Small Craft Advisory 9, NWS San Diego, CA

Area Forecast Discussion
National Weather Service San Diego CA
930 PM PST Tue Jan 24 2023

.SYNOPSIS...
Strong Santa Ana winds will develop late Wednesday and peak Thursday
with widespread windy conditions. Mild weather will prevail
Wednesday through Thursday, but a cooling trend will occur Friday
through the weekend as the Santa Ana winds weakens and the ridge of
high pressure diminishes. A trough of low pressure will likely bring
precipitation Sunday or Monday along with increasing west winds.

&&

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

Clear skies prevailed this evening with mostly light winds, except
for local easterly gusts over 20 MPH in the mountains and foothills.
Temperatures were considerably higher in the mountains versus 24
hours ago, with 5-12 deg F increases in many places. The valleys
were generally warmer as well, generally 3-5 deg F. With only 0.21"
of total precipitable water in the NKX sounding this afternoon,
there will not be much a "blanket" for the outgoing long-wave
radiation, so there should still be some frost in the valleys, but
fewer locations will be near or below freezing. It would be mainly
just the usual spots, like San Pasqual Valley, Ramona or around
Hemet. A warmer profile Wednesday should help a lot of lower
elevation locations reach around 70.

High pressure aloft prevails off the California coast with a long-
wave trough covering most of the CONUS. A short wave will move down
the west side of the long wave Wednesday and should be over western
Arizona by afternoon. We already have moderate MSLP gradients from
the Great Basin offshore to SoCal, but the surface pressure will
increase over the Great Basin further behind this short wave and
combine with mountain wave activity to bring strong Santa Ana winds.
While the flow aloft will be mostly northerly late Wednesday-
Thursday, the flow a little above the surface will be more easterly
(except more northerly near/below the Cajon Pass), which will mean
that San Diego County will experience substantially more wind than
with the event that occurred Monday morning. Overall, gusts around
or possibly over 75 MPH will likely occur in windy locations,
generally near and just west/southwest of the mountain crests. Some
gusts over 60 MPH could occur in some of the valleys, including
below the Cajon Pass, based on high-resolution model output. Model
output indicates more of the winds reaching the coast and coastal
waters than in most events, backed by strong MSLP gradients.

The winds should gradually weaken Friday, though some model guidance
still has strong MSLP gradients from the Great Basin to SoCal then.
OVerall, the East Pacific ridge will shift west, allowing for short-
waves moving south around the west side of the broad CONUS/Canadian
trough to have more impact on the West Coast. Most ensemble
solutions have precip sometime around Sunday through Monday night,
with the most likely scenario for precip being Monday. Cluster
analysis shows around 60-70% of the solutions following a pattern
that would give us generally 1/4 to 1/2 inch of rainfall near the
coast, with the rest of the solutions keeping SoCal mostly dry with
a weaker trough over our area. There should be snow in higher
elevations with snow levels likely 4000-5000 feet.

&&

.AVIATION...
250500Z...Local N-NE winds with sfc gusts 25-35 kt continuing along
the San Bernardino and Santa Ana coastal slopes/foothills and
locally into the Inland Empire through Wednesday morning. Areas of
moderate up/downdrafts and LLWS over/southwest of mtns.

Santa Ana winds will strenghten after 00Z Thursday (late Wednesday
afternoon) and spread across the coastal-valley areas after 04Z
Thursday, likely affecting KONT-KSNA-and KCRQ with low level wind
shear. Local N-NE winds with sfc gusts up to 60 kt will develop
Wednesday evening for much of the coastal slopes/foothills and
locally into the Inland Empire and Orange County through Thursday
morning with areas of strong up/downdrafts and LLWS over/southwest
of mtns.

Otherwise, conditions will remain mostly clear through Thursday
morning.

&&

.MARINE...
No hazardous marine weather conditions are expected through
Wednesday. Breezy northeast to east winds redevelop late Wednesday
night into Thursday morning, peaking Thursday morning with areas of
gusts possible up to 30 kt, mainly north of Pt Loma. Winds will
diminish Thursday evening into Friday but remain locally gusty near
the immediate coast in Northern San Diego County.

&&

.BEACHES...
A long-period west-northwest swell of 5-6 ft/17-19 sec from 290
degrees will bring elevated to locally high surf to the Orange and
San Diego County beaches into Wednesday. The surf will peak on
Wednesday, with local sets up to 8 ft in southern San Diego County.
Surf of up to 6 ft expected at remaining beaches. Swell and surf
will lower on Thursday. Strong rip currents possible at all beaches.

&&

.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 late Wednesday night for San
     Diego County Coastal Areas.

     High Wind Watch from Wednesday evening through Thursday evening
     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.

     Beach Hazards Statement through Wednesday afternoon for Orange
     County Coastal Areas.

PZ...None.

&&

PUBLIC...Maxwell
AVIATION/MARINE/BEACHES...JMB