768
FXUS66 KSGX 171038
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
238 AM PST Mon Nov 17 2025

.SYNOPSIS...
Isolated light showers will continue this morning along and west
of the mountains. A weaker Pacific storm will move through the
area this afternoon through Tuesday evening, bringing widespread
rain and mountain snowfall for areas above 5,000 feet. Isolated
showers continue into Wednesday with moisture wrapping around the
north side of the low pressure system. A third system may bring
additional by late Thursday or Friday, though details with this
system still remain uncertain.

&&

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

Isolated light showers continue to linger this morning as deep
layer moisture and onshore flow persist, otherwise high clouds are
moving across the region ahead of the next upper level low. This
low will track south along the coast today, slowly moving east
across So Cal Tuesday and Wednesday. The main band of
precipitation associated with the cold front moves through this
afternoon and evening, bringing another round of widespread
precipitation and a slight (10-15%) chance of thunderstorms with
it. Brief, heavy rain with rates upwards of 0.50"/hr are possible
within a narrow band right along the cold front. Isolated to
scattered showers will follow the front late tonight all the way
into early Wednesday. Ensembles are showing at least weak
instability (mean CAPE of around 100 J/kg) for the mountains
westward Tuesday afternoon, for another slight (10%) chance of
thunderstorms. Depending on how the low tracks and how slowly it
moves off to the east, we could remain in wrap around moisture on
the north and west sides of the low through the day Wednesday. If
it tracks slowly enough for moisture to remain into the afternoon,
we could see another round of showers as daytime
heating/destabilization occur, predominantly over the mountains
and deserts.

Storm total precipitation with this low are forecast to be around
0.50-0.75" for the coasts to the mountains, with amounts of 1-1.6"
on the south/southwest facing coastal slopes, 0.10-0.30" in the
deserts, and less than 0.10" in the deserts. Desert amounts could
end up being higher should the wrap around showers materializes.
Snow levels will be much lower with this system and have trended
lower since yesterday, now bottoming out at around 4500-5000 ft
across the San Bernardino Mountains and 5000-5500 ft in
Riverside/San Diego Counties Tuesday morning. This will be in the
colder air behind the front after the majority of the
precipitation occurs though, so do not expect much accumulation at
these elevations (less than 0.5" of snow). Snow levels will be
closer to 6500-7000 ft in the main precipitation band. Snow
totals for 5500-6500 ft will be near 1", 2-4" between 6500-7000
ft, and 4-8" above 7000 ft. Again, this amounts could end up
increasing if the wrap around showers occur, especially for the
northern slopes of the San Bernardino Mountains.

A brief break in precipitation occurs Wednesday night through
Thursday afternoon. Ensembles are starting to come into better
agreement with the track of the next system, though consequential
differences remain. They have trended away from the inside slider
track, which now only accounts for about 10% of the ensemble
space, meaning the potential for this storm to miss us with that
track has decreased. Around 20% of the members, the majority from
the GEFS, follow a track close to the deterministic GFS, swinging
the upper low further west and south before moving inland across
Northern Baja. The trajectory of the short waves around this low
will determine where the heavier precipitation occurs. A further
west and south track would favor San Diego County with lower
precipitation amounts to the north. A slight westward but less
southerly track would favor the coastal areas, and a more direct
route (much like the early week system) would more evenly
distribute precipitation across the region. The range of storm
total precipitation remains massive - anywhere from zero to over
an inch for the coasts to the mountains.

Once this upper level low departs (sometime Sunday or Monday),
weak upper level ridging will build in from the west bringing
drier weather and high temperatures returning to normal. Otherwise
highs will remain well below normal for the week, at times as much
as 15-20 degrees below normal.

&&

.AVIATION...
171030Z...SCT-BKN low clouds with cigs varying between 1800-4000
feet MSL along with iso -SHRA into this afternoon. A frontal band
arrives from the northwest starting in Orange County around 00Z and
into San Diego by 06Z, bringing RA, cigs 1000-2500 feet MSL, vis 1-
5SM, and a southerly to westerly wind shift. Higher terrain obscured
in FG/RA during this time and through tonight. Cigs/vis lifting
and/or scattering out near the coast after 07Z Tuesday.


&&

.MARINE...
A cold front will arrive late this afternoon with a distinct wind
shift from southerly to westerly. The strongest winds will be the
westerly winds behind the front this evening. Check the Small Craft
Advisory for details. There is a slight chance of thunderstorms this
afternoon and evening, and again Tuesday afternoon. Any thunderstorm
could produce lightning, gusty erratic winds, choppy seas, and/or a
waterspout. No hazardous marine conditions are expected Tuesday
night through Thursday, but the next storm system has the potential
to bring hazardous winds and seas Thursday night and Friday.

&&

.BEACHES...
Elevated surf of 3 to 5 feet, with sets to 6 feet on west facing
beaches is expected tonight and Tuesday. This will generate a high
risk of rip currents.

There is a slight chance of thunderstorms and lightning this
afternoon and evening, and again Tuesday afternoon.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 4 PM this afternoon to 2 AM PST
     Tuesday 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/BEACHES...MM