570
FXUS66 KSGX 310353
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
853 PM PDT Sat Aug 30 2025

.SYNOPSIS...
Warm and dry under sunny skies through the weekend. Heat peaks
Monday and Tuesday with some inland areas under a Heat Advisory.
Monsoonal moisture returns for Tuesday into the end of next week,
with chances for showers and thunderstorms in the mountains and
deserts each afternoon.

&&

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

Drier conditions today allowed temperatures in the mountains and
deserts to be generally higher than yesterday while a stronger sea
breeze kept temperatures in the coastal areas lower than
yesterday. Cumulus clouds developed over the mtns again this
afternoon but skies are currently clear. Chances are better than
last night for marine layer low clouds to return to the coastal
areas late tonight.

From previous discussion...
Temperatures will continue to climb into early next week as an
elongated ridge over the central CONUS amplifies, with the thermal
ridge axis setting up over the Colorado River Valley. By Monday,
850mb temps of 28-30C over the region should usher in highs of
110-112F for the deserts and 100-106F for the Inland Empire. The
lack of a widespread marine layer yesterday and today has resulted
in warmer than expected temperatures across the valleys and
coastal regions, with limited cooling overnight due to the
stubborn monsoonal moisture left over from the past week. With the
building ridge, any return of the marine layer will be patchy at
best, and limited to near or just off the coast into early next
week. Given the expected patchiness, no widespread dense fog is
currently expected, but localized areas of visibility below 2
miles won`t be out of the question.

Heat will peak Monday/Tuesday with temperatures 6-12 degrees above
normal across valleys and coastal terrain/foothills, and a Heat
Advisory is in effect for these areas. By Tuesday, monsoonal
moisture will surge northward into the mountains and deserts,
limiting temperatures a bit for these regions. With ample mid-
level moisture and instability, showers and thunderstorms could
develop off the mountains Tuesday afternoon, similar to what was
observed this past week. A few storms will likely make it off the
mountains and into the urban parts of the Coachella Valley, with a
lower chance for spillover into the Inland Empire or San Diego
valleys. Brief, heavy rainfall, lightning, and very gusty winds
will all be possible near any storm.

The monsoonal moisture may hang around for a bit as a low off the
coast of San Francisco moves inland on Wednesday and a deepening low
over the Great Lakes pinch the ridge, breaking it down a bit but
maintaining high pressure over the region through the end of the
week. Global models continue to favor storms in the mountains each
afternoon Wednesday through Friday, but lesser confidence in
widespread storms or spillover into the urban regions. There is
substantial disagreement on the long-term pattern for the end of the
week and into next weekend, with the placement of the ridge
likely to determine temperatures and moisture surges/thunderstorm
chances across the deserts and mountains into the weekend. For
now, temperatures look to cool a bit from their peak on
Monday/Tuesday with both moisture and mid-level cloud cover
limiting afternoon heating. Have maintained at least slight
chances for thunderstorms each afternoon in the mountains into the
weekend.

&&

.AVIATION...
310245Z...VFR through this evening region-wide. SCT-BKN low clouds
based 600-1000ft MSL start to develop along the SD county coast
after 08z Sunday and push up to 5 miles inland after 12z. 30-40%
chance BKN cigs along the Orange County coastline. Low clouds that
manage to develop will retreat back to the coast by 16-17z Sunday.

&&

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

&&

.BEACHES...
A long-period (15-16 sec) southerly swell (180-200 degrees) will
bring elevated surf through Tuesday, gradually subsiding
thereafter. Surf of 3-6 feet with occasional sets to 7 feet for
south-facing beaches. Longshore currents along west-facing
beaches. High rip current risk for all beaches. Beach Hazard
Statement in effect through late Monday.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement through Monday evening for Orange County
     Coastal Areas-San Diego County Coastal Areas.

     Heat Advisory from 10 AM Monday to 6 PM PDT Tuesday for Orange
     County Inland Areas-San Bernardino and Riverside County
     Valleys-The Inland Empire-San Diego County Valleys-Santa
     Ana Mountains and Foothills.

PZ...None.

&&

$$

PUBLIC...PG
AVIATION/MARINE/BEACHES...KW