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458
FXUS66 KSGX 041627
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
927 AM PDT Sat May 4 2024

.SYNOPSIS...
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Cloudy and cool conditions expected this weekend with periods of
gusty winds in the mountains and deserts and periods of showers in
and west of the mountains. Strongest winds and most likely time of
precipitation is tonight into early Sunday morning. Winds will
weaken slightly during the day Sunday but remain elevated into
Sunday evening. Dry conditions are expected by Sunday afternoon. Dry
and gradually warming conditions expected for much of next week.
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&&

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

The marine layer is about 2000 ft deeper than it was 24-hours ago.
Low clouds have filled in the entire coastal basin and mountain
passes. A few areas of drizzle are still being reported as of 9 AM.
Areas of clouds are expected to stick around for much of the day,
but periods of sunshine are possible today especially for inland
areas. High clouds will become more widespread through the day ahead
of a low pressure system that will move inland across northern
California. This low will dig into the Great Basin into Sunday,
bringing cold and windy conditions with periods of showers to
Southern California. High temperatures today will be around 3-7
degrees below normal for most areas, near normal in the low deserts.

Gusty southwest to west winds are expected over the mountains,
through passes, and into portions of the deserts. Winds will slowly
increase in strength through this afternoon and evening, peaking
late tonight into early Sunday morning. Winds will weaken slightly
through the day Sunday but remain elevated into Sunday night. Peak
wind gusts will be 50 to 60 mph with isolated gusts to 70 mph
possible through the San Gorgonio Pass. The windiest locations will
be on the desert slopes of the mountains and through/below passes
into the deserts. Another round of weaker but still gusty west winds
will occur Monday afternoon and evening.

The trough axis of the low and associated cold front are expected to
quickly pass through Southern California tonight into early Sunday.
Periods of mostly light rainfall are expected for areas in and west
of the mountains as the front passes. As far as rainfall totals go
generally less than 0.15 inch expected for the coasts/valleys with
local amounts around 0.25 inch near the foothills. Orographics will
enhance precipitation along the coastal slopes of the mountains with
amounts of 0.25-0.50 inch, upwards of 0.75 inch on the southwest
facing slopes of the San Bernardino Mountains. Amounts in the High
Desert, if any, will be a couple hundredths of an inch, with no
precipitation expected in the low deserts. Precipitation will come
to an end by early Sunday afternoon. Snow levels will begin near
7500-8000 ft tonight, falling to around 5500 ft behind the cold
front as precipitation tapers off. Any snow accumulation will be
limited to an inch or less.

High temperatures on Sunday will be 15-20 degrees below normal for
inland areas and 5-10 degrees below normal near the coast. Cool
conditions expected Monday morning before temperatures rebound
during the day. Low temperatures Monday morning will be quite chilly,
especially for the High Desert and mountains with lows in the mid to
upper 30s for the High Desert and mid-20s to mid-30s for the
mountains. Conditions are expected to gradually warm Tuesday into
much of next week, although there is some uncertainty in the
forecast for the middle to end of the week. By Wednesday, ensembles
are pretty much split half and half on warmer vs cooler scenarios.
By Thursday, the cooler scenario with the low retrograding much
further SW is the outlier containing only 7 percent of global
ensemble members. Given the large uncertainty the current forecast
follows NBM for temperatures which shows a very subtle warming trend
through the week.
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&&

.AVIATION...
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041630Z...Coasts/Valleys/Foothills...Low clouds cover the region
west of the mtns, with bases 1800-2200 FT MSL and tops to 3000 ft
MSL. VIS reduced to 1-3SM where low clouds and terrain intersect,
obscuring higher terrain. Expect clearing 17z-20z inland, with
partial clearing near the coast and intermittent CIGs into the
afternoon. Intermittent -SHRA beginning as early as 02-03z Sun at
the coast, but more likely between 06-09z for Orange County/Inland
Empire and 09-12z for San Diego County. Briefly lower CIGs and
slightly reduced VIS down to as low as 3 SM in -SHRA.

Elsewhere...Clear skies with unrestricted VIS this morning, with
increasing high clouds AOA 15,000 FL MSL later today.

Mountains/Deserts...W-SW winds developing after 20z, with the
strongest winds after 00z Sun. Expect W-SW winds 20-35 kt with gusts
of 45-60 kt. Areas of MOD-STG up/downdrafts and LLWS over/east of
mtns.
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&&

.MARINE...
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Gusty northwest wind gusts of 25 to 30 knots will occur this evening
through Sunday evening, which will generate hazardous boating
conditions, especially in the outer waters. Northwest wind gusts up
to 20 knots will be possible over the outer waters each afternoon
and evening for Monday through the middle of next week.
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&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
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CA...Wind Advisory until 8 PM PDT Sunday for Apple and Lucerne
     Valleys-San Bernardino County Mountains-San Gorgonio Pass
     Near Banning.

     Wind Advisory from 3 PM this afternoon to 8 PM PDT Sunday for
     Coachella Valley-Riverside County Mountains-San Diego
     County Deserts-San Diego County Mountains.

PZ...Small Craft Advisory from 3 AM to 10 PM PDT Sunday for Coastal
     Waters from San Mateo Point to the Mexican Border and out
     to 30 nm.

     Small Craft Advisory from 6 PM this evening to 3 AM PDT Monday
     for Waters from San Mateo Point to the Mexican Border
     Extending 30 to 60 nm out including San Clemente Island.
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&&

$$

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AVIATION/MARINE...Adams