FXUS66 KSGX 240422
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
922 PM PDT Tue Jul 23 2024

.SYNOPSIS...
After an active afternoon in the mountains and deserts Tuesday, a
drying trend will start Wednesday and continue through the weekend.
A few showers and thunderstorms are expected to develop in the
mountains and High Desert Wednesday afternoon, with decreasing
chances Thursday through the weekend. Otherwise, hot conditions will
continue in the valleys, mountains, and deserts through the end of
the work week. Cooler conditions expected over the weekend with
increased coastal low cloud coverage.

&&

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

Low clouds may be slow to develop tonight, with patchy coverage
possible along the coast late tonight into early Wednesday morning.
Low clouds should clear quickly, leaving mostly sunny skies until
cumulus clouds develop over the mountains late in the morning. Any
shower or thunderstorm development on Wednesday will be isolated in
coverage and confined to the mountains and High Desert. Hot
conditions will continue through Thursday for the valleys and
mountains, potentially continuing into Friday for the deserts.
Cooler conditions are expected for all areas over the weekend into
early next week.

From previous discussion issued at 2 PM Tue July 23...

The moisture in place will start to decrease on Wednesday as the
mean flow veers to south. Still thunderstorms in the mountain spine
but less coverage. This becomes southwest steering flow on Thursday
as the upper high over Nevada shifts east and an upper trough short
wave crosses Norcal on Friday. This will lead to strong drying on
Thursday and increased onshore flow on Friday. The drying and little
change to the air mass on Thursday will lead to warming for most
areas especially inland. Thursday should be the hottest day of the
week for most areas. Only isolated cells on Thursday that shift into
the High Deserts and lower desert slopes due to the southwest flow
increasing. The air mass remains as hot for the lower deserts on
Friday so heat warning may need to be extended into Friday there.

For the weekend there is a cooler air mass from the system passing
to the north for notably less heat in Socal and more extensive
marine layer.

&&

.AVIATION...
240400...Coast/Valleys... Satellite shows low clouds about 40 miles
offshore, and confidence is decreasing for CIGs developing at
coastal sites this evening. Chances for CIGs by 24/15z at KCRQ is
about 30%-50%, with lower than 30% chance for KSAN and KSNA. Patchy
FG/HZ will be possible overnight with VIS down to 5SM for the higher
coastal terrain and valleys. If CIGs do develop for coastal sites,
bases of 800-1100 with tops to 1700, and clearing should occur by
24/16z.

Mountains/Deserts...TSRA will be possible in the mountains late
Wednesday morning through Wednesday afternoon. Some storms may make
it off the mountains and into the deserts. Lightning and erratic
winds near any storm, with SCT-BKN Cu and bases to 12,000 ft MSL.
Mod to strong up/downdrafts near the mountains. Confidence in TSRA
impacts at TAF sites too low to include mention at this time.

&&

.MARINE...
No hazardous marine conditions are expected through Saturday.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 10 PM PDT Thursday for Riverside County
     Mountains-San Bernardino County Mountains-San Bernardino
     and Riverside County Valleys-The Inland Empire-San Diego
     County Mountains-San Diego County Valleys.

     Excessive Heat Warning until 10 PM PDT Thursday for Apple and
     Lucerne Valleys-Coachella Valley-San Diego County Deserts-
     San Gorgonio Pass Near Banning.

PZ...None.

&&

$$

PUBLIC...CO/Tardy
AVIATION/MARINE...Zuber