173
FXUS66 KSGX 040507
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
907 PM PST Mon Nov 3 2025

.SYNOPSIS...
A trough of low pressure will move closer to the West Coast
through Wednesday. This will bring a subtle cooling trend with
breezier conditions across the mountains and deserts by the middle
of the week. High pressure will regain strength by Friday into
the weekend, bringing warmer weather. The forecast becomes murkier
by the early to middle part of next week as interactions between
two pressure systems move closer to the region, one of which that
may bring cooler and potentially wetter weather.

&&

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

Evening update...

Marine layer clouds have been quite patchy and are struggling to
fill in across the coast and nearshore waters. These clouds will
eventually fill into a more cohesive deck of clouds, bringing
areas of fog for inland higher terrain and inland valleys
including portions of the Inland Empire.

From previous discussion...

Low clouds have faded away off the coast as high clouds begin to
thin over Southern California. A trough is beginning to
strengthen over the Northern Pacific. This system will continue to
move closer to the West Coast into the middle of the week. High
pressure to south will maintain its presence as well, keeping the
marine layer of similar depth by Tuesday, with a slight deepening
by Wednesday. This will garner more low clouds coverage to much of
the coastal basin each morning with elevated areas seeing foggy
conditions, like in the Inland Empire. Model guidance pushes the
area of low pressure to our north on Wednesday and Thursday. This
is when the coolest weather will occur over the week with highs
within 5 degrees of normal. The strongest part of the system will
move through on Wednesday, where the pressure gradient will
tighten to produce gusty west winds across the mountains and the
deserts. Model guidance indicates wind to be elevated with
widespread gusts 35-45 MPH, locally higher in the passes.

The area of high pressure to our south will begin to build in once
more by Friday into the weekend. This will lead to less wind and
warmer weather area wide. The ridge and associated surface high
will amplify over the Great Basin by Sunday. This will turn the
winds from the east, where weak Santa Ana winds will breeze
through the mountain passes and western valleys. NBM shows high
temperatures well into the 80s by the weekend across the western
valleys; would not be surprised if we see highs near 90 degrees in
these regions, including the Inland Empire and San Diego
foothills.

By Monday into the middle of the week, model ensemble guidance
begins to diverge on exactly what pressure systems will impact the
region. Models show a large trough forming off the Pacific this
weekend, but differences exist whether a part of the system will
impact our area or high pressure overhead this weekend will stick
around into early next week. Ensemble models show around 25% of
members becoming a bit wetter by next Tuesday or Wednesday. As of
now, confidence remains low on precipitation occurrence and
amounts for next week, but hints of pattern change are definitely
in our view as we head toward the middle of the month.

&&

.AVIATION...
040430Z...Coasts/Valleys...Areas of low clouds based 1000-1500 ft
MSL currently over coastal waters and coastal San Diego County.
Clouds will slowly expand in coverage and push 10-15 miles inland
through 09Z, then reach into the western Inland Empire (including
KONT) 09-12Z. Bases slowly lowering through 12Z to 500-1000 ft MSL
creating VIS reductions 2-5SM for elevated coastal terrain/western
valleys and locally 1/4-1SM for inland valleys/Inland Empire in FG.
4-6 SM down to sea level, including KSAN. VIS to improve 15-17z Tues
morning as bases rise. Scatter out 17-18z. Low clouds with slightly
higher bases return to coastal areas 00-03Z Tue, spreading into most
of the coastal basin overnight. Vis reductions for inland valleys
including the Inland Empire.

Mountains/Deserts...VFR conditions expected through Tuesday evening.

&&

.MARINE...
Long period west to northwest swell will move into the coastal
waters starting on Thursday. Swell height 4-5 feet and periods 14-16
seconds should produce elevated surf along west-facing beaches, with
wave heights peaking on Friday and slowly coming down through the
weekend.

&&

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

&&

$$

PUBLIC...Munyan
AVIATION/MARINE...KW