130
FXUS66 KSGX 181946
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
1246 PM PDT Fri Sep 18 2026

.SYNOPSIS...
Temperatures remain below normal into Wednesday with a present
marine layer. Warmer weather returns for the end of next week as
high pressure builds.

&&

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

Mid-level water vapor satellite imagery shows a trough over the
PacNW with a squished ridge just off the OR coast on the heels of
the trough. Temperatures warm Saturday as the trough is pushed
eastward and the ridge sets up over the West Coast, increasing
heights. Even with this pattern change, temperatures will still
remain below normal by about 1-4 degrees, with highs in the mid 70s
for the coast & mountains, 80s for inland spots and High Desert, and
near 100 for the lower deserts. The marine layer both Saturday and
Sunday morning will be slightly shallower than its been the past few
days, burning off quicker and not making it as far inland.

The ridge won`t remain in place for very long as a secondary trough
immediately behind it punts it eastward. This next trough is poised
to become a closed low, settling over Central CA by Monday. Onshore
flow will increase late Sunday and Monday while the marine layer
will deepen once again. Temperatures in turn will be cooler Sun-Tue,
coldest Monday, with highs 5-12 degrees below normal.

The pattern changes once again Wednesday as the trough becomes
absorbed into the upper level pattern with a massive low sitting off
the Canadian coastline. High pressure slides over the SoCal waters
and builds quickly late next week. This should return us to a
warming trend, rebounding temperatures back above normal. At this
point, models disagree on the overall placement of the high, as well
as how the aforementioned Canadian low might move. As such, models
show a significant temperature spread for the end of next week and
into the weekend, with some resolving highs closer to near normal
with others around 5-8 degrees above. Some guidance also indicates
that the southwesterly flow could push monsoonal moisture back up
into the SoCal mountains, but a clearer picture of where the high
pressure may be is needed before there is significant confidence in
this.

&&

.AVIATION...
181800Z...Coast/Valleys...Low clouds based 3000-4000 ft MSL are
swiftly retreating west, with clearing expected by 19-20z. SKC
through the afternoon, then clouds develop throughout lower SD
County 04-08z Sat at 2000-3000 ft MSL, before spreading into OC and
the south IE early Sat morning. Clouds are unlikely to make their
way into vcnty KONT/KSBD (only about a 15% chance for cigs). Clouds
clear offshore again 16-18z Sat.

Mountains/Deserts...Mostly clear and VFR conditions through Sat.

&&

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

&&

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

&&

$$

PUBLIC...Zuber
AVIATION/MARINE...CSP