Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 221148
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
448 AM PDT Fri Mar 22 2024

.SYNOPSIS...
A little cooler today with coastal low clouds and fog this
morning. A low pressure system from the northwest will bring
greatest precipitation over the weekend from the coast to the
mountains with 6 inches or more of snowfall possible in the
mountains above 6000 feet. Gusty west winds will strengthen on
Saturday and continue into Sunday evening with the strongest winds
along the desert slopes of the mountains. Drier with warming for
Monday and Tuesday. A low pressure system from the northwest could
bring some light precipitation around Wednesday night. A more
substantial storm is possible toward the end of next week, but
with a lot of spread in the timing and details.

&&

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

.SHORT TERM (Today through Sunday)...
Satellite imagery early this morning shows low clouds over the
coastal waters only spreading slowly inland into coastal areas
with the marine layer shallower than 24 hours ago, around 1200 to
1400 feet deep. Fog could be locally dense near the mesas early
this morning. There are also high clouds spreading eastward
across the area. High temperatures today will be a few degrees
cooler than Thursday.

The cold front from a low pressure system near the West Coast will
move across southwestern California during the day on Saturday.
HREF shows rainfall and liquid equivalent above the snow level
through Saturday afternoon will range from one-tenth to one-
quarter inch near the coast to one-half to one inch in the
mountains.

Periods of showers will follow for Saturday night and Sunday, then
decreasing and ending from the northwest Sunday night. The upper
center of the low pressure system moves southeastward across the
area on Sunday afternoon with the greatest instability for Sunday
afternoon and early evening.

There will be periods of gusty west winds developing on Saturday
and continuing into Sunday, then decreasing late Sunday night. The
strongest winds are expected along and below the desert slopes of
the mountains with gusts to 60 to 70 mph. Gale force winds are
expected across the coast water with gusts of 35 to 40 mph at
times near the coast.

High temperatures on Saturday will be as much as 10 to 15 degrees
cooler than today for the mountains, inland valleys, and high
desert with the mountains and deserts another 5 degrees cooler on
Sunday for the mountains and deserts. With the cooling, high
temperatures for the mountains will be around 15 to 20 degrees
below average. Highs near the coast on Sunday will be near 60s and
mostly in the 50s for the valleys.

&&

.LONG TERM (Monday through Thursday)...
Monday and Tuesday will be warmer and drier with northwest flow
aloft. High temperatures on Tuesday will be around 5 degrees below
average for lower elevations to around 10 degrees below average
for the mountains.

A low pressure system from the northwest could move across the
area some time around Wednesday night and Thursday with a slight
chance for mostly light precipitation.

&&

.AVIATION...
220930Z...Coasts/Valleys...Low clouds will spread 10-15 miles inland
by 14Z. Bases will be around 500-900 ft MSL, briefly down to as low
as 300 FT between 11-15z, with tops to 1500 ft MSL. Areas of VIS 1-3
miles, locally below 1 mile where marine layer intersects with
terrain. 60-80 percent chance for CIG impacts at coastal TAF sites
through 17Z and up to 40 percent chance for CIG/VIS impacts at KONT
09Z-16Z. Expect clearing to the coast 17Z-19Z.

Mountains/Deserts: FEW-SCT clouds at/abv 20000 ft MSL with
unrestricted VIS through Friday.

&&

.MARINE...
No hazardous marine conditions are expected through Saturday
morning. Strong northwest winds will generate hazardous conditions
for Saturday afternoon through Monday. A Gale Watch has been issued
from Saturday afternoon through Monday morning. The strongest winds,
gusting 30-35 kts, and combined seas of 9-13 feet are expected late
Sunday.

&&

.BEACHES...
Large short-period swell from the west-northwest will arrive early
Sunday, peak Sunday night, and gradually subside Monday. This storm
swell will likely produce breaking waves up to 8-10 feet Sunday
night, highest in southern San Diego County.

&&

.HYDROLOGY...
Precipitation from a weakening cold front will move southward
across the area on Saturday. This will be followed by periods of
showers for Saturday night and Sunday with showers decreasing and
ending from the northwest Sunday night.

For Orange, southwestern San Bernardino, and western Riverside
Counties, rainfall is expected to range from one-quarter to one-
third inch near the coast to 1 to 1.5 inches in the mountains with
locally greater amounts. For San Diego County, rainfall is
expected to range from one-half to three-quarters of an inch near
the coast to 1 to 2 inches in the mountains with locally greater
amounts. There is also a slight chance of thunderstorms for late
Saturday night into Sunday evening.

ECMWF ensemble output continues to trend a little wetter for San
Diego with the ECMWF Extreme Forecast Index for rainfall now
having a small area of 90th to 95th percentile over southwestern
San Diego County for Saturday night and Sunday. For San Diego for
the weekend, around 75 percent of ECMWF ensemble members have
uncalibrated rainfall of 1 inch more.

A snow level of 6500 to 7000 feet for Saturday morning will fall
to around 4500 feet for early Sunday morning, then fluctuate
between 4500 and 5000 feet for Sunday afternoon and evening.
Snowfall of less than 3 inches is expected below 5000 feet, 3 to 6
inches from 5000 to 6000 feet, 6 to 12 inches from 6000 to 7500
feet, with locally 12 to 18 inches above 7500 feet.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory from 8 AM Saturday to 11 PM PDT Sunday 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 Watch from Saturday morning through Sunday evening
     for Riverside County Mountains-San Bernardino County
     Mountains.

PZ...Gale Watch from Saturday afternoon through late Sunday night 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/HYDROLOGY...17
AVIATION/MARINE/BEACHES...Adams


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