Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 211146
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
446 AM PDT Thu Mar 21 2024

.SYNOPSIS...
Cooling will begin to spread inland on Friday. A low pressure
system moving slowly inland along the West Coast for the weekend
will bring cooling and periods of strong and gusty west winds.
There will be widespread wetting precipitation from the coast to
the mountains with a chance of showers in the deserts. Then drier
with a warming trend for Monday through Wednesday.

&&

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

.SHORT TERM (Today through Saturday)...
The marine layer has deepened to around 2000 to 2500 feet with
satellite imagery showing coastal low clouds extending farther
inland into the San Diego County valleys and beginning to spread
into southern and western portions of the Inland Empire. High
temperatures today for most areas are expected to be within a few
degrees of those on Wednesday with Friday a few degrees cooler as
onshore flow begins to strengthen.

A low pressure system will move slowly inland along the West Coast
during the weekend. This will strengthen the onshore flow with
periods of strong gusty west winds, strongest for Saturday
afternoon into Sunday evening. The winds are expected to be
strongest along the desert slopes of the mountains with gusts to
60 to 70 mph. Strong winds across the coastal waters will extend
inland into coastal areas with gusts to near 40 mph. NBM has a
peak near the coast for late Saturday afternoon and again on
Sunday afternoon.

Timing hasn`t changed much with precipitation from the cold front
moving across the area during the day on Saturday. A snow level
near 6500 feet on Saturday morning will fall to around 4500 feet
for early Sunday morning.

&&

.LONG TERM (Sunday through Wednesday)...
There will be periods of showers for Saturday night into Sunday
evening with the greatest precipitation amounts and coverage
expected across San Diego County.

ECMWF ensemble output continues to trend wetter for San Diego. The
ECMWF Extreme Forecast Index for rainfall has an area of 70th to
80th percentile for Saturday night and Sunday for southwestern San
Diego County southward along the northern Baja coast. It was a
smaller area of 60th to 70th percentile for the forecast from 24
hours ago.

High temperatures will continue to cool on Sunday for the
mountains and deserts with the mountains 15 to 20 degrees below
average. Monday through Wednesday will be drier with a warming
trend with Wednesday high temperatures still a few to around 5
degrees below average.

&&

.AVIATION...
210930Z...Coasts/Valleys...Low clouds based at 1000-1500 feet MSL
will continue to infiltrate into some of the inland valleys through
sunrise. Tops will be around 1800 feet and vis 3-5SM in valleys and
higher coastal terrain. Scatter out expected 17-19Z. Low clouds will
push ashore and locally inland after 05Z Friday, although not as far
inland. Bases/vis should be slightly lower.

Mountains/Deserts: Mostly clear skies with unrestricted VIS today
and tonight, but with some cumulus buildups mainly over the
mountains at around 9000 feet MSL 20-01Z.

&&

.MARINE...
No hazardous marine conditions are expected through Saturday
morning. Strong winds will generate hazardous conditions for
Saturday afternoon through Monday. Strongest winds, including gales,
and highest seas are expected Sunday.

&&

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

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.

&&

$$

PUBLIC...17
AVIATION/MARINE/BEACHES...MM


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