328
FXUS66 KSGX 131014
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
314 AM PDT Mon Oct 13 2025

.SYNOPSIS...
A low pressure system moving southward along the West Coast will
bring stronger onshore winds today into Tuesday night, along with
widespread precipitation from the coast to the mountains for tonight
into Tuesday night. Gradual warming and drying with periods of
weak offshore flow Wednesday through Friday. For next weekend the
warming continues inland while marine layer clouds and fog return
to the coastal areas.

&&

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

This morning...The marine layer is about 2000 ft deep, with a
strong coastal eddy helping to spread low clouds inland to the
coastal slopes of San Diego County and into the southern IE.

A low pressure system with a closed upper low over the OR coast
will move south along the coast into SoCal before turning inland
late Tue. It will then move east into NV/UT on Wed. This system
will bring cooler conditions, strong onshore winds, showers and a
slight chance for tstms as well as high elevation snow. The pool
of coldest air aloft remains north of the region so the chances
for tstms are small. Precipitation will begin tonight into early
Tuesday morning, starting in the northern and western areas
(vicinity LA basin) and spreading south and east through the day
on Tuesday before ending Tuesday night. Periods of heavy rainfall
are likely on Tue as the frontal band of showers moves through
the region. The heaviest rainfall will be mainly on the coastal
slopes of the San Bernardino Mtns, in the Santa Ana Mtns and
inland OC. Rainfall totals will decrease from north to south and
from west to east. Rainfall totals will range from 1+ inches in
the San Bernardino and Santa Ana Mtns to about a tenth of an inch
in the inland valleys of San Diego County near the Mexican border.
The high desert could receive around one half inch while the low
deserts will receive less than one tenths of an inch. The snow
levels will remain around 7000-8000 ft until most of the precip
has moved east so any snowfall accumulations will likely be above
those elevations. The mtn peaks in the San Bernardino Mtns could
get several inches of snow. The onshore winds have begun to
strengthen and the favored locations are currently reporting wind
gusts of up to 40 mph. The winds will peak tonight into Tue
morning with the wind-prone locations likely to see wind gusts of
55-60 mph. Tuesday will likely be the coldest day with daytime
high temperatures as much as 15-23 degrees below normal in the
inland valleys and mtns. The low deserts will be as much as 12-18
degrees below normal with temps in the 70s to near 80.

Fair weather will return for Wed through Friday with periods of
weak offshore winds as a sfc high follows the low pressure system
eastward into the Great Basin, setting up weak offshore pressure
gradients. Guidance indicates that this offshore flow may be
enough to keep marine layer low clouds from returning until the
weekend.

The warming trend continues next weekend as weak upper level high
pressure moves over the region. Any marine layer clouds that form
during the nights and mornings will mostly be restricted to the
coastal areas due to the shallowness of the marine layer.

&&

.AVIATION...
130930Z....Coasts/Valleys...Low clouds based near 1500-2000 feet MSL
and tops to 2500 feet will continue to fill most of the coastal
basin through 14Z. Scattering out will be somewhat haphazard and
temporary today between 18-00Z, but a little more likely inland.
Clouds will fill in after 00Z and head up mountain slopes, with
bases 2500-3500 feet MSL and some higher terrain obscured.
Increasing chances of -SHRA overnight, first in foothills, but
later anywhere mountains westward into Tuesday. Gusty W/SW winds
along desert facing slopes of the mountains into the deserts after
18Z continuing overnight into Tuesday. Wind gusts 25-40 kts
leading to MOD UDDFS and local LLWS in lee of mountains such as
vcnty KPSP. Local vis reduced 3-5SM in BLDU in deserts.

&&

.MARINE...
A robust eddy will strengthen today, with brisk winds gusting to
around 20 kts paralleling the coastline. Stronger southerly winds
will develop late tonight and peak Tuesday morning into early
afternoon and create conditions hazardous for small craft (check the
Small Craft Advisory for details). A front with a distinct wind
shift from southerly to westerly will move west to east across the
coastal waters Tuesday afternoon. Additionally, there is a slight
chance of thunderstorms Tuesday in the outer waters around San
Clemente Island northeast toward Catalina. Any thunderstorm could
produce briefly gusty, erratic winds, choppy seas, and lightning.

&&

.BEACHES...
There is a slight chance of thunderstorms and lightning Tuesday,
mainly in Orange County south to Camp Pendleton. Surf will also
increase for Tuesday, 3 to 5 feet, with occasional sets to 6 feet,
highest in San Diego County. This will produce a high rip current
risk.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Flash Flood Watch from late tonight through Tuesday afternoon
     for Orange County Inland Areas-San Bernardino County
     Mountains-Santa Ana Mountains and Foothills.

     Wind Advisory from 11 AM this morning to 11 PM PDT this evening
     for Apple and Lucerne Valleys-San Gorgonio Pass near
     Banning.

PZ...Small Craft Advisory from 2 AM to 5 PM PDT 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...PG
AVIATION/MARINE/BEACHES...MM