Winter Storm Warning 3, NWS San Diego, CA

Area Forecast Discussion
National Weather Service San Diego CA
901 AM PST Fri Mar 1 2024

.SYNOPSIS...
This weekend, a large low pressure system over the northeast
Pacific will move slowly inland along the West Coast. Gusty west
winds for the mountains and deserts will strengthen into the
weekend. Winds are expected to be strongest Saturday afternoon and
night with gusts to 70 to 80 mph and isolated gusts to 90 mph
with the strongest winds over the mountain ridges onto the desert
mountain slopes. Precipitation is expected from the coast to the
mountains for for late today into Sunday with the greatest chances
on Saturday. The snow level will fall from around 6000 to 6500
feet on Saturday to 5000 feet on Sunday. It will be drier and a
little warmer for Monday into Tuesday with the next chance for
precipitation around the middle of next week.

&&

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

Update...
At 9 AM, scattered mid-level clouds are seen from the coast
through the mountains. A very intense 509 DM storm system is
churning off the coast of British Columbia today and longwave
troughing is covering Southern California. Onshore winds will be
on the increase this afternoon across the mountains and deserts,
increasing further on Saturday. Rain chances will begin to
increase across northern areas this evening, spreading farther
south and east by Saturday morning. Hi-resolution guidance this
morning is trending slightly heavier across the San Bernardino
County Mountains on Saturday, so adjustments may be made to
increase rain amounts with the afternoon forecast package.

Previous Discussion (Issued 426 AM PST Fri Mar 1 2024)...
.SHORT TERM (Today through Sunday)...
The marine layer has continued to deepen with patchy drizzle from
the coast to the coastal slopes of the mountains. Measurable
amounts have been spotty so far with the greatest amounts, to
around 0.05 inch, on the coastal slopes of the San Bernardino
Mountains.

A large cold low pressure system off the coast of British
Columbia and the Pacific Northwest will move slowly inland through
the weekend. This will continue to strengthen the onshore flow
across southern California into the weekend. The strongest winds
are expected for the mountains and deserts on Saturday afternoon
and night. Southwest to west winds are expected to gust to 70 to
80 mph on the desert slopes of the mountains with isolated gusts
to 90 mph.

The cooling trend will continue into Saturday with high
temperatures for mountains and inland valleys 10 to 15 degrees
below average. There will be slight warming on Sunday.

Through Sunday for Orange and southwestern San Bernardino
Counties, rainfall is expected to range from around one-third
inch near the coast to 1 to 2 inches the mountains with isolated
amounts to around 3 inches on the coastal slopes.

For San Diego and western Riverside Counties, rainfall is expected
to range near the coast from one-third inch for northern San
Diego County to around one-tenth inch for southern San Diego
County to one-half to one inch in the mountains.

A snow level around 6000 to 6500 feet on Saturday is expected to
fall to around 5000 feet on Sunday with snowfall of 3 to 6 inches
in the mountains above 6500 feet with isolated greater amounts
above 7500 feet. Around 1 to 2 inches is possible between
6000-6500 feet.

&&

.LONG TERM (Monday through Thursday)...
There will be drying and warming for Monday and Tuesday, but with
high temperatures on Tuesday still around 5 degrees below average
for inland areas. The next chance for precipitation will be around
the middle of next week with larger model spread in the details.

&&

.AVIATION...
011700Z...Coast/Valleys...SCT-BKN030-050 for most of the TAF period.
Areas of RA expected as early as 10Z Sat for Orange County and the
Inland Empire. RA will move south into San Diego County 13-15Z Sat.
Periods of SHRA expected through at least 00Z Sun. Cigs will be 2000-
3500 ft MSL, locally down to 1000 ft MSL in heavier showers. Areas
of vis down to 2-4 SM in SHRA. Along the coast southerly winds from
180-200 degrees could gust to 20 kt, most likely 12-16Z Sat.

Mountains/Deserts...West and southwest facing mountain slopes obscd
in clouds and fog at times today, becoming more widespread after 06Z
Sat. Mostly clear in the deserts today with increasing mid to high
clouds Sat. Areas of SHRA/SHSN increasing after 06Z Sat.

SW-W wind gusts 25-35 kt on the desert mountain slopes and into the
deserts with MOD UDDFS/LLWS today. Increasing winds 06Z-20Z Sat,
with gusts 40 to 65 kt on the desert slopes of the mountains. After
20Z winds increasing to 50-70 kt. In the deserts, peak gusts will be
30-40 kt 06-20Z Sat, with gusts to 55 kt after 20Z. Strong LLWS and
severe turbulence expected over the mountains and into the deserts.
Strong winds are expected to continue into Sunday morning.

&&

.MARINE...
Friday night through Sunday: Scattered showers and westerly winds
gusting 20-25 kt at times. Winds shifting northwest Sunday night and
Monday. Choppy seas from a short-period wind swell.

&&

.BEACHES...
A long-period northwest swell of about 4 feet, followed by a short-
period northwest of about 5-7 feet will bring surf of 4-7 feet
Saturday night through Monday. The highest surf will be on exposed
west-facing beaches in San Diego County.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...High Wind Warning from 6 PM this evening to noon PST Sunday for
     Apple and Lucerne Valleys-San Bernardino County Mountains-
     San Gorgonio Pass Near Banning.

     Winter Weather Advisory from 10 PM this evening to 6 AM PST
     Sunday for San Bernardino County Mountains.

     High Wind Warning from 6 AM Saturday to noon PST Sunday for
     Riverside County Mountains-San Diego County Mountains.

     Winter Weather Advisory from 6 AM Saturday to 6 AM PST Sunday
     for Riverside County Mountains.

     Wind Advisory from noon Saturday to midnight PST Saturday night
     for Coachella Valley-San Diego County Deserts.

PZ...None.

&&

PUBLIC...EA/17
AVIATION/MARINE...CO