226
FXUS66 KSGX 200521
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
921 PM PST Wed Nov 19 2025

.SYNOPSIS...
Cool and dry tonight then isolated light showers developing west
of the mountains Thursday morning. The next low pressure system
from the northwest will bring more widespread showers late
Thursday afternoon into Friday. With snow levels lowering to
around 6000 feet late Thursday night, there could be moderate to
heavy snowfall in the mountains above 6500 feet. Some showers
could linger into Saturday. Drier and warmer next week with high
temperatures warming to within a few degrees of average for
Tuesday and Wednesday.

&&

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

Evening update...
Water vapor imagery shows the center of the upper level low has
finally moved east into Arizona with drier air in place over So
Cal. As a result, showers have finally come to an end with some
clouds lingering across the foothills. With enough clearing
tonight, pockets of shallow fog could develop in the valleys.
Otherwise cool with lows in the 40s in the valleys and low
deserts, mid to upper 30s in the high desert, and low 20s to mid
30s in the mountains.

The next upper level trough is off the Pac NW coast and digs south
on Thursday with a closed low developing in base of the trough.
Isolated light showers are forecast to develop ahead of this
system Thursday morning as moisture and onshore flow increase. Any
accumulation with these morning showers will be limited to a few
hundredths of an inch.

From previous discussion...
The upper level closed low, similar to the last system, will
situate right off the coast of Southern California Thursday/Friday
before moving inland Saturday. There will be less moisture with
this upcoming low compared to the system this past weekend, but we
are still looking at widespread rainfall for the end of the week.
Showers will begin as early as Thursday morning, becoming
widespread and heavier Thursday night and Friday morning, with an
associated thunderstorm threat during this time period. Rain may
continue for much of the day Friday as the low moves into
the CA bight, with increasing winds over the marine waters and
the higher elevations. This system looks to only produce moderate
winds with limited gradient tightening and relatively weak mid-
level flow. Still, gusts in the deserts, mountains, and coastal waters
could reach up to 30 mph at times on Friday. The thunderstorm
threat lessens Friday afternoon, with only light to moderate rain
showers prevailing into Saturday.

The snow level for the beginning of this event looks to hover
right around 6000 ft, raising a bit to 6500 ft Thursday night
into early Friday morning coinciding with the timing of the
heaviest precipitation. With snow levels rising, elevations
between 5500-6500 ft will see a mixture of snow/rain,
transitioning to more rain by Friday morning. Periods of rain with
rates greater 0.50"/hr will fall on already highly saturated
soils, which may cause an increased threat of runoff and minor
flows on and around recent burn scars. Always monitor the forecast
and listen to local emergency officials. Above the snow level,
snowfall rates could reach 1"+/hr, primarily in the early Friday
morning time frame. Snowfall totals Thursday through Saturday of
2-6 inches for elevations above 6500 ft and around 6-12 inches
above 7000 ft, with up to 16 inches for the highest peaks. A
Winter Storm Watch is in effect for elevations above 6500 ft for
this period, and heavy snow in the early morning hours of Friday
may make travel hazardous. Avoid travel during this time if
possible, especially along Hwy 38 near Big Bear. If you must
travel, ensure you have emergency supplies in your car and have a
way to contact emergency services in low cell coverage areas.

This system will follow a similar path to the closed low exiting
today, moving into Arizona Saturday into early Sunday. As this
system moves across, wrap around moisture will result in lingering
light rain and snow showers across the region, best chances in
San Diego and Riverside counties. High uncertainty remains on
timing and accumulations Saturday due to the model spread in the
movement of the low, fairly unusual to have such limited agreement
72 hours out. Snow levels will remain around 6500 ft on Saturday,
rising closer to 7000 ft by early Sunday. As the last of the
precipitation moves out, a slow warming and drying trend will
settle in for the remainder of the forecast period. Highs may
return to near normal by Tuesday/Wednesday as weak ridging
develops overhead, and dry weather prevails after Sunday.

&&

.AVIATION...
200430Z...FEW clouds remain region-wise, mainly between 2-7 kft MSL.
Increasing clouds around 2500-4000 feet MSL throughout the coastal
basin after 08Z Thu with ISO -SHRA 09-12Z for San Diego/Orange
County coasts and valleys ahead of the next storm system.

CIGS mostly remain above 3 kft through 23z, then lower to 2-3 kft
ahead of the frontal passage along with SCT -SHRA and a surge of
southerly winds. The frontal passage arrives in northern Orange
County around 01z, sweeping through the region from northwest to
southeast, reaching KCRQ and KSAN around 04z Fri. Expect 3-5 hours
of RA/+RA and briefly strong south, then west winds gusting to 20-25
kts during frontal passage. VIS locally 0-3SM and bases briefly
below 1000 ft MSL during heaviest periods of rain, though generally
4-6SM with bases 2-4 kft MSL in -RA/RA.

Mountains shrouded in FG; snow showers above 6,500 feet after 23z,
reducing VIS 0-5SM.

&&

.MARINE...
Southerly winds will increase late Thursday ahead of the next storm
system. Moderate confidence in winds turning westerly and
strengthening by early Friday as the front passes, but exact track
of the low pressure system may create large differences in both wind
speed and direction Thursday evening through Friday. Gusty winds and
choppy seas may create hazardous conditions for small craft. See
Small Craft Advisory for details. There is also a slight chance of
thunderstorms late Thursday through late Friday. Any thunderstorm
could bring lightning, gusty winds, choppy seas, and a waterspout.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Winter Storm Watch from Thursday morning through Saturday
     morning for Riverside County Mountains-San Bernardino
     County Mountains.

PZ...Small Craft Advisory from 4 PM Thursday to 1 AM PST Saturday for
     Coastal Waters from San Mateo Point to the Mexican Border
     and out to 10 nm-Waters from San Mateo Point to the Mexican
     Border Extending 10 to 60 nm out including San Clemente
     Island.


&&

$$

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