Winter Storm Warning 1, NWS San Diego, CA

Area Forecast Discussion
National Weather Service San Diego CA
926 PM PST Tue Jan 30 2024

.SYNOPSIS...
A widespread cooling trend will start Wednesday, with below
average temperatures expected Thursday into early next week.
Windy, wet, and cloudy conditions are expected for the end of the
week. Widespread precipitation and gusty southerly winds are
expected Thursday with more scattered shower coverage and gusty
westerly winds Friday into Saturday. Additional rounds of
widespread precipitation expected sometime early next week.

&&

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

Evening update...
Scattered high clouds continue to drift over the region atop of a
weak short wave ridge off the coast. Surface pressure gradients
are trending onshore, and with that, a fog bank developed over the
coastal waters earlier this afternoon and briefly moved into the
coast. Dense fog may occur at the beaches and up to a few miles
inland tonight into Wednesday morning. Further inland, no
significant weather tonight. Widespread cooling is expected
Wednesday as a large Pacific trough begins to move towards the
coast, though highs inland will remain a few degrees above normal.

Previous discussion...
As a low pressure system moves inland through southwestern
California on Thursday, strong southerly winds are expected ahead of
the passing cold front. This will result in strong winds along the
coast, locally into the valleys. Southerly winds will rapidly weaken
after the trough passes becoming westerly and strengthening in the
mountains and deserts late Thursday. Gusty westerly winds will
continue over the mountains and into the deserts Friday and
Saturday. Peak wind gusts along the coast will be 40 to 50 mph, with
gusts 35 to 45 mph possible in the valleys. In the mountains and
deserts peak gusts of gusts 40 to 50 mph are possible.

Widespread moderate to heavy rain is also expected on Thursday.
There is also a slight chance of thunderstorms for Thursday into
Thursday evening over and west of the mountains. Rainfall totals
through Friday will range from 1.5 to 2 inches near the coast, 2 to
3 inches in the mountains, and 0.30 to 0.50 inch, locally closer to
0.75 inches in the deserts. Periods of heavy rain could generate
areas of in low-lying, flood-prone locations from the coast to the
deserts. After the widespread rain on Thursday, precipitation will
become more showery for Friday with light to locally moderate rain
expected. Areas of showers cannot be ruled out for Saturday although
Saturday is trending drier than Friday.

The current river forecast has the San Diego River at Fashion Valley
rising high enough to flood the low-water crossings by early
Thursday afternoon and rising above flood stage by early Thursday
evening. The Santa Margarita River is also forecast to reach monitor
stage by Thursday night, which could result in localized minor
flooding near the river.

The snow level will start at 6500 to 7000 feet Thursday morning at
the onset of the precipitation. Periods of heavy snowfall expected
in the San Bernardino and Riverside county mountains above 6500 feet
Thursday morning to early afternoon. Snow levels will fall to 4500
ft by early Friday. For Thursday through Friday evening snowfall
totals of 3 to 6 inches possible at 6000-7000 feet, 6-18 inches
possible at 7000-8000 feet, 18-24 inches possible at 8000 feet. 1-3
inches possible 4500-6000 feet on Friday. Precipitation coverage
will be scattered on Friday so widespread snowfall down to 4500 feet
looks unlikely at this time. A trace to a couple inches of snow are
possible 4000 feet and above in the San Diego County mountains on
Friday.

Additional widespread precipitation is expected sometime early next
week as another low pressure system off the West Coast directs
increased moisture into southwestern California. There remains a
wider spread in the details and potential impacts of the system
early next week.

&&

.AVIATION...
310450Z...Coastal areas...Patchy and intermittent low clouds and FG
this evening, becoming more widespread overnight. BKN-OVC with bases
200-500 FT MSL and vis 1-3 SM, below 1/4 mi in dense FG. FG
diminishes 16-18z Wed, though some beach locations may see
occasional cigs Wed afternoon, with rising bases to 700-1000 FT MSL.

Otherwise, FEW-SCT AOA 20,000 FT MSL through Wed night.

&&

.MARINE...
No hazardous marine conditions are expected through Wednesday.
Strong southerly winds develop Thursday morning, with peak gusts of
35 to 40 knots during the late morning hours. Winds turn to the
northwest and weaken slightly Thursday afternoon after a frontal
passage. Gales and hazardous seas are probable Thursday through
Friday. There is a slight chance of thunderstorms Thursday afternoon
and night.

&&

.BEACHES...
A large west swell with a period of 13-15 seconds will likely bring
high surf Thursday into Saturday, with surf reaching 6-10 feet.
Highest surf expected on exposed west-facing beaches of San Diego
County. There is also a slight chance for lightning Thursday
afternoon and night. High surf is possible again on Monday.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory from 2 AM Thursday to 6 AM PST Saturday for
     Orange County Coastal Areas-San Diego County Coastal Areas.

     High Wind Watch from late Wednesday night through Thursday
     afternoon for Orange County Coastal Areas-Orange County
     Inland Areas-San Bernardino and Riverside County Valleys-
     The Inland Empire-San Diego County Coastal Areas-San Diego
     County Valleys-Santa Ana Mountains and Foothills.

     Flood Watch from Thursday morning through Friday morning for
     Apple and Lucerne Valleys-Coachella Valley-Orange County
     Coastal Areas-Orange County Inland Areas-Riverside County
     Mountains-San Bernardino County Mountains-San Bernardino
     and Riverside County Valleys-The Inland Empire-San Diego
     County Coastal Areas-San Diego County Deserts-San Diego
     County Mountains-San Diego County Valleys-San Gorgonio Pass
     Near Banning-Santa Ana Mountains and Foothills.

     Winter Storm Watch from late Wednesday night through Friday
     afternoon for Riverside County Mountains-San Bernardino
     County Mountains.

PZ...Gale Watch from late Wednesday night through Thursday afternoon
     for Coastal Waters from San Mateo Point to the Mexican
     Border and out to 30 nm-Waters from San Mateo Point to the
     Mexican Border Extending 30 to 60 nm out including San
     Clemente Island.

&&

PUBLIC...SS/CO
AVIATION/MARINE/BEACHES...EA