518
FXUS66 KSGX 171540
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
840 AM PDT Tue Jun 17 2025

.SYNOPSIS...
High pressure to the south will maintain above average high
temperatures through Wednesday, as much as 10 to 15 degrees above
average for the deserts. This will be followed by a cooling trend
for Thursday into the weekend with Sunday high temperatures as
much as 10 to 15 degrees below average for the mountains and
inland valleys. Night and morning coastal low clouds and fog will
spread farther into the valleys for the weekend as the marine
layer deepens for Thursday into the weekend. Not much change for
early next week.

&&

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

.Morning Update...

Low clouds will continue to clear out of coastal areas of Orange
County and near Camp Pendleton this morning for mostly sunny
conditions across the CWA through the afternoon and evening. High
pressure over Baja California will begin to amplify over the
Desert Southwest, bringing continued hot weather away from the
coast. High temperatures will be near 5 to locally above 10
degrees above normal. Hottest temperatures across the high desert
will be felt on Wednesday with moderate to high confidence in
seeing temperatures near 105 degrees. Slow cooling will occur by
Thursday and Friday with more noticeable cooling by the weekend
with dry weather continuing for the foreseeable future.

.Previous Discussion (353 AM Tuesday)...

SHORT TERM (Tuesday through Thursday)...
The NKX sounding for late Monday afternoon showed that the marine
layer was around 400 feet deeper than late Sunday afternoon with
high temperatures for the coast and valleys on Monday not quite
as hot as on Sunday. The marine layer is expected to fluctuate
between 1000 and 1500 feet deep through Wednesday with night and
morning coastal low clouds and fog extending into the far western
valleys at times.

Through Wednesday, high temperatures will remain around 5
degrees above average near the coast to 10 to 15 degrees above
average for the deserts. High temperatures through Wednesday will
range from the lower 70s near the coast to the 90s for the Inland
Empire with 112 to 117 for the lower deserts.

For Thursday into the weekend, a low pressure system moving from
the eastern Pacific into the western states will weaken the high
pressure aloft over southern California and strengthen the onshore
lower-level flow. High temperatures on Thursday will cool to
around average near the coast to 5 to 10 degrees above average for
the deserts.

&&

.LONG TERM (Friday through Monday)...
The cooling trend will continue into the weekend with the coast
and valleys coolest on Saturday and the deserts on Sunday. High
temperatures on Sunday will range from a few degrees below average
near the coast to 5 to locally 10 degrees below average inland.
High temperatures on Sunday will range from around 70 near the
coast to the upper 70s to upper 80s for the Inland Empire with
around 100 for the lower deserts. The marine layer will deepen to
1500 to 2000 feet with night and morning coastal low clouds
spreading farther into the valleys. Not much change is expected
for early next week.

&&

.AVIATION...
171530Z....Coast/Western Valleys...Mostly clear skies through the
evening. Areas of low clouds will develop after 05Z with bases 500-
800 feet MSL and vis 3-5SM in BR, but locally 0-2SM on higher
terrain. Scatter out Wednesday 14-16Z.

.Inland Valleys/Mountains/Deserts...Clear skies and unrestricted VIS
through Wednesday morning.

&&

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

.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 Wednesday for Riverside County
     Mountains-San Bernardino and Riverside County Valleys-The
     Inland Empire-San Diego County Mountains-San Diego County
     Valleys.

     Heat Advisory until 8 PM PDT this evening for Orange County
     Inland Areas-Santa Ana Mountains and Foothills.

PZ...None.

&&

$$

UPDATE...APR
PUBLIC...17
AVIATION/MARINE...MM