614
FXUS66 KSGX 200948
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
248 AM PDT Wed Aug 20 2025

.SYNOPSIS...
High pressure across the southwest states will continue the
warming trend with the heat peaking on Thursday and Friday. This
will be followed by a gradual cooling trend with temperatures
returning to around average on next Tuesday. Monsoonal moisture
will begin to increase on Thursday with chances for afternoon and
early evening showers and thunderstorms for the mountains and
deserts beginning on Friday and continuing into next week.

&&

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

.SHORT TERM (Today through Friday)...
High pressure over the Great Basin and southwest states will
continue the warming trend with the heat peaking for most areas on
Thursday and Friday. High temperatures on Thursday and Friday will
range from a few degrees above average for coastal areas to 5 to
10 degrees above average for inland areas. High temperatures on
Thursday and Friday will range from the mid 70s to lower 80s near
the coast to the upper 90s to 108 for the Inland Empire and high
desert with 112 to 116 for the lower deserts.

Extreme Heat Warnings and Heat Advisories continue for all but
coastal areas for at least a portion of today through Saturday and
are in effect for all of those areas on Thursday and Friday.

The most likely locations to near or exceed daily records for
high temperatures and warmest overnight low temperatures are in
the mountains for Thursday and Friday. There are additional
locations, most in the Inland Empire and lower deserts, that could
tie or exceed warmest overnight low temperatures at times for
Friday into early next week.

Chances for Palms Springs to tie or set new daily records for
warmest overnight low temperatures are greater for Friday through
Sunday. Chances are greatest on Saturday with an 83 percent
chance of tying or exceeding the current warmest low temperature
record of 86 and and 80 percent chance of exceeding that record.

The marine layer will remain around 1200 feet deep with night and
morning coastal low clouds and fog spreading into coastal areas
and occasionally the far western valleys late each night.

Monsoonal moisture is expected to begin increasing on Thursday
with the increase continuing into the weekend. Chances for any
measurable rainfall for the mountains remains below 15 percent on
Thursday. Chances for mainly afternoon and early evening showers
and thunderstorms, mainly for the mountains and deserts, will
increase on Friday into the weekend and continue into early next
week. Daily chances for measurable rainfall at Big Bear exceed 50
percent each day for Friday through Monday, but with daily chances
for one-half inch or more of rainfall each day below 20 percent.

&&

.LONG TERM (Saturday through Tuesday)...
There will be a gradual cooling trend for Saturday through Tuesday
with Tuesday high temperatures returning to around average. High
temperatures for next Tuesday will range from the lower to mid 70s
near the coast to the upper 80s to upper 90s for the Inland Empire
with 102 to 106 for the lower deserts.

Chances for measurable rainfall from mainly afternoon and early
evening showers and thunderstorms are greatest over the weekend
and mostly for the mountains and deserts with gradually decreasing
chances through the middle of next week.

&&

.AVIATION...
200855Z...Coast/Valleys...Patchy low clouds 500-800 ft MSL along the
San Diego County coast will continue to become more widespread and
continue north into Orange County, with a 40% chance for cigs at
KSNA by 12Z. Vis reductions 1-4 SM over coastal mesas. Low clouds
expected to scatter out 15-17Z. Similarly based, patchy low clouds
will form late tonight, with a 45% chance for cigs at KSAN by 21/15Z.

Mountains/Deserts...VFR conditions prevailing through tonight with
high clouds ~15-20k ft MSL.

&&

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

&&

.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 this morning to 8 PM PDT Saturday for
     San Bernardino and Riverside County Valleys-The Inland
     Empire.

     Heat Advisory from 10 AM this morning to 8 PM PDT Friday for
     Riverside County Mountains-San Bernardino County Mountains-
     San Diego County Mountains-San Diego County Valleys.

     Heat Advisory from 10 AM Thursday to 8 PM PDT Friday for Orange
     County Inland Areas-Santa Ana Mountains and Foothills.

     Extreme Heat Warning from 10 AM this morning to 8 PM PDT
     Saturday for Apple and Lucerne Valleys-Coachella Valley-San
     Diego County Deserts-San Gorgonio Pass near Banning.

PZ...None.

&&

$$

PUBLIC...17
AVIATION/MARINE...CSP