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000
FXUS66 KSGX 121659
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
921 AM PDT Fri Apr 12 2024

.SYNOPSIS...
Today will be a little cooler than yesterday, and be followed by
even greater cooling over the weekend as a trough moves across the
region. This trough will bring gusty winds and light showers at
times. Dry weather is forecast next week.

&&

.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
1400-1500 feet. Low clouds extend through the coast and valleys,
and a late morning surge is making its way into the Inland Empire.
Little progress has been made with clearing, but the valleys
should clear through the rest of the morning. The coast will
likely continue to see low cloud cover through most of the day,
with only peeks of sunshine at times.

Temperatures at 9 AM were quite a bit colder than Thursday
morning, with a departure up to 5 degrees cooler at the coast,
mountains and deserts, and 8-20 degrees colder in the valleys.
Highs today will be a few degrees below normal across the coast and
valleys, but up to 5 degrees above normal in the mountains and
deserts. The cooling trend continues through this weekend.

Previous Discussion (Issued 400 AM PDT Fri Apr 12 2024)...
The marine layer was between 1,000 and 1,300 feet deep this
morning, extending to near Chino and Corona in the western Inland
Empire, and to Fallbrook, El Cajon and Ramona in the San Diego
County valleys. The clouds layer was 500-800 ft thick. Clearing
today will be similar to yesterday with the clouds retreating from
the valleys through the morning but lingering near the coast into
the afternoon. The mountains and deserts will be sunny today.

Water vapor imagery showed the center of a compact upper level
circulation 600 miles west of Oregon this morning. This cold core
low will dig south today, and by Saturday morning it will be just
west of SFO. The first of two shortwaves with this trough will track
over Ventura, LA Counties and San Bernardino Counties Saturday
afternoon and evening, bringing a swath of mostly light precipiation
to SoCal during that time. It will first move into the San
Bernardino County Mountains and Orange County, then spread southeast
through the afternoon and evening. Precipitation will be generally
light but with a distinctive north-to-south rainfall gradient. The
highest amounts will be in San Bernardino and Orange County with
lighter amounts in southern San Diego County.

There will be a break in the precipitation Saturday night into
Sunday morning before the second shortwave with a more southerly
trajectory brings a more direct hit to SoCal Sunday afternoon
through Sunday night. Like the first shortwave, this one also
doesn`t have a lot of moisture to work with and the precipitation
amounts will be light. Total rainfall through Sunday night will
range from a few hundredths of an inch to a quarter of an inch in
the coastal and valley areas, from a tenth to a half inch in the
mountains (highest in the San Bernardino Mountains), and less than
0.10" in the high desert.

Snow levels between 5500-6500 feet on Saturday will fall to 4500-
5500 feet Sunday with 2-4" in the San Bernardino Mountains above
6,500 feet.

It will be another cool weekend with gusty winds at times. Sunday
will be the coldest day with highs in the low 60s west of the
mountains, the 30s and 40s in the mountains, and the 50s in the high
deserts. The lower deserts will see highs in the low to mid 70s with
blustery winds and areas of blowing dust and sand at times.

The low moves eastward on Monday with cool, dry northwest flow
through Wednesday keeping temperatures a little below average
through midweek.

&&

.AVIATION...
121535Z...Coast/Valleys...Widespread low clouds in the coastal areas
and valleys this morning, with bases 1000-1500 ft MSL and tops to
3000 ft MSL with areas of VIS 3-5 miles in BR, locally below 1 mile
in fog with areas of terrain obscurations. Most valleys will clear
around 17Z but coastal areas will only have partial afternoon
clearing. Low clouds will be widespread again tonight and Sat
morning with bases 2000-3000 ft MSL and tops to 5000 ft MSL. SCT
-SHRA likely to develop Sat morning.

Mountains/Deserts...Mostly clear skies and unrestricted VIS will
prevail through this evening with terrain obscurations developing on
the lower coastal mountain slopes after 10Z Sat. Areas of west winds
with surface gusts 25-35 kt will develop after 21Z and continue
through Sat morning, with weak up/downdrafts and LLWS over and east
of the mountains.

&&

.MARINE...
No hazardous marine conditions are expected through Saturday, though
showers will occur Saturday, continuing Sunday. Southerly winds
could gust locally to around 20 kts for a brief period on Saturday
afternoon then West wind gusts could locally exceed 20 knots Sunday
and Sunday 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/Moede
AVIATION/MARINE...PG