560
FXUS66 KSGX 102038
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
138 PM PDT Sun Aug 10 2025

.SYNOPSIS...
Slight chance of thunderstorms over the San Diego County Mountains
and Santa Rosa Mountains this afternoon and early evening. Hot
temperatures prevail for most locations through Wednesday before a
gradual cooling trend and a deepening marine layer helps return
temperatures to near normal by the end of the week and below normal
by the weekend.

&&

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

Low and mid level moisture filtered in yesterday and this morning
with stations currently reporting dew points in the 60s across the
Coachella Valley and desert slopes of the mountains. This moisture
has helped to shave off some of the hottest temperatures for areas
under an Extreme Heat Warning both yesterday and today, and will
be a key element for potential thunderstorms across the southern
mountains this afternoon. There is currently ample instability
across southwestern Arizona and southeastern California, and
soundings show MLCAPE values of around 1200-1800 J/kg for the San
Diego County Mountains. This, along with PWs > 1.2" may be enough
for a few thunderstorms to develop (15-30% chance) with gusty,
erratic winds, heavy rainfall, and frequent lightning all possible.
Given the diurnal nature of these storms, any precipitation
should generally end by 7PM with drier conditions expected to
prevail into the end of the week.

Other than the thunderstorm potential today, the main story remains
the unseasonable temperatures. High pressure slides down into
Central California on Monday, spreading into southeastern California
Tuesday. With drier conditions and the upper level ridging, high
temperatures across the mountains and deserts will remain hot
through Tuesday, around 5-10 degrees above normal, and heat products
remain in effect. Luckily, with the departure of the low and mid
level moisture, the deserts and mountains will be able to more
effectively cool off during the overnight hours, allowing for
some relief from the heat. By Wednesday, the ridge will begin to
breakdown and shift into the Four Corners region, with weak
troughing setting in for the end of the week. This will support a
gradual cooldown through Friday, with each day 3-5 degrees cooler
than the day before. With troughing returning, the marine layer
will deepen, spreading further inland each morning. By the
weekend, temperatures region-wide look to be 5-10 degrees below
normal.

Further troughing into early next week looks possible as a
low moves down along the coast of Canada, but newer runs have
attempted to shift high pressure back over the Desert Southwest,
possibly returning the region to a warming trend. For now,
slightly below normal temperatures are expected to prevail into at
least early week.

&&

.AVIATION...
102000Z...Coasts/Valleys...Patches of low clouds over nearshore
waters and along the beaches this afternoon. Clouds expected to
start moving inland 02-04z Mon with bases 800-1200 ft MSL, reaching
15 to 20 miles inland overnight. Low clouds are expected to scatter
out 16-18Z Mon.

Mountains/Deserts...VFR conditions continuing into Mon AM. Iso Cu
above 15,000 ft MSL over the mountains through 01Z Mon. There is a
15-30% chance of TSRA over the San Diego and Riverside County mtns
through 01Z. Gusty winds and frequent lightning near any storms.

&&

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

&&

.BEACHES...
Long period (16-17 second) southwesterly (200-220 degree) swell will
bring elevated surf and high rip current risk Monday into the
upcoming weekend. Surf of 3 to 6 feet with the highest sets along
south and southwest facing beaches.

&&

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

     Extreme Heat Warning until 8 PM PDT Tuesday for Coachella Valley-
     San Diego County Deserts-San Gorgonio Pass near Banning.

PZ...None.

&&

$$

PUBLIC...Zuber
AVIATION/MARINE/BEACHES...CO