590
FXUS66 KSGX 030419
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
919 PM PDT Sun Jun 2 2024

.SYNOPSIS...
A weak trough over the West Coast will keep a deep marine layer in
place through Monday. Pockets of drizzle are likely in some
coastal and valley areas late tonight through early Monday
morning. High pressure building over the Great Basin Tuesday
through Thursday will bring warmer weather to the valleys and
mountains, and hot weather to the deserts midweek. Cooler next
weekend with increasing onshore flow and a deeper marine layer.

&&

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

Evening update...
Satellite water vapor imagery shows an upper level low off the
coast of British Columbia with broad low amplitude troughing
across the West and widespread high clouds extending into So Cal.
Low clouds stuck to many portions of Orange and San Diego Counties
through the day and have already begun to spread back inland. The
00Z KNKX sounding shows the marine inversion based near 2600 ft
MSL, down substantially from around 3500 ft MSL this morning. A
coastal eddy is forecast to spin up again tonight which could help
the marine layer deepen. Either way it will be sufficiently deep
to extend into the inland valleys with some spotty drizzle
overnight.

Previous discussion...
From Tuesday through Thursday a 592 dm ridge builds over the eastern
Great Basin. This ridge position will bring hotter days to the
deserts where high desert highs Wednesday and Thursday will range
from 97-103. Heat Risk values in this area meet the criteria for an
Excessive Heat Watch which was issued today and will be in effect
Wednesday and Thursday. Affected communities include Victorville,
Hesperia, Apple Valley, Barstow and Yucca Valley.

The Lower Deserts will also be hotter midweek with highs from 105-
110 at Palm Springs, Coachella and Thermal. Mountain areas will be
warmer with highs from 80-90, as will the eastern portion of the
Inland Empire with highs from 90-95. Warming in the coastal areas
and the western valleys will be tempered by the marine layer and the
cooling onshore sea breeze. Highs will range from the upper 60s at
the coast to the upper 70s ten miles inland.

Latest guidance suggests a slower breakdown of the ridge high
pressure over the Great Basin later this week, and the desert heat
may persist into Friday before being forced east by a deepening
closed low over north-central Baja. This closed low, cut off from
the jet stream, will slowly meander north-northeast across northern
Baja Saturday, then cross into either Southern California or Arizona
Saturday night and Sunday. This trough may generate isolated
convection but that will depend on the instability and moisture
parameters, and the ultimate track of the low.


&&

.AVIATION...
030415Z...Coast/Valleys...BKN-OVC low clouds with bases 1500-2500 ft
MSL with tops to 3000 ft MSL will prevail in all coastal areas and
spread through most valleys by 09Z Mon. Higher terrain will be
obscured in clouds at times, with local VIS 2-4 miles in the valleys
08Z-17Z Mon. Clearing will occur Mon 16Z-20Z in the valleys and 18Z-
22Z near the coast, with areas of BKN clouds continuing near the
immediate coast through Mon afternoon. Low clouds will spread a
little less far inland Mon night.

Mountains/Deserts...Occasional SCT-BKN high clouds at/above 20000 ft
MSL will continue with unrestricted VIS through Mon evening.
West winds with gusts 25-40 kt will continue through 10Z Mon from
the mountain crests east through the desert slopes and into the
deserts, including through/near San Gorgonio Pass with MOD UDDFS.

&&

.MARINE...
No hazardous marine conditions are expected through Friday.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Watch from Wednesday morning through Thursday
     evening for Apple and Lucerne Valleys.

PZ...None.

&&

$$

PUBLIC...SS/Moede
AVIATION/MARINE...Maxwell