912
FXUS66 KSGX 072330
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
430 PM PDT Mon Sep 7 2026

.SYNOPSIS...
Scattered light rain possible through the afternoon. An isolated
thunderstorm or two cannot be ruled out today. Hot conditions
expected for the middle to end of the work week, resulting in areas
of moderate to major HeatRisk. Slight chance of mountain showers and
thunderstorms Tuesday and Wednesday. Gradual cooling for the
weekend.

&&

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


...UPDATED AVIATION DISCUSSION...

Radar reflectivity has been quite active this morning, with
consistent returns across the area north of San Diego County. It`s
likely the majority of that precipitation is not actually reaching
the ground with only an additional 0.01-0.08 inches of rain
recorded since 4 AM. Light rain is possible through the rest of
the day, with accumulations expected to be light and scattered in
nature. An isolated thunderstorm or two cannot be ruled out, most
likely for the coast, valleys, and mountains north of San Diego
County and in the High Desert.

High cloud coverage continues to be widespread today, but is
expected to thin out tomorrow. Precipitable water values are
expected to remain elevated which will keep overnight lows elevated
and conditions feeling tropical. The tropical feeling airmass is
expected to disrupt marine layer low cloud and fog development
and may result in a weaker afternoon sea breeze. This will
contribute to high and low temperatures along the coast running 10
to 15 degrees above average. Further inland, daytime highs will
be 5 to 10 degrees above average with a more notable increase in
low temperatures which are expectd to run 8 to 15 degrees above
average. Hottest conditions are expected Tuesday through Thursday
for the coast, valleys, and mountains below 5000 ft with hottest
conditions expected in the low desert Wednesday through Friday.
Widespread moderate to areas of major HeatRisk are expected.

The lingering moisture and increased sunshine for Tuesday and
Wednesday will increase chances of afternoon showers and
thunderstorms over the mountains. There is expected to be little to
no additional forcing outside of the usual diurnal heating so
coverage of any thunderstorms should be fairly isolated. By
Thursday, a transient ridge of high pressure is expected to move
directly over Southern California. This would result in an airmass
likely too stable for thunderstorm development, although with
lingering moisture in the air a few showers cannot be ruled out over
the mountains.

There is a spread in potential outcomes for the upper level pattern
over the upcoming weekend. 32 percent of ensemble solutions have a
trough over the Pacific Northwest, which would bring noticeable
relief from the heat and humidity. 17 percent of solutions keep the
ridge overhead which would prolong the heat event. The rest of the
solutions are somewhere in between, with a slower passage of the
trough but a weakening of the ridge. Current forecast follows the
NBM and is more inline with the "in between" solutions with a
gradual decrease in both high and low temperatures Friday through
Sunday.

&&

.AVIATION...
080000Z...VFR conditions expected across the region through Tuesday
morning. SCT-BKN high clouds around 10-20 kft will continue through
most of Tuesday. ISO-SCT -SHRA/localized TSRA will continue for San
Diego Co mtns and deserts + areas north of San Diego County for the
next few hours, tapering off around 03Z.

Mtns/Desert Foothills...Good chance for ISO -SHRA and TSRA (20-40%
chance for any one area) again over inland mtns into the desert
foothills 20Z Tue through 03Z Wed. Brief heavier precip, localized
gusty winds, and lightning possible in storms.

&&

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

&&

.BEACHES...
A large south swell from Hurricane Marie will continue to produce
large surf of 4 to 7 feet, with sets up to 10 feet this morning,
highest on south and southwest facing beaches. This will result in
elevated to high surf and strong rip and longshore currents,
creating hazardous swimming conditions. Additionally, high tides
during the evenings will combine with the high surf to produce minor
tidal overflow, coastal flooding, and localized beach erosion. Swell
and surf will gradually diminish tonight through Tuesday night.
Check the Coastal Hazard Message for details.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Coastal Flood Advisory until 11 PM PDT Tuesday for Orange County
     Coastal Areas-San Diego County Coastal Areas.

     High Surf Advisory until 11 PM PDT Tuesday for Orange County
     Coastal Areas-San Diego County Coastal Areas.

     Heat Advisory from 10 AM Tuesday to 8 PM PDT Thursday for Orange
     County Coastal Areas-Orange County Inland Areas-Riverside
     County Mountains-San Bernardino and Riverside County
     Valleys-The Inland Empire-San Diego County Coastal Areas-
     San Diego County Mountains-San Diego County Valleys-Santa
     Ana Mountains and Foothills.

     Extreme Heat Warning from 10 AM Wednesday to 8 PM PDT Friday for
     Coachella Valley-San Diego County Deserts-San Gorgonio Pass
     near Banning.

PZ...None.

&&

$$

PUBLIC...CO
AVIATION/MARINE/BEACHES...CSP