735
FXUS66 KSGX 220434 CCA
AFDSGX

Area Forecast Discussion...CORRECTED
National Weather Service San Diego CA
934 PM PDT Thu Aug 21 2025

.SYNOPSIS...
Warmer than average conditions will continue through the weekend.
There are chances of showers and thunderstorms over the mountains
and deserts each afternoon and evening Friday through the middle of
next week. The marine layer will be very thin, leading to minimal
clouds and fog through Saturday with better cloud coverage near the
coast by early next week. By the end of next week, cooler conditions
return with lesser chances of thunderstorms.

&&

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

Areas of high clouds are expected to continue overnight. If any low
clouds develop, they will be patchy in coverage and limited to
coastal areas. The 00Z sounding from KNKX was showing an increase in
precipitable water, at 1.42 inches, which is up from just over an
inch on Thursday morning`s. Precipitable water is expected to
continue to increase into Friday and remain elevated through the
weekend and into early next week. Shower and thunderstorm chances
remain in the forecast each day through the middle of next week
for the mountains and deserts. No changes to the forecast this
evening. High temperatures for Friday are expected to be very
similar to Thursday`s.

From previous discussion issued at 2 PM August 21, 2025...

Hot conditions will continue into Friday as the high pressure peaks
in intensity. Friday will see an increase in monsoonal moisture
which will make it feel more humid, especially across the lower
deserts. Chances for storms increase across the mountains and
locally into the deserts by Friday afternoon. Elevated convection is
seen on local hi-res models Friday night into Saturday, which may
produce some light showers across this region. These showers may
maintain themselves into valleys west of the mountains, mainly the
Inland Empire. Saturday and Sunday afternoon will see daily storm
chance across the mountains and deserts. Rain rates through the
weekend are low to moderate confidence, but most rates will be near
one quarter to one half inch per hour.

Confidence lowers on exact mountain and desert locations will see
shower and storm activity, but chances remain 20-50% per NBM through
Wednesday. High pressure will weaken through early next week,
prompting temperatures to lower near average. Ensemble models show a
continued weakening of this area of high pressure along with a
trough that may form offshore. This trend would lead to a further
cooling trend and lower chances for thunderstorm activity.

&&
.AVIATION...
220330Z...Coast/Valleys...At this time, skies continue to remain
mostly clear and are still struggling to form over the inner
coastal waters at this hour. Low clouds and fog return to the
immediate coast 09Z-16Z Friday with about a 30 percent chance for
CIG/VIS impacts at KSAN and 10-20 percent chance at KCRQ and KSNA.
Expect clearing to the beaches by 17Z Friday. Tomorrow evening
will likely be very similar, with lack in low cloud coverage.

Mountains/Deserts...SCT-BKN clouds 15-20kft MSL through tonight.
TCU/CB formation with bases around 7-9kft MSL is expected with
during the afternoon hours over the mountains and deserts; with
around a 30-40% probability over the mountains, and a 10-20% for
the deserts. With this, there could be temporary SHRA/TSRA with
restricted VIS down to 1-3SM, at times, along with gusty and
erratic winds, dangerous cloud-to-ground lightning, and possibly
some small hail.

&&

.MARINE...
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 Friday 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...CO/APR
AVIATION/MARINE...Stewey