562
FXUS66 KSGX 192028
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
128 PM PDT Mon Oct 19 2026

.SYNOPSIS...
Onshore flow will begin to spread cooling inland today with a
return of coastal low clouds and fog likely for tonight into
Tuesday morning. A low pressure system from the north will bring
greater cooling for Wednesday and Thursday along with showers and
a chance of thunderstorms, most likely for Wednesday night through
Thursday afternoon. Then dry and warmer for next weekend.

&&

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

This afternoon...The inland areas, mountains and deserts are a
few degrees warmer than at this time yesterday while the coastal
areas are a few degrees cooler as onshore flow and a sea breeze
begin to spread marine air inland. Skies are clear except for a
few low clouds that formed over the coastal waters early this
morning.

Onshore flow ahead of a low pressure system approaching from the
northwest will help to spread the low clouds into the coastal
areas tonight. Initially, the clouds will be very low and there is
a chance of locally dense fog on elevated coastal terrain. A
developing coastal eddy, cyclonic flow aloft and falling heights
will cause the marine layer to deepen and the clouds to lift
overnight into Tuesday morning.

We can expect a general cooling trend through Thursday as the low
pressure system moves into SoCal. Thursday will likely be the
coolest day, with temperatures from a few degrees to as much a 15
degrees below normal. Ahead of the system, moisture from the low
latitudes will likely be drawn into socal with the flow aloft. The
system will use this moisture to produce light precipitation as
early as Wednesday morning. Precipitation will become more
widespread, progressing from northwest to southeast across the
region and increasing in intensity on Thursday as the system moves
through Socal. Conditions become most unstable on Thursday as
colder air moves in aloft from the northwest bringing a chance for
thunderstorms for Thursday morning through Thursday afternoon.
Precipitation will taper off by Friday morning as the upper level
trough axis moves east and conditions become more stable.

For Orange and southwestern San Bernardino Counties, rainfall
could range from around 1 inch for the Orange County coastal plain
to around 1.5 inches on the coastal slopes of the mountains
with amounts decreasing from north to south into San Diego
County. For the 24 hr period ending at 5 pm Thursday, there is a
35 to 65 percent chance of greater than 1 inch of rainfall in San
Diego County from the coast to the mountains. There is about a 30
to 45 percent chance of 1 inch or more in the Inland Empire and
about a 45 to 65 percent chance in Orange County, the Santa Ana
Mountains and on the slopes of the San Bernardino Mountains.

The snow level will drop to around 8,000 ft on Thursday afternoon
and the highest peaks of the San Bernardino and San Jacinto
mountains could get small amounts of snow.

The low pressure system will also bring periods of gusty southwest
to west winds in the mountains and deserts for Tuesday through
Thursday. Winds will likely be strongest on Thursday and gusts of
up to 40 mph could occur in the wind-prone locations.

Dry and warmer weather will return for the weekend under high
pressure aloft, with temperatures just below normal inland and
just above normal in the coastal areas.

&&

.AVIATION...
191700Z...Coast...VFR and SKC through late this evening. Low clouds
and fog much more likely to form after 05Z Tuesday, becoming more
widespread by 12Z Tuesday. Bases would be around 500-800 feet MSL
with vis 1-6SM on mesas and higher coastal terrain initially, with
bases and vis likely rising slightly Tue morning before clouds
scatter out 16-17Z.

Otherwise...Mostly clear and VFR conditions except for SCT-BKN
cumulus based around 10 kft over mountains 19-00Z.

&&

.MARINE...
No hazardous marine conditions are expected through Wednesday
morning. A storm system moves into the region later Wednesday
through Thursday, bringing gusts at or exceeding 20 knots and
associated choppy seas, along with a 10-15% chance of TSRA.

&&

.BEACHES...
Southerly swells will continue to bring surf of 3 to 6 feet with
local sets to 7 feet, highest at south and southwest-facing beaches
through Tuesday. 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. Further details can be found in the Beach Hazards Statement.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement through Tuesday evening for Orange
     County Coastal Areas-San Diego County Coastal Areas.

PZ...None.

&&

$$

PUBLIC...PG
AVIATION/MARINE/BEACHES...CSP

NWS San Diego (SGX) Office