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000
FXUS66 KSGX 221631
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
931 AM PDT Mon Apr 22 2024

.SYNOPSIS...
There will be a cooling trend through Thursday with stronger and
gusty southwest to west winds for the mountains and deserts for
Wednesday afternoon through Thursday night. The marine layer will
deepen with coastal low clouds extending inland into portions of
the valleys this morning and onto the lower coastal slopes of the
mountains by Thursday morning. There are small chances for drizzle
or light showers from this deeper marine layer, mainly for
Wednesday night into Thursday morning and again for Thursday night
into Friday morning. Then gradually warmer for Friday through
Monday with Sunday high temperatures around average and Monday
high temperatures around 5 degrees above average.

&&

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

Update...
The 12z Miramar sounding showed an 8C degree inversion based near
1450 feet, though a nearly saturated layer was noted as low as 450
feet. Extensive low cloud cover is present across the coast and
valleys, and no progress has been made in terms of clearing. The
valleys will slowly clear by late morning or early afternoon, but
the coast will likely remain under cloud cover much of the day.

A weakening ridge axis is moving eastward and a closed low will
progress southeastward through the eastern Pacific today. Cooling
spreads inland through the mountains today, with one last hot day
in the lower deserts. Highs will reach the mid to upper-60s at the
coast, the low to mid-70s across inland Orange/San Diego Counties,
the mid-70s to low-80s in the Inland Empire, the upper-60s to
mid-70s in the mountains, the upper-80s in the High Desert and the
upper-90s in the lower deserts. Further cooling will occur across
all areas tomorrow.

Previous Discussion (Issued 442 AM PDT Mon Apr 22 2024)...
.SHORT TERM (Today through Wednesday)...
High pressure aloft will begin to weaken today as a low pressure
system centered along 140 West longitude moves toward the
California coast, moving inland through southern California around
Wednesday night and Thursday.

High temperatures will begin to cool today with greater cooling on
Tuesday and additional lesser cooling on Wednesday. High
temperatures will go from as much as 5 to 10 degrees above
average today for the mountains and deserts to as much as 5 to 10
degrees below average for the valleys on Wednesday.

Onshore will strengthen for Wednesday and Thursday with gusty
southwest to west winds for the mountains and deserts for
Wednesday afternoon through Thursday night with the stronger gusts
on Wednesday night to around 50 to 60 mph.

The marine layer is expected to deepen from around 2500 feet this
morning to around 5500 feet on Thursday. There could be some
patchy drizzle or light showers from this deepening marine layer
with the greater chances for Wednesday night into Thursday morning
and again for Thursday night into Friday morning.

&&

.LONG TERM (Thursday through Sunday)...
The cooling will continue into Thursday with Thursday high
temperatures as much as 10 to 15 degrees below average for the
mountains and inland valleys. Slow warming will begin on Friday
with greater warming for Sunday and Monday with Sunday high
temperatures around average and Monday high temperatures around 5
degrees above average.

Cluster analysis shows the relatively greater chances for
precipitation on Friday, though light, is from the cluster that is
a little slower and more amplified with the low pressure system
near the California coast. This cluster is comprised mostly of
ensemble members of the ECMWF, but only around one-third of ECMWF
ensemble members are in this cluster.

&&

.AVIATION...
221620Z...Coast/Valleys...Low clouds with bases around 800-1000 feet
MSL and tops to 2000 feet will cover coastal areas and parts of
inland valleys. VIS 2-5SM along inland extent of clouds and over
higher coastal terrain. Inland clearing is expected 16-19Z but only
limited clearing at the coast, with SCT-BKN clouds persisting at
coastal TAF sites this afternoon. Low clouds to push ashore after
00Z and filling the entire coastal basin overnight into Tuesday.
Bases would be around 1000-1800 feet MSL, with vis restrictions
along inland edge of cloud and in higher valleys and foothills.

Mountains/Deserts...Mostly clear skies with unrestricted VIS today
and tonight.

&&

.MARINE...
No hazardous marine conditions are expected through Friday. Stronger
winds and possibly hazardous conditions Friday night.

&&

.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...EA/17
AVIATION/MARINE...Small