN INTERIOIR
MUNICIPALITIES THROUGH 430 PM AST...

At 336 PM AST, Doppler radar was tracking a strong thunderstorm near
Mayaguez, moving west at 25 mph.

HAZARD...Wind gusts up to 35 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Rincon, Hormigueros, Las Marias, Mayaguez, Anasco, La Playa, Maricao,
Stella, and Espino.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 1823 6690 1810 6691 1810 6719 1813 6717
      1814 6718 1816 6718 1821 6715 1822 6717
      1829 6719 1830 6724 1836 6727
TIME...MOT...LOC 1936Z 104DEG 24KT 1819 6708

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...40 MPH

LIS