396
FXUS66 KSGX 120418
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
918 PM PDT Fri Jul 11 2025

.SYNOPSIS...
Slightly cooler conditions today and Saturday with a subtle
rebound in temperatures for Sunday and Monday. Gradual cooling
back to near average for mid July expected through the middle-end
of next week with perhaps some monsoonal moisture spreading into
the region. Night and morning coastal low clouds will spread into
the western valleys late each night.

&&

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

Update: Low level cloud bases have elevated slightly this evening
with the presence of a weak coastal eddy over the inner coastal
waters. These clouds will continue to spread inland throughout the
night and could penetrate a little further eastward tonight. Patchy
fog will be possible within some of the inland valleys as well. The
overall forecast continues to remain on track with an areas of high
pressure building over the region this weekend with a gradual warmup
through Monday, followed by a gradual cooldown beginning Tuesday
through the rest of the week, due to a breakdown in the ridge and an
increase in onshore flow. There will also be some monsoonal moisture
making its way over the area from Thursday through Saturday, as mid-
level flow becomes more southeasterly. This could allow for a could
of thunderstorms to develop over the mountains, especially in San
Diego County. The enhanced low level moisture will also help to cool
the deserts a tad, with highs back below 110F by Wednesday.

(Previous discussion submitted at 149 PM):

This weekend into Monday...

The upper level ridge fueling the heat wave that most are on the
other side of now has slid southwest compared to yesterday, allowing
for many locations to be about 5 cooler than yesterday. This
morning`s coastal eddy helped push a healthy marine layer inland and
with the strong subsidence inversion in place under the ridge,
these clouds have stuck around along most of the beaches/coast
this afternoon. With this, highs this afternoon should stay in the
low 70s along the coast, with upper 80s to mid 90s for the inland
areas, 70s to 80s for the mountains, and the deserts staying hot
- around 110-115 degrees.

The upper ridge becomes more centered just off the southern
California coast by Saturday before it broadens and strengthens some
for Sunday into Monday. With this setup, Saturday will be a touch
cooler than today, with Sunday/Monday warming back up to what we are
seeing today. The marine layer stays fairly consistent each
night/morning, with about 15 miles of inland extent and about 2000ft
deep.

Mid-late next week...

For Tuesday onward, a somewhat complicated pattern sets up where the
ridge splits and slides back eastward to the Four Corners while a
disturbance rounds the southern periphery of this ridge. This is a
highly volatile pattern and model guidance run to run consistency is
quite low. While the exact track of this disturbance is very
uncertain, what appears most likely in this setup will be a
gradual cooldown, bringing high temperatures back to near average.
Mid-level moisture would likely accompany any disturbance rounding
the south-southwestern periphery of the ridge, and if the timing
of some synoptic instability aligns, monsoonal thunderstorms may
be possible in the mountains sometime late next week. There is
only about a 5-10 percent chance of any precipitation and
uncertainty is very high, so stay tuned to see how this pattern
evolves as we get closer.

&&

.AVIATION...
110345Z....Coast/Valleys...BKN-OVC low clouds 1200-1500 ft MSL are
continuing to penetrate further into the inland areas this evening
and will extend to around 15 miles inland with high terrain obscured
in clouds/fog. Increasing chance for more clearing toward the coast
18-20Z Saturday with TAF sites clearing 17-19Z. Clouds will regather
tomorrow evening around 01-02Z and fill back in tomorrow evening,
with very little deviation in cloud base heights from where they are
this evening.

Mountains/Deserts...VFR conditions and unrestricted VIS through
this weekend.

&&

.MARINE...
No hazardous marine conditions expected through the middle of next
week.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.

&&

$$

UPDATE...Stewey
PUBLIC...Munyan
AVIATION/MARINE...Stewey