912
FXUS66 KSGX 231012
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
312 AM PDT Sat Aug 23 2025

.SYNOPSIS...
High temperatures will remain above average through Monday, but
with slight inland cooling today. High temperatures will cool to a
few degrees below average for Tuesday through Friday. Greater
monsoonal moisture will remain in place through Tuesday with
chances for afternoon and early evening showers and thunderstorms
each day, mainly for the mountains and deserts. There will be
drying of the monsoonal moisture for Wednesday through Friday with
decreasing thunderstorms chances each day. Night and morning low
clouds will mostly be limited to coastal areas through the
weekend, but could return to the western valleys for the latter
half of next week.

&&

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

.SHORT TERM (Today through Monday)...
Greater monsoonal moisture will remain in place through Tuesday
followed by gradual drying for Wednesday through Friday. There
will be greater chances for afternoon and early evening showers
and thunderstorms, mostly for the mountains and deserts each day
through Tuesday. Daily chances for one-half inch or more of
rainfall at Big Bear are generally between 15 and 20 percent each
day. There could also be some elevated convection through this
mornign with showers and isolated thunderstorms, mainly for the
mountains, deserts, and inland valleys.

High temperatures for today will be a few degrees cooler than
Friday for inland areas with not much change on Sunday and slight
additional cooling on Monday with high temperatures remaining
above average through Monday.

The marine layer will remain near 1200 to 1500 feet deep through
Monday with night and morning low clouds over the coastal waters
spreading locally inland along the coast through the weekend, then
possibly into the far western valleys for early Monday.

&&

.LONG TERM (Tuesday through Friday)...
Model guidance is generally less aggressive in showing an
additional influx of moisture on Tuesday including lower level
moisture into the lower deserts. This will be followed by gradual
decreasing monsoonal moisture for Wednesday through Friday and
decreasing chances for afternoon and early evening showers and
thunderstorms for the mountains and deserts each day.

High temperatures on Tuesday will be cooler with high temperatures
mostly a few to around 5 degrees below average for Tuesday through
Friday. High temperatures will range from the 70s near the coast
to the 90s for the Inland Empire with 102 to 106 for the lower
deserts.

The marine layer may deepen to around 1500 feet with night and
morning coastal low clouds spreading into the western valleys late
each night for the latter half of the week.

&&

.AVIATION...
230900Z...Coast/Valleys...Patchy low clouds currently based 600-1000
ft MSL will continue to develop along the coast and spread locally 5-
10 miles inland by 12Z. CIGs will lower to 500-800 ft MSL with vis 3-
6 SM, locally 0-2 SM over higher coastal terrain. Low clouds and fog
clearing over land 15-17Z this morning. Low clouds will similarly be
localized and patchy tonight, developing after 24/09Z.

Chances for stray TSRA/SHRA moving in from the east between 10-18Z
this morning, highest (15-25%) in inland valleys with 10-20% chance
for western valleys and coastal areas.

Mountains/Deserts...15-25% chance of SHRA/TSRA 10-18Z as remnant
storms move in from the east, then 35-50% of TSRA developing over
the mountains and deserts this afternoon 19-05Z. CB bases near 12
kft with tops to 35 kft. SHRA/TSRA could bring restricted VIS down
to 1-3 SM at times, along with gusty and erratic winds, cloud-to-
ground lightning, and small hail. Otherwise variable mid and high
clouds at/above 15,000 ft MSL through this evening.

&&

.MARINE...
There is a 15-20% chance of showers and a 5-10% chance of
thunderstorms to move west over the coastal waters this morning
through about 11 AM. The main threats with any thunderstorms will be
cloud-to-water lightning and locally gusty winds. Otherwise, no
hazardous marine conditions are expected through Wednesday.

&&

.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 this evening for Orange County
     Inland Areas-San Bernardino and Riverside County Valleys-
     The Inland Empire-San Diego County Valleys-Santa Ana
     Mountains and Foothills.

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

PZ...None.

&&

$$

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