827
FXUS66 KSGX 210707
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
1207 AM PDT Tue Jul 21 2026

.SYNOPSIS...
There will be slow inland warming through Wednesday. There will
be greater warming on Thursday with widespread moderate to locally
major HeatRisk for Thursday through the weekend for the mountains
below 6500 feet, the inland valleys, inland Orange County, and
the Apple and Lucerne Valleys with major to locally extreme
HeatRisk for the lower deserts. There is a slight chance of
showers for the mountains on Thursday afternoon and a slight
chance of showers and thunderstorms for the mountains on Friday
afternoon. Night and morning coastal low clouds will spread into
the far western valleys at times late each night.

&&

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

.SHORT TERM (Today through Thursday)...
There will be drying of monsoonal moisture for today and
Wednesday, an increase for Thursday into Friday, then a greater
decrease for the weekend into early next week. For this afternoon
and Wednesday afternoon, there will just be some clouds over the
mountains and maybe a few sprinkles. A slight chance of showers
will return for Thursday afternoon. The marine layer will remain
around 1500 feet deep with night and morning coastal low clouds
spreading into the far western valleys at times late each night.

High temperatures for today and Wednesday will be a few degrees
cooler for areas near the coast into the San Diego County valleys.
For the mountains, deserts, and inland valleys, high temperatures
will warm a few degrees today and a few to around 5 degrees on
Wednesday. High temperatures on Wednesday will be within a few
degrees of average for most areas, ranging from the mid to upper
70s near the coast to the 90s for the Inland Empire with 108 to
112 for the lower deserts.

There will be greater warming on Thursday of a few degrees near
the coast to around 4 to 8 degrees for inland areas with the
greatest warming for the mountains and inland valleys. High
temperatures on Thursday will be few degrees above average near
the coast to around 4 to 8 degrees above average for inland areas.
High temperatures on Thursday will range from the mid 70s to
around 80 near the coast to the mid 90s to 107 for the Inland
Empire with 112 to 116 for the lower deserts.

For Thursday into the weekend, there will be widespread moderate
HeatRisk for the mountains below 6500 feet, for the inland
valleys, inland Orange County, and the Apple and Lucerne Valleys
with widespread major HeatRisk for the lower deserts.

Beginning on Wednesday, there is an Extreme Heat Watch for the
deserts and a Heat Advisory for the mountains, valleys, and
inland Orange County, though the greater heat and HeatRisk will
begin on Thursday.

&&

.LONG TERM (Friday through Monday)...
Not much change in high temperatures is expected through Sunday
with high temperatures a few degrees cooler possible on Monday.
An increase in moisture and some mid and high clouds for Thursday
night will result in low temperatures a few to around 5 degrees
warmer than Wednesday night with a corresponding slight increase
in HeatRisk on Friday. For Friday for the mountains below 6500
feet, inland valleys, and Apple and Lucerne Valleys, the HeatRisk
will increase to moderate to locally major with the HeatRisk for
the lower deserts increasing to major to locally extreme.

There is a slight chance of showers and thunderstorms for the
mountains on Friday afternoon followed by drying for the weekend
into early next week.

&&

.AVIATION...
210500Z....Coast/Valleys...FEW-BKN mid-high level (12-15 kft) clouds
this evening, significantly limiting low cloud formation for most of
the evening. Very patchy low clouds (~1000-1500 ft MSL bases)
expected to form near the coast after 08z, yielding very
intermittent low cloud cigs to the coastal TAF sites, if any. Chance
for over 1hr of MVFR/IFR cigs tonight: 50% for KSAN (09-14z), 40%
for KCRQ (10-13z) and 20% for KSNA (11-14z). Remaining patchy clouds
scatter out 14-16z Tue, then VFR conditions prevail with FEW-SCT mid
level clouds through Tuesday evening.

Mountains/Deserts...SCT-BKN clouds 12-15 kft MSL. West winds gusting
15-25 kts along desert slopes and up to 35 kts through the Banning
Pass expected through 07z Tue, then once again after 00z Wed.

&&

.MARINE...
There is a 75% chance for NW wind gusts to exceed 20 kts in the
outer waters near San Clemente Island both Wednesday and Thursday
afternoons. Additionally, a mixed swell will cause steep and choppy
seas during the day Thursday, especially in the outer waters.

&&

.BEACHES...
Southerly swell of 4-5 ft with a period of 11-13 seconds will
continue to bring elevated to high surf and strong rip and longshore
currents through Tuesday. Surf 4-7 feet with sets to 8 feet is
expected through Tuesday, with the highest surf focused on south and
southwest facing beaches of Orange County. A High Surf Advisory
remains in effect until 11 PM Tuesday.

The southerly swell and surf falls through the day on Tuesday,
remaining lower into Wednesday. Another round of elevated southerly
swell from a tropical cyclone well off the coast is expected
Thursday through the end of the week. This swell is expected to be
around 4-5 ft with a period of about 15 seconds which would once
again bring high surf of 6-8 feet, especially for south-southwest
facing beaches.

&&

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

&&

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

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

     Extreme Heat Watch from Wednesday morning through Monday evening
     for Apple and Lucerne Valleys-Coachella Valley-San Diego
     County Deserts-San Gorgonio Pass near Banning.

PZ...None.

&&

$$

PUBLIC...17
AVIATION/MARINE/BEACHES...Westerink

NWS San Diego (SGX) Office