Flash Flood Warning 20, NWS JSJ

719 
WGCA72 TJSJ 302013
FFSSJU

Flash Flood Statement
National Weather Service San Juan PR
413 PM AST Wed Apr 30 2025

PRC043-302023-
/O.CAN.TJSJ.FF.W.0020.000000T0000Z-250430T2030Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Coamo PR-
413 PM AST Wed Apr 30 2025

...FLASH FLOOD WARNING FOR COAMO COUNTY HAS BEEN REPLACED WITH A 
FLOOD ADVISORY...

Light to moderate showers continue in the area, but the threat of 
flash flooding has decreased. If additional rainfall develops, 
another flash flood warning could be issued.

&&

LAT...LON 1816 6641 1817 6637 1817 6635 1817 6632
      1815 6631 1813 6632 1809 6626 1808 6626
      1807 6628 1805 6631 1803 6631 1802 6633
      1804 6636 1803 6637 1804 6643 1809 6643
      1810 6642 1812 6643 1814 6642 1818 6644

$$

ERG

Area Forecast Discussion
National Weather Service San Juan PR
501 AM AST Wed Apr 30 2025

.SYNOPSIS...

The wet and unstable weather pattern will continue through at least
Thursday evening due to a series of troughs and abundant moisture.
Soil saturation and soaring rivers will promote an elevated to
significant flooding threat, including minor flooding, flash
flooding, river flooding, and landslides in steep terrain. Although
an improvement of weather conditions is anticipated by this
weekend, abundant moisture will trigger showers and thunderstorms
in the afternoon.

&&

.SHORT TERM...Today through Friday...

Showers will continue to increase this morning across the U.S.
Virgin Islands and eastern Puerto Rico through the rest of the
morning hours. Ponding of water on roads and in poor drainage areas
is expected with this shower activity. Some showers could grow into
thunderstorms before noon across the mountain ranges of PR and last
through the evening hours. Due to already saturated soils and above
normal streamflows from previous days heavy rainfall, quick river
rises, mudslides, and flash flooding is likely with these
thunderstorms.

The wet weather pattern will continue through the rest of the short-
term period as abundant moisture content(PWAT above 2.00 inches)
lingers over the region. Later today, a cut off low is expected to
develop just northeast of the Leeward Islands from a mid-to upper
level trough over the central Atlantic. Global guidance suggest that
another but weak low reflected at the mid-levels will develop near
Cuba and Hispaniola on Thursday. These features will further enhance
instability across the northeastern Caribbean with colder than
normal 500 mb temperatures around -9C, and as they slowly drift
eastward a 75-80 kt jet segment will meander over the islands
through Friday. Therefore, thunderstorms over the next few days
could produce frequent lightning, small hail, and strong gusty winds
as well as further supporting long lasting rainfall activity over
the islands. Residents and visitors are urge to monitor the weather
conditions and remain vigilant to take necessary action to protect
life and property from the expected flooding impacts.

For more information please refer to the latest updates from the
Hydrologic Outlook(ESFSJU).

https://forecast.weather.gov/wwamap/wwatxtget.php?cwa=SJU&wwa
=hydrologic%20outlook

&&

.LONG TERM...Saturday through Wednesday...

The long-term forecast suffered some changes. Winds on Saturday
will remain from the northeast, and will shift from the southeast
due to a surface high pressure building in the Western Atlantic
and the induced low in the Central Atlantic moving southward. The
latest model ensemble members are shifting to a wetter scenario
this weekend, with PWAT values above climatological normal (1.8 -
2.0 inches). The 500 mb temperatures should remain colder (-7 to
-8 Celsius), and the latest model guidance keeps suggesting that
the upper dynamics will remain stronger with winds in the 250 mb
layer around 70 knots, providing ventilation aloft. Additionally,
the Galvez-Davison Index (GDI) also displays the potential of
isolated thunderstorms mainly in the afternoons. Although model
guidance keeps suggesting drier air filtering in the upper levels
due to ridging, above-normal low to mid-level moisture content in
the region will trigger shower and thunderstorm activity in the
afternoons along interior Puerto Rico, moving into northern/western
Puerto Rico in the early evenings. Due to the heavy rainfall,
saturated soils, and soaring rivers, the risk of flooding will
remain limited, with mostly ponding of water in roadways, urban,
and poorly drained areas, along urban and small stream flooding.

Another mid to upper-level trough should move north of the
Caribbean, and induce a surface low. The interaction of this low and
a surface high pressure in the Central Atlantic could promote
southerly winds throughout the period. With this pattern, winds
may pool well above-normal moisture content into the region by
late Tuesday, with PWAT values around 2.0 - 2.2 inches for the
rest of the forecast period. The best moisture content might stay
in the east side of the CWA, impacting eastern sections of Puerto
Rico, Vieques, Culebra, and the U.S. Virgin Islands. However,
deeper afternoon convection should develop over interior Puerto
Rico, elevating once again the flooding potential.

With the southerly component in the winds and abundant moisture,
is likely to observe near above-normal temperatures during this
period. However, the heat risk will remain low for the rest of the
forecast period.

