566
FXUS66 KSGX 111638
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
938 AM PDT Mon Aug 11 2025

.SYNOPSIS...
Hot inland through Tuesday with high temperatures around 5-8
degrees above normal in the mountains and deserts. Gradual cooling
Wednesday through next weekend. Night and morning low clouds will
continue along the coastal areas and far western valleys,
spreading slightly further inland later in the week as the marine
layer deepens.

&&

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

Update: Latest satellite imagery shows that most of the clouds have
now dissipated over land, with the only exception being around the
Mount Soledad area in San Diego County, which is still experiencing
some mostly cloudy to overcast skies at this moment. There could be
some of these coastal clouds hugging the coastline to move in
onshore periodically throughout the afternoon. Temperatures will
still be on the order of above average by 5 to 10 degrees,
especially within the inland areas. Expect little change to occur in
the overall pattern through the next few days, with only a slight
breakdown in the ridge and thus slightly cooler temperatures. This
cooling trend will continue into the later part of the week through
next weekend with further influence from a trough upstream over the
E Pac waters. There will be an increase in RH values, although an
increase in gusty afternoon winds as a result from this troughing,
although conditions are expected to remain dry with suppression of
the monsoonal flow east of the CWA. That being said, some mid-level
moisture over the region today could provide an isolated shower or
possible thunderstorm to form over the mountains later this
afternoon, mainly over the mountains of San Diego County.

(Original discussion submitted at 242 AM):

Low clouds are much slower to develop this morning and have yet to
spread inland across much of the coastal areas, but expect them to
move at least a few miles inland by sunrise. Elsewhere skies
remain clear. Convection over the Sonoran Desert is further east
than last night with no signs of a gulf surge in the lower desert.
There may be a modest increase in moisture in the morning as
upvalley winds develop, but this will mix out a bit quicker,
allowing for better warming in the low deserts today. Overall
highs in the mountains and deserts will be around 5-8 degrees
above normal today as an upper level high builds in from the north,
with temps closer to normal west of the mountains thanks to the
persistent marine layer. Mid-level moisture begins to decline
today, with chances of showers/thunderstorms over the mountains
less than 10%.

The upper level ridge weakens slightly on Tuesday with no
noticeable change in high temperatures. The high then shifts east
and continues to break down as an upper level trough moves inland
across the Pac NW on Wednesday, allowing for some cooling to
occur. Ensembles are in good agreement with the mean trough
amplifying along the West Coast for the latter half of the week,
bringing continued cooling to the region with high temperatures
falling to below normal Friday and Saturday - as much as 10
degrees below normal in the valleys. The marine layer will gradual
deepen for the second half of the week as well with low clouds
extending slightly further into the valleys during the nights and
mornings. The upper level high begins to strengthen over the
Desert Southwest early next week for a return of warmer weather.

No signs of monsoon moisture for the remainder of the week with
the forecast remaining dry. Most members of the GEFS and EPS show
moisture returning sometime around the 20th, but that 10+ day
forecast has been advertised many times this summer and rarely
materialized, so don`t count on it just yet.

&&

.AVIATION...
111530Z...Coasts/Valleys...Low clouds with bases 500-900 feet MSL
and vis 3-5SM near higher coastal terrain will continue to scatter
out through 17Z. Low clouds to redevelop and move ashore after 05Z,
moving locally into western valleys overnight into Tuesday.
Bases will be 700-1000 ft MSL, locally down to 300-500 ft MSL, and
vis down to 2-4 SM near higher coastal terrain.

Mountains/Deserts...Mostly clear and VFR conditions through tonight,
except for a few cumulus clouds at 10000 feet MSL over mountain
peaks 18-01Z.

&&

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

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 8 PM PDT this evening 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.

&&

$$

UPDATE...Stewey
PUBLIC...SS
AVIATION/MARINE...CO