508
FXUS66 KSGX 221706
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
906 AM PST Sat Nov 22 2025

.SYNOPSIS...
Widespread precipitation across the lower deserts and adjacent
mountain slopes through this morning with showers occasionally
making it west of the mountains. Snow levels will rise from 6500
to 7000 ft today. Showers tapering off this afternoon into tonight,
with dry conditions expected to return by Sunday. Periods of
gusty northeast to east winds will continue through this evening.
A gradual warming is expected for next week, with high
temperatures returning to above normal by the middle of the week.
A weak Santa Ana is possible sometime mid-week.

&&

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

Current radar as of 830 AM shows widespread light precipitation
east of the Peninsular range. Some light rain has made it over the
mountains, drifting westward through the Inland Empire and
through the San Diego County valleys toward the coast.

Orographically forced snow showers continue for the eastern slopes
of the San Bernardino and Riverside County mountains above 7,000
feet. Breezy snow showers along with patchy fog above 5,000 feet
are causing reduced visibilities for many east facing mountain
areas. High resolution guidance continues to show most of the rain
and snow shower activity wrapping up and moving eastward by noon
with only a slight chance for any given area to experience a stray
shower through the afternoon hours.

Northeast and east winds continue to gusts to 35-50 mph along west
facing foothills and mountain slopes, expecting to weaken around
4PM.

Otherwise, drier and calmer weather expected for Sunday.

Previous discussion issued 230 AM November 22...

The upper level low is currently centered off the coast of
northern Baja and will begin its eastward progression as a vort
max rounds the base of the low. Another vort max is lifting north
on the eastern side of the low, and as a result widespread light
precipitation has developed over the deserts with a few light
showers also wrapping around from the north. Light showers will
occasionally drift west of the mountains today, but for the most
part the bulk of the precipitation is forecast to occur over the
deserts and adjacent mountain slopes. Rainfall accumulations in
these areas will range from around 0.10-0.40 inch, with isolated
amounts closer to 0.80 inch on the east slopes of the Laguna
Mountains. West of the mountains any additional accumulation will
be less than 0.10 inch. Snow levels are still hovering around 6500
ft, but will rise to 7000 ft later this morning. Additional snow
accumulations of a few tenths to around 2 inches is expected,
locally higher on the east side Onyx Peak and Mt San Gorgonio.

Showers will gradually taper off this afternoon into tonight as
the low moves eastward, ending by early Sunday morning. Northeast
to east flow around the north side of the low and offshore
pressure gradients will cause breezy winds to continue across the
coastal mountain slopes and below the passes with local gusts up
to 45 mph in the wind prone areas this morning. Winds weaken this
afternoon as gradients and mid-level flow weaken.

Once the low moves out, an upper level ridge will move in from the
west and amplify into midweek, bringing a warming trend. Surface
high pressure building in over the Great Basin behind a pair of
weak short waves will drive a round of true Santa Ana winds
Tuesday through Thanksgiving, causing additional warming west of
the mountains where high temperatures will be around 5 to 10
degrees above normal on Thanksgiving. CW3E West-WRF now has a 40%
chance of weak to moderate Santa Ana Winds on Tuesday and
Thursday, and a peak of around 55% on Wednesday. There is a 15%
chance of a moderate event on Wednesday. Given the lack of any
upper level support, winds will generally be confined to the usual
passes/canyons and coastal slopes.


Beyond Thursday, ensembles are struggling with the breakdown of
the ridge and an upper level trough approaching. In general,
Friday should be cooler with a return of onshore flow. The timing
and track of the next upper trough is still all over the place,
some showing a lower amplitude trough, potentially as an inside
slider which would lower precip chances here, others digging the
low further south with a slower track which would result in higher
precipitation chances/amounts but delayed a day or so. For now
forecast follows NBM PoPs which brings a slight chance in
beginning Saturday morning, increasing to around a 20-30% chance
Saturday night.

&&

.AVIATION...
221630Z...Coasts/Valleys...Currently, patchy -RA occurring in valleys
and and areas eastward, favoring eastern facing mountain slopes and
adjacent deserts. FEW-SCT bases 5-7 kft MSL and an OVC layer based 8-
10 kft MSL. FG to reduce vis 0-2 SM above 5000 ft MSL and SNSH to
reduce vis 0-5SM above 7000 ft, especially along east facing slopes.
-RA/SNSH taper off after 20z along with vis improvements in the
mountains. In the afternoon, only a slight (20%) chance for a
leftover ISO SHRA/SNSH for any given area. East to northeast winds
gusting 25-35 knots in the coastal foothills and locally into
valleys through about 00z Sunday.

&&

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

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Winter Storm Warning until 10 AM PST this morning for Riverside
     County Mountains-San Bernardino County Mountains.

PZ...None.

&&

$$

PUBLIC...Westerink
AVIATION/MARINE...Westerink

NWS San Diego (SGX) Office