010
FXUS66 KSGX 242046
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
146 PM PDT Mon Aug 24 2026

.SYNOPSIS...
Monsoonal moisture will maintain a slight chance of afternoon
showers and thunderstorms for the mountains and deserts through
Tuesday. A warming trend will continue through Thursday with
widespread major to extreme HeatRisk for the lower deserts,
valleys, and inland Orange County. Widespread moderate or greater
HeatRisk except for mountain elevations above 7000 feet is
expected to continue through next Saturday.

&&

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

This morning featured clouds in all levels of the troposphere.
Patchy fog covered San Diego County west of I-15 earlier in the
morning, making way to photogenic skies of cumulus, altocumulus, and
cirrus embedded with a few virga showers (sprinkles were reported in
inland parts of San Diego). While these clouds signal to plentiful
mid-level moisture, the broad coverage in SD County might be
delaying convection over the mountains and thus shower/tstorm
activity until later in the afternoon. Meanwhile, cumulus clouds
have been persistently building on the eastern slopes of the San
Bernardino and Riverside County mountains with some showers
developing. More showers and thunderstorms are likely over these
slopes through around 7 PM this evening. Any thunderstorm that
develops could bring heavy downpours and up to an inch of rain
locally.


Temperatures this afternoon are generally running a few degrees
cooler than yesterday, expecting to reach the mid-90s inland,
100- 105F in the IE and 106-110F in the lower deserts. Highs today
are expected to be the noticeably the coolest for the week for
the inland valleys and lower deserts.

Thunderstorm chances peak this afternoon as PWAT`s fall through
Wednesday, though isolated terrain driven shower/t-storm chances
remain in the forecast for our mountains through Thursday as the mid-
level flow remains southerly, tapping into modest mid-level
moisture.

The ridge axis over the Desert Southwest shifts westward through the
middle of the week and high temperatures peak Wednesday through
Friday through Southern California. Highs are expected to reach the
upper 90s to 105F in the inland valleys, 103-108F through the IE and
up to 115F in the lower deserts.

Both the GFS and the ECMWF show a significant flattening of the
ridge over the weekend, increasing confidence that temperatures will
return closer to normal by early next week.


In the meantime, take breaks in the shade, hydrate and seek A/C when
possible!

&&

.AVIATION...
241830Z...Coast...Patchy low clouds expected to develop overnight,
most likely to impact KSAN and KCRQ after 12Z. Low confidence in
cigs reaching KSNA. Vis reductions 0-5 SM possible where cigs form.
Any cigs and vis restrictions will clear around 15Z.

Mountains/Deserts...Building cumulus based around 9000 feet MSL
leading to CB clouds with tops to 45000 feet and SCT TSRA over
mountains and locally into adjacent deserts through 02Z. Any TS
could produce gusty, erratic winds.

Otherwise...SCT to locally BKN clouds AOA 20000 feet MSL becoming
mostly clear after 03Z.

&&

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

&&

.BEACHES...
A 4-5 foot southerly swell (from 170 degrees) at 13-15 seconds will
move into the area Wednesday and Thursday, leading to elevated surf
for the south facing beaches of northern San Diego County and Orange
County. Breaking waves of 4 to 6 feet expected, sets up to 8 feet
possible at beaches that face due south. Surf gradually subsides on
Friday.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory from 10 AM Tuesday to 8 PM PDT Friday for Orange
     County Coastal Areas-San Diego County Coastal Areas.

     Heat Advisory until 10 AM PDT Tuesday for Orange County Inland
     Areas-San Bernardino and Riverside County Valleys-The
     Inland Empire-San Diego County Mountains-San Diego County
     Valleys-Santa Ana Mountains and Foothills.

     Extreme Heat Warning from 10 AM Tuesday to 8 PM PDT Friday for
     Apple and Lucerne Valleys-Orange County Inland Areas-San
     Bernardino and Riverside County Valleys-The Inland Empire-
     San Diego County Mountains-San Diego County Valleys-Santa
     Ana Mountains and Foothills.

     Heat Advisory until 8 PM PDT Friday for Riverside County
     Mountains-San Bernardino County Mountains.

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

PZ...None.

&&

$$

PUBLIC...Westerink
AVIATION/MARINE/BEACHES...CO

NWS San Diego (SGX) Office