573
FXUS66 KSGX 210013
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
513 PM PDT Tue Oct 20 2026

.SYNOPSIS...
A low pressure system moving southward off the California coast will
bring general cooling through Thursday. It is also expected to
produce showers and a slight chance of thunderstorms for late
Wednesday through Thursday is it moves inland through California
into Nevada. Warmer and drier for next weekend. Offshore flow on
Saturday could produce gusty northeast to east winds in and below
mountain passes and canyons as well as the Inland Empire corridor
between the Cajon Pass and the Santa Ana Mountains. The offshore
flow weakens for Sunday into early next week.

&&

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

This afternoon...Skies are partly cloudy with only a few low
clouds off the coast, some mid and high clouds streaming in from
the southwest and cumulus clouds developing over the mountains.
Isolated showers over the mtns this afternoon can`t be ruled out
but the chances are very low. Temperatures are generally a few
degrees lower than at this time yesterday.

The low pressure system west of Point Conception continues to move
south today before turning east tomorrow. It will move through
SoCal on Thursday and Friday. It will bring further cooling, a
deepening marine layer with more low clouds, and widespread
precipitation. Showers could spread into coastal areas during the
afternoon on Wednesday. Those showers are expected to spread
farther inland for Wednesday night into Thursday with the greatest
chances for thunderstorms for late Wednesday night into Thursday.

Between Wednesday and Thursday night, rainfall across Orange and
southwestern San Bernardino Counties could range from around 1
inch near the coast to as much as 2 inches in the mountains. Rainfall
for San Diego County will range from around 1 inch in North County
to 0.50 to 0.75 near the border. High desert areas will receive
around 0.50 inch of rainfall and the low deserts will receive 0.25
inch or less. Probabilities for 0.10 inch or more of rainfall
from Wednesday morning through Thursday night exceed 90 percent
for the coast, valleys, and mountains. Probabilities for 0.50 inch
or more exceed 80 percent for the mountains as far south as the
northern half of San Diego County. Probabilities for 1 inch or
more range from 15 to 50 percent from the coast to the mountains
for Orange and southwestern San Bernardino Counties. Probabilities
for 2 inches or more exceed 10 percent for the mountains of
southwestern San Bernardino County.

High temperatures on Thursday will range from around 5 degrees
below average near the coast to 15 to 20 degrees below average for
mountain elevations above 6000 feet. High temperatures on Thursday
will be in the 60s to around 70 for the coast and valleys and in
the 40s and 50s for the mountains.

Precip tapers off late Thu into Fri as the low pressure system
moves eastward into AZ.

Warming and drying is expected for the weekend into early next
week, with some weak offshore winds possible Saturday and Sunday.
Offshore flow on Saturday could result in northeast to east winds
gusting 30 to 40 mph in and below mountain passes and canyons as
well as the Inland Empire corridor between the Cajon Pass and the
Santa Ana Mountains. The offshore flow weakens on Sunday.

For Saturday through Tuesday, high temperatures for coastal areas
will range from 5 to locally 10 degrees above average with inland
areas around 5 degrees below average to locally 10 degrees below
average in the mountains. High temperatures for the coast and
valleys will be mostly in the mid 70s to lower 80s with the lower
deserts in the lower to mid 80s with the mountains in the 50s and
60s.


&&

.AVIATION...
210000Z...Coast/Valleys...Low clouds based around 1800-2200 feet MSL
will develop over coastal areas and western valleys in the next few
hours. Low clouds fill into the southern Inland Empire after 06z Wed
and potentially fill into the northern Inland Empire overnight.
There`s a 30-40% chance for cig impacts vcnty KONT/KSBD. Vis reduced
3-6SM for elevated inland valleys. Low clouds scatter out relatively
early (13-16z) due to increasing upper cloud cover and decreasing
stability.

.Region-wide...SCT mid-level Cu over mtns and portions of
the coastal basin currently will slowly dissipate through this
evening. A band of -SHRA/SHRA will move through the region from west
to east Wednesday afternoon and evening. There is still some
uncertainty in exact timing, but impacts may start near KSNA/KONT as
early as 21z Wed and slowly progress eastward through the evening. A
few hours of 2000-3000 ft cigs and intermittent MVFR vis expected
for each TAF site in the coastal basin. A few embedded heavier
showers may produce local IFR conditions, mainly north of SD County.
Winds shift from south to southwest as the precip band passes
through.

&&

.MARINE...
A storm system will move through the coastal waters late Wednesday
through Thursday. Southerly winds Wednesday will shift to
southwesterly Wednesday night, then westerly Thursday, with
occasional wind gusts exceeding 20 knots. There is a 10-20% chance
of TSRA Wednesday night through Thursday. No additional hazardous
marine conditions are expected Thursday night through Sunday.

&&

.BEACHES...
Southerly swells will continue to bring surf of 3 to 5 feet with
sets to 6 feet, highest at south and southwest-facing beaches
through this evening (locally to 7 feet at Huntington Beach/The
Wedge). This will bring hazardous swimming conditions for most.
While surf and rip currents will be elevated, daily high tides will
not be particularly high, and the threat of coastal flooding is
minimal. See the Beach Hazards Statement for more details.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement until 11 PM PDT this evening for Orange
     County Coastal Areas-San Diego County Coastal Areas.

PZ...None.

&&

$$

PUBLIC...PG
AVIATION/MARINE/BEACHES...KW

NWS San Diego (SGX) Office