775
FGUS76 KSGX 012240
ESFSGX

Hydrologic Forecast for Extreme Southwestern California
National Weather Service San Diego CA
340 PM PDT Mon Sep 1 2025

...Flash Flood Potential Index for Extreme Southwestern California...

.SYNOPSIS...
Dry weather will continue this afternoon. An upper level inverted
trough with associated mid and upper level moisture will lift
north across the area early Tuesday morning through Tuesday night.
This will bring widespread showers and a 15-30% chance of
thunderstorms, with the highest chances Tuesday afternoon over the
mountains and deserts. Rainfall rates will generally be 0.50
inch/hour or less, with the potential for isolated rates up to
around 1.00 or more inch/hour in stronger thunderstorms should
sufficient daytime heating occur.

The wave and deeper layer moisture move out of the area by
Wednesday with more typical afternoon showers/thunderstorms
primarily across the mountains and deserts, a few of which could
drift into the inland valleys.


$$

CAZ048-050-021330-
San Bernardino and Riverside County Valleys-The Inland Empire-
San Diego County Valleys-
Including the cities of Riverside, San Bernardino, Ontario,
Moreno Valley, Fontana, Rancho Cucamonga, Corona, Escondido,
El Cajon, San Marcos, La Mesa, Santee, and Poway
340 PM PDT Mon Sep 1 2025

.TONIGHT...None...no flash flooding is expected.
.TUESDAY...Moderate...thunderstorms are expected to develop and
isolated flash flooding is possible.
.WEDNESDAY...Low...the risk of flash flooding is minimal.

$$

CAZ058-062-021330-
San Diego County Mountains-San Diego County Deserts-
Including the cities of Julian, Pine Valley, and Borrego Springs
340 PM PDT Mon Sep 1 2025

.TONIGHT...None...no flash flooding is expected.
.TUESDAY...Moderate...thunderstorms are expected to develop and
isolated flash flooding is possible.
.WEDNESDAY...Moderate...thunderstorms are expected to develop and
isolated flash flooding is possible.

$$

CAZ055-056-060-021330-
San Bernardino County Mountains-Riverside County Mountains-
Apple and Lucerne Valleys-
Including the cities of Crestline, Lake Arrowhead, Big Bear City,
Big Bear Lake, Running Springs, Wrightwood, Idyllwild-Pine Cove,
Victorville, Hesperia, Apple Valley, and Lucerne Valley
340 PM PDT Mon Sep 1 2025

.TONIGHT...None...no flash flooding is expected.
.TUESDAY...Moderate...thunderstorms are expected to develop and
isolated flash flooding is possible.
.WEDNESDAY...Moderate...thunderstorms are expected to develop and
isolated flash flooding is possible.

$$

CAZ061-065-021330-
Coachella Valley-San Gorgonio Pass near Banning-
Including the cities of Indio, Palm Springs, Cathedral City,
Palm Desert, Palm Desert Country, La Quinta, and Coachella
340 PM PDT Mon Sep 1 2025

.TONIGHT...None...no flash flooding is expected.
.TUESDAY...Moderate...thunderstorms are expected to develop and
isolated flash flooding is possible.
.WEDNESDAY...Moderate...thunderstorms are expected to develop and
isolated flash flooding is possible.

$$

CAZ043-057-552-554-021330-
San Diego County Coastal Areas-Santa Ana Mountains and Foothills-
Orange County Coastal Areas-Orange County Inland Areas-
Including the cities of Oceanside, Vista, Carlsbad, Encinitas,
Chula Vista, National City, San Diego, Huntington Beach,
Costa Mesa, Newport Beach, Laguna Beach, San Clemente, Santa Ana,
Anaheim, Garden Grove, Irvine, Orange, Fullerton,
and Mission Viejo
340 PM PDT Mon Sep 1 2025

.TONIGHT...None...no flash flooding is expected.
.TUESDAY...Low...the risk of flash flooding is minimal.
.WEDNESDAY...None...no flash flooding is expected.

$$