High Surf Advisory 3, NWS San Diego, CA

Area Forecast Discussion
National Weather Service San Diego CA
155 PM PST Mon Feb 13 2023

.SYNOPSIS...
Another low pressure system diving into the Great Basin later this
evening will bring strong west winds to much of the region along
with light precipitation generally from the mountains westward,
heaviest precipitation in the coastal mountain slopes. A brief
period of Santa Ana winds will follow on Wednesday, favoring some
warming and drying. Cold morning low temperatures can then be
anticipated Wednesday and Thursday morning. Another low pressure
system looks to arrive later this weekend, though details on
specific impacts remain uncertain at this time.

&&

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

The next wave in an active and amplified weather pattern will
dive into the Great Basin late tonight and Tuesday morning. The
primary impact from this system will be the strong westerly winds
blowing across the mountains and into the deserts, where High Wind
Warnings are now in effect starting this evening and lasting
through Tuesday evening. ECMWF EFI guidance suggests a majority of
ensemble members forecasting sustained winds and wind gusts
higher than the model climate, with SOT guidance favoring
significantly strong winds over portions of the mountains and
deserts. 700mb wind speeds, per the ECMWF model, ranging from
60-70kts will blow across the peninsular mountain ridgelines. This
is also supported by the CANSAC WRF depicting wind speeds
approaching 80mph in the desert foothills, raising concerns for
areas of blowing dust. SOT guidance also favors significant winds
over the coastal waters impacting the immediate coastline, where
Wind Advisories are also in effect from Tuesday afternoon through
Tuesday evening.

Precipitation impacts from this next system look to begin late
this evening and overnight, with most rain/snow tapering off late
Tuesday afternoon and evening. Snow levels generally start between
5500-6000 feet tonight, and then fall through Tuesday afternoon
when snow levels will range from around 4000 feet in the San Diego
County Mountains to as low as 2500 feet in the San Bernardino
County Mountains. Upsloping onshore flow will favor the coastal
mountain slopes for the heaviest precipitation, with localized
areas seeing precipitation totals of 0.30-0.60 inch occur. Areas
west of the mountains will receive less, generally under 0.25 inch
in most locations. Snowfall totals of 1 to 4 inches can be
expected for mountain communities above 4,000 feet in elevation.
With the combined impacts from snow and high wind, a Winter Storm
Warning has been issued from 06z Tue through 00z Wed for these
areas.

As this system departs to the east on Wednesday, colder and drier
air will filter into Southern California leading to cold morning
lows both Wednesday and Thursday morning. Wind-sheltered locations
will likely see frost develop, with potential for sub-freezing
lows in some isolated locations mainly in Riverside County between
the mountains and I-215. Winds will also shift to offshore flow
behind this system, favoring a brief round of Santa Anas on
Wednesday with the gustiest winds generally occurring below
mountain passes and through wind-prone canyons and valleys. This
also leads to a warming trend in daytime high temperatures,
warming a few degrees each day Wednesday through Friday. Despite
the warming trend, most locations will remain several degrees
cooler than seasonal normals through the weekend.

The next low pressure system approaches the California coast from
the northwest later this weekend. Differences in timing and track
of the 500mb low preclude any specific details regarding potential
precipitation and wind impacts. The general consensus track in EPS
guidance would favor similar impacts to last night’s storm which
favored the heaviest precipitation in San Diego County. The spread
in ensemble QPF guidance remains rather large, with EPS members
ranging from no precipitation at all to upwards of 1.2 inches in
24hrs starting on Saturday. Given the uncertainties, will keep
close to NBM guidance for this period.

&&

.AVIATION...
132130Z...SCT030-050 becoming OVC020-030 with tops to 060 after 02Z.
Areas of light rain 06Z-18Z Tuesday with occasionally lower CIGS 010-
020. Aft 18Z Tuesday...west winds increasing to 15-25kt at KSAN,
KCRQ and KSNA.

Mountains...SCT-BKN050 through 06Z. After 06Z...mtns becoming obscd
in clds and RA/SN through Tuesday evening with strong west winds 30-
40 kt gusting 70 kt.

Deserts...Mostly clear tonight. BKN030-050 Tuesday with -SHRA.
Strong northwest winds 20 to 30kt gusting 40 kt Tuesday afternoon
and evening.

&&

.MARINE...
A Gale Warning is in effect for both the Inner and Outer Waters
Tuesday and Tuesday night for WNW gales of 20-30 kt gusting 40-45
kt. Seas will build to 8 to 18 ft. The strong winds and short period
wind swell will make boating conditions extremely hazardous. The
strongest winds will surface Tuesday evening.

&&

.BEACHES...
A long-period northwest swell will generate elevated surf of 4 to 6
feet in San Diego County Tuesday and Wednesday.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory from 2 PM to 10 PM PST Tuesday for Orange County
     Coastal Areas-Orange County Inland Areas-San Diego County
     Coastal Areas.

     High Wind Warning from 10 PM this evening to 10 PM PST Tuesday
     for Apple and Lucerne Valleys-Coachella Valley-Riverside
     County Mountains-San Bernardino County Mountains-San Diego
     County Deserts-San Diego County Mountains-San Gorgonio Pass
     Near Banning.

     Winter Storm Warning from 10 PM this evening to 4 PM PST Tuesday
     for Riverside County Mountains-San Bernardino County
     Mountains-San Diego County Mountains.

PZ...Gale Warning from 1 PM Tuesday to 3 AM PST Wednesday for Coastal
     Waters from San Mateo Point to the Mexican Border and out
     to 30 nm.

     Gale Warning from 7 AM Tuesday to 3 AM PST Wednesday for Waters
     from San Mateo Point to the Mexican Border Extending 30 to
     60 nm out including San Clemente Island.

&&

PUBLIC...Adams
AVIATION/MARINE/BEACHES...Moede

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