-- Discussion containing changed information from previous version are highlighted. --
977
FXUS66 KSGX 240352
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
852 PM PDT Thu May 23 2024

.SYNOPSIS...
Cooling through Saturday with gusty southwest to west winds in the
mountains and deserts. The strongest gusts are more likely on
Friday afternoon into Friday night. Night and morning coastal low
clouds will extend inland across all of the valleys and onto the
lower coastal slopes of the mountains with slower daytime clearing
for coastal areas. High pressure to the south will bring warming
for Sunday through Wednesday. The marine layer will become
shallower with night and morning coastal low clouds only extending
inland into portions of the valleys by the middle of next week.

&&

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

.Evening Update...
Onshore flow continues at this hour, with some mountain passes
seeing wind gusts 40-60 MPH, mainly through the San Gorgonio Pass.
Winds will briefly drop off through the morning, before ramping
back up by Friday afternoon. As the trough progresses through the
area, winds will become more widespread into the deserts. There
is a low to moderate chance in seeing wind gusts over 45 MPH in
the deserts per latest HRRR and NBM model runs this evening.

Low clouds will continue to fill in the coastal basin through the
nighttime hours. HREF gives most areas a low chance in 50%+ sky
cover Friday afternoon, though with a deepening marine layer
throughout the day, clearing may be short lived near the coast.
Otherwise, minimal forecast changes through the cooler weekend and
warmer parts of next week.

.Previous Discussion (140 PM Thursday)...

A low/trough embedded in the mean cyclonic flow over the western
U.S. will move inland to our north tonight and Friday and will
bring stronger onshore flow. The marine layer will deepen, cooling
will spread inland, and there will be periods of gusty southwest
to west winds for the mountains and deserts with the strongest
winds for Friday afternoon into Friday night. The additional
deepening of the marine layer to 4500-5000 feet Friday night
into Saturday morning could bring patchy drizzle at lower
elevations west of the mtns.

There will be gusty southwest to west winds in the mountains and
deserts, with the stronger winds on Friday and Saturday. The winds
will peak Friday afternoon into Friday night with gusts mostly 40
to 50 mph except in the northern Coachella Valley below the San
Gorgonio Pass where winds could gust to around 60 mph.

High temperatures today will cool a few degrees from those on
Wednesday. There will be further cooling on Friday. The deserts
will continue to cool slightly on Saturday while the coast and
valleys warm slightly. With the cooling, high temperatures for the
mountains and inland valleys will be as much as 10 to 15 degrees
below seasonal averages on Friday.

For Sunday through Wednesday...
Building high pressure to the south will compete for dominance
with the low/trough to our north and could bring warming through
the middle of next week. The greatest warming is expected for
Sunday and Monday with slight additional warming for Tuesday and
Wednesday. With the warming, high temperatures on Wednesday will
be around average for the coast and valleys and around 5 degrees
above average for the deserts, mostly in the 80s for the Inland
Empire and the upper 90s to 104 for the lower deserts. The marine
layer will gradually decrease in depth with night and morning
coastal low clouds only extending inland into portions of the
valleys by the middle of next week.
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&&

.AVIATION...
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240400Z...Coast/Valleys/Foothills...BKN/OVC low clouds will continue
to spread overnight, reaching all areas by 11Z Fri with bases 1800-
2500 ft MSL and tops 2500-4000 ft MSL. Higher terrain will be
obscured but most VIS below the cloud bases will be 6+ miles. Slow
clearing will occur Fri with valley partially clearing 17Z-21Z Fri
with the coast partially clearing 18Z-22Z Fri, though bases will
generally rise to 2700-3700 ft MSL Fri in areas that remain cloudy
Fri afternoon. Stratus will become widespread again Fri evening.

Mountains/Deserts...Clear skies with mostly unrestricted VIS will
continue through Fri evening. Areas of winds from the west with
surface gusts 25-45 knots will occur at times through Fri evening
from the mountain crests east/north through the desert slopes and
into the deserts, including near San Gorgonio Pass. Strongest winds
will be after 00Z Sat. Local blowing dust could reduce VIS to 3-5
miles after 21Z Fri.
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&&

.MARINE...
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West to northwest winds will gust near or slightly over 20 knots in
the outer coastal waters (30-60 NM from the coast) each afternoon
and evening Friday through Sunday.
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&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory from noon Friday to 2 AM PDT Saturday for San
     Gorgonio Pass Near Banning.

PZ...None.

&&

$$

PUBLIC...APR/PG
AVIATION/MARINE...Maxwell