&&

.AVIATION...

(06Z TAFs)

Mainly VFR early in the fcst period. However, SHRA increasing from
the Atlantic and eastern waters of the islands will move at times
across the USVI/Eastern PR terminals thru the morning hours. This
can lead to brief MVFR cigs. SHRA/TSRA will develop btw 30/15z-23z
over the mountains and drift mainly southward under 8-14 kt ENE
winds. Therefore, expect mtn tops obscd across PR and tempo MVFR to
IFR conds mainly at TJPS. Elsewhere, -RA/VCTS expected thru the
evening hours.

&&

.MARINE...

A surface high pressure building in the Western Atlantic and a
deep layered trough will promote light to moderate east- northeast
to northeast winds for the next few days. Showers and thunderstorms
are expected to develop across the local waters, producing locally
higher winds and seas. Small craft should exercise caution and stay
weather alert.

&&

.BEACH FORECAST...

No significant swell events is anticipated for the next few days.
However, the moderate risk of rip currents will continue for the
beaches in northern Puerto Rico, and possibly for Culebra and the
northern USVI by tomorrow into the weekend.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

SHORT TERM/AVIATION...DS
LONG TERM/MARINE...MNG

Hazardous Weather Outlook
National Weather Service San Juan PR
512 AM AST Wed Apr 30 2025

AMZ711>745-PRZ001>013-010915-
San Juan and Vicinity-Northeast-Southeast-Eastern Interior-
North Central-Central Interior-Ponce and Vicinity-Northwest-
Western Interior-Mayaguez and Vicinity-Southwest-Culebra-Vieques-
The nearshore and off shore Atlantic and Caribbean Coastal Waters-
512 AM AST Wed Apr 30 2025

This Hazardous Weather Outlook is for portions of Puerto Rico.

.DAY ONE...Today and Tonight

.Lightning...Isolated to scattered thunderstorms, particularly
across central Puerto Rico. Be prepared to stop all outdoor
activities and seek shelter if storms develop.

.Excessive Rainfall...Life-threatening flash flooding, which may
enter structures and cut off neighborhoods, especially in flood-
prone areas across mountainous areas. Elsewhere, prepare for
ponding of water on roads and in poorly drained areas, and
flooding in urban areas, roads, small streams, and washes. Stay
alert for rising water.

.Rip Currents...Life-threatening rip currents are possible in the
surf zone, particularly across the north-facing beaches. Isolated
stronger rip currents may occur elsewhere, especially near piers,
jetties, and channels.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

An unstable and wet weather pattern will result in shower and
thunderstorm development each afternoon through the end of the
week, increasing the risk of flash flooding and the potential for
frequent lightning and gusty winds with the expected thunderstorms,
particularly on Thursday. A moderate rip current risk will prevail
across the north facing beaches of the islands through the weekend.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is encouraged. Please relay any information
about flooding, winds, waves, and rip currents to the National
Weather Service in San Juan.

AMZ716-726-VIZ001-002-010915-
St. Thomas St. John adjacent Islands-St Croix-
Nearshore Atlantic and adjacent Caribbean Coastal Waters-
512 AM AST Wed Apr 30 2025

This Hazardous Weather Outlook is for portions of USVI.

.DAY ONE...Today and Tonight

.Lightning...Isolated thunderstorms expected at times. Stay alert
and be prepared to take shelter if storms develop.

.Excessive Rainfall...Ponding of water in roads and poorly drained
areas expected. There is a low chance of localized urban
flooding.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

Shower and thunderstorm development is expected to continue
through the end of the week, increasing the risk of urban
flooding and the potential for lightning activity and gusty winds,
particularly on Thursday. A moderate rip current risk is expected
on Thursday and Friday across the northern islands.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is encouraged. Please relay any information
about flooding, winds, waves, and rip currents to the National
Weather Service in San Juan.

Special Weather Statement
National Weather Service San Juan PR
113 PM AST Wed Apr 30 2025

PRZ006-007-301815-
Central Interior PR-Ponce and Vicinity PR-
113 PM AST Wed Apr 30 2025

...A STRONG THUNDERSTORM WILL IMPACT VILLALBA...COAMO...SANTA
ISABELA...JUANA DIAZ...SANTA ISABEL AND WESTERN AIBONITO
MUNICIPALITIES THROUGH 215 PM AST...

At 111 PM AST, Doppler radar was tracking a strong thunderstorm over
Coamo. This thunderstorm was nearly stationary.

HAZARD...Wind gusts up to 40 mph.

SOURCE...Radar indicated.

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

Locations impacted include...
Coamo, Villalba, Pastos, Mariano Colon, Las Ollas, Los Llanos, El
Ojo, Santa Isabel, Parcelas Penuelas, Jauca, Aibonito, and Palmarejo.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 1817 6652 1818 6629 1808 6624 1804 6631
      1803 6631 1799 6634 1798 6634 1795 6641
TIME...MOT...LOC 1711Z 347DEG 3KT 1808 6637

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

CAM