433
FXUS66 KSGX 221042
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
342 AM PDT Fri Aug 22 2025

.SYNOPSIS...
High temperatures will remain above average through the weekend,
but with slight cooling during the weekend. There are chances for
showers and thunderstorms over the mountains and deserts each
afternoon and evening into next week with the greater chances for
Saturday through Wednesday. Night and morning coastal low clouds
will remain patchy through the weekend and limited mostly to
coastal areas.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

.SHORT TERM (Today through Sunday)...
High temperatures for today will be similar to slightly cooler
than Thursday. High temperatures on Saturday will be a few degrees
cooler with not much change on Sunday. High temperatures for today
will be around 5 to 10 degrees above average for inland areas with
Sunday high temperatures around 5 degrees above average for most
areas. High temperatures today will range from the mid 70s to
lower 80s near the coast to the upper 90s to 106 for the Inland
Empire and for the Apple and Lucerne Valleys with 110 to 114 for
the lower deserts.

The most likely locations to tie or exceed daily high temperature
records for today will be in the mountains. There are greater
chances to tie or exceed existing daily records for record warm
overnight low temperatures through the weekend for the mountains,
lower deserts, Inland Empire, and inland Orange County.

The marine layer will remain around 1200 to 1500 feet deep through
the weekend with night and morning coastal low clouds remaining
patchy and limited mainly to coastal areas.

Monsoonal moisture will increase into Saturday, then decrease
slightly on Sunday. There will be chances for afternoon and early
evening showers and thunderstorms, mostly for the mountains and
deserts each day with the greater chances on Saturday and Sunday.
There could also be some elevated convection for tonight into
Saturday morning moving along in the south to southeast flow
aloft. This could affect areas west of the mountains as well.

Any rainfall through Saturday morning is expected to be
insufficient for flash flooding. For Saturday afternoon and early
evening, thunderstorms could cause isolated flash flooding, mainly
for the San Bernardino Mountains, the Riverside County mountains,
and the Lucerne Valley. Not much change in the flash flood threat
is expected on Sunday.

&&

.LONG TERM (Monday through Thursday)...
High temperatures on Monday will be a few degrees cooler than
Sunday, mostly near to a few degrees above average on Monday. A
surge of lower level moisture into the deserts on Monday night and
Tuesday could bring greater cooling on Tuesday high temperatures
as much as 5 to 10 degrees cooler for the lower deserts.

With the additional influx of moisture, NBM daily chances for
one-half inch or more of rainfall at Big Bear increase to 30
percent on Tuesday with a 1 percent chance for one inch or more of
rainfall. Chances for mainly afternoon and early evening showers
and thunderstorms will decrease for Wednesday through the rest of
next week. High temperatures for the lower deserts should begin
to warm slowly for Wednesday and Thursday as monsoonal moisture
begins to decrease.

&&

.AVIATION...
220915Z...Coast/Valleys...Patchy low clouds and fog have formed in
areas along the coast, generally isolated to southern San Diego Co.
60% chance for impacts at KSAN 10-16Z tonight, with lower 10-20%
chances at KCRQ and KSNA. Cigs 400-800 ft MSL with vis restrictions
0-3 SM for higher coastal terrain. Clouds/fog clear to the coast 15-
17Z. Low clouds and fog forming after 23/06Z will similarly be
patchy, with a 40% chance for impacts at KSAN. Chances for stray
TSRA/SHRA moving in from the east late this evening through Sat
morning, highest (15-20%) in inland valleys with 10-15% chance for
western valleys and coastal areas.

Mountains/Deserts...SCT-BKN clouds 15-20kft MSL. TCU/CB formation
with bases around 7-9kft MSL expected during afternoon hours over
the mountains, with 30-40% probability for TSRA over the mountains,
and a 15-25% chance for the deserts this afternoon/evening. Lower
but still extant chances continue overnight into early Sat morning.
SHRA/TSRA could bring restricted VIS down to 1-3SM at times, along
with gusty and erratic winds, dangerous cloud-to-ground lightning,
and possible small hail.

&&

.MARINE...
Low (about 10% chance for nearshore waters) chance for showers or
thunderstorms to move west over the nearshore waters late this
evening through Saturday morning. Otherwise, no hazardous marine
conditions are expected through Tuesday.
&&

.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 8 PM PDT Saturday for San Bernardino and
     Riverside County Valleys-The Inland Empire.

     Heat Advisory until 8 PM PDT this evening for Orange County
     Inland Areas-Riverside County Mountains-San Bernardino
     County Mountains-San Diego County Mountains-San Diego
     County Valleys-Santa Ana Mountains and Foothills.

     Extreme Heat Warning until 8 PM PDT Saturday for Apple and
     Lucerne Valleys-Coachella Valley-San Diego County Deserts-
     San Gorgonio Pass near Banning.

PZ...None.

&&

$$

PUBLIC...17
AVIATION/MARINE...CSP