231
FXUS66 KSGX 132100
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
200 PM PDT Mon Oct 13 2025

.SYNOPSIS...
A low pressure system moving southward along the West Coast is
bringing stronger onshore winds to the area which will last
through Tuesday night. Widespread precipitation from the coast to
the mountains for tonight into Tuesday night. Moderate to heavy
rainfall rates will present a moderate flood risk, especially for
northwestern valleys and coastal slopes. Gradual warming and
drying with periods of weak offshore flow Wednesday through
Friday. For this 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...

An incoming low pressure system will contribute to strengthening
onshore flow across Southern California today. This will reinforce
the marine layer and allow for low clouds coverage to remain
broken throughout the day across the coastal basin. Otherwise, a
cool and breezy day with temperatures 5 to 15 degrees below
average.

As the upper low slides down the West Coast this afternoon, winds
will become elevated to strong for the mountains and deserts.
Widespread wind gusts 30-45 mph from early this afternoon through
late tonight. Gusts may exceed 60 mph along wind-prone mountain
passes and canyons. Winds weaken slightly for the mountains and
deserts by Tuesday morning, but should remain elevated throughout
the day as the storm system passes. This system will also bring
cooler temperatures, widespread rain and mountain snow above
7000-8000 ft. Precipitation will begin as orographic light rain
along coastal slopes this afternoon before widespread light to
moderate showers push into western areas late this evening.

The main frontal band will move across the area from northwest to
southeast throughout the day on Tuesday. Widespread moderate
rainfall rates expected from the coast to the mountains. Areas of
heavy rainfall are likely, especially for Orange County, western
Inland Empire and coastal slopes of the San Bernardino County
Mountains where rates 0.4-0.8"/hr are expected. Isolated
thunderstorms possible in these areas. Rainfall totals will range
from over 2 inches along the western coastal slopes of the San
Bernardino County Mtns to less than a tenth of an inch for most of
the lower deserts. Widespread 0.5-1" for lower elevations from
northern San Diego County and areas north. Higher amounts in
surrounding mountains. A quarter to half an inch expected in the
San Diego metro area with localized higher amounts. A similar
story for the High Deserts. Accumulating mountain snow above 7000
feet with several inches expected along the highest peaks. A
dusting of snow may occur down to Big Bear Lake. Chance for a few
post-frontal convective showers in the evening and overnight
Tuesday from the coast to the mountains, but these would be light
and intermittent should they occur.

Quiet weather returns along with gradual warming from Wednesday
onward as the trough exits the region and is slowly replaced by
weak upper level ridging by the weekend. Surface high pressure
will be in place over the intermountain west in the wake of the
storm system, allowing for weak offshore pressure gradients. This
may prevent marine layer clouds from reforming for a couple of
days.

The warming trend continues this 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...
132100Z...Low clouds continue to spin over the coastal basin this
afternoon with BKN bases near near 4000-5000 feet MSL. High
confidence SD County and Inland Empire regions staying mainly BKN
this afternoon with partial clearing seen across OC. Any scattering
that does take place will be replaced with BKN-OVC cigs after 00Z.
Bases lowering after this time near 2500-3500 feet MSL and some
higher terrain obscured. Increasing chances of -SHRA after 02Z,
first in foothills, but later anywhere mountains westward into the
evening. S/SW winds continuing to gust over 20 kts at times through
the night at coastal TAF sites.

A Pacific storm system will bring areas of +RA/ISO TSRA 10-18Z near
the LA Basin, SBD mts. -RA by 14Z-21Z in San Diego County. Areas of
3-5SM vis in +RA/ISO TSRA. As heaviest rain moves through, S/SW
winds increasing with moderate confidence in wind gusts reaching 30
kts at all coastal TAF sites for a short period. Winds weakening on
Tuesday afternoon from northern areas to southern areas.

Mtn Desert Slopes/Deserts....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. Winds slightly weaker and more
confined to desert slopes on Tuesday.

&&

.MARINE...
A robust eddy continues to bring 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
morning and early afternoon, 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 until 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...KW
AVIATION/MARINE...APR