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Area Forecast Discussion
Issued by NWS San Diego, CA
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FXUS66 KSGX 271722
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
922 AM PST Fri Jan 27 2023

.SYNOPSIS...
Fair conditions today and Saturday. Sunday through early next week,
a cold storm system will impact the region bringing rain, low-
elevation mountain snow, and gusty west winds. For the middle to end
of next week, warmer conditions with periods of offshore winds are
expected.

&&

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

Forecast Highlights:
*A winter storm will bring impactful snowfall to elevation 3500 feet
 and above in the mountains Sunday through Monday night.
*The storm will also bring gusty winds and rain to low elevations.
*Warming expected for late next week.

Clear skies across the region this morning, with temperatures at 8
AM running 5 to 25 degrees cooler than this time yesterday. The
Inland Empire and other valley locations are running closer to the
15 to 25 degree cooler mark. Temperatures today will run 5 to 10
degrees warmer than yesterday in the valleys, mountains, and High
Desert with temperatures a few degrees cooler in the low desert and
5 to 10 degrees cooler than yesterday at the coast. We will start to
feel a more widespread influence of the changing weather pattern
tomorrow, with temperatures up to 5 degrees cooler than today and
increased cloud coverage.

Showers and winds will begin to increase ahead of the main storm
system on Sunday. Winds will peak at 40 to 55 mph Sunday into early
Monday over the mountains and into portions of the deserts. The
upper low will move over Southern California Monday bringing a blast
of cold air and more widespread precipitation. Snow levels on Sunday
will be near 5000 feet, dropping to closer to 4500 feet Sunday
afternoon, falling even farther to 3000-3500 feet by Monday
afternoon. Impactful snowfall is expected in the mountains with 6-12
inches likely above 5000 feet. An inch or two of snow is even
possible along I-15 and I-8 through the mountain passes and in
portions of the High Desert. Major travel impacts are expected in
the mountains.

West of the mountains rounds of scattered showers are possible as
early as Sunday morning. Rainfall totals reaching 0.20-0.50 inches
expected west of the mountains at most locales by the time the storm
is finished. Under a tenth of an inch of rain is expected for desert
locations. This system is not tapping into tropical moisture, like
the storms we saw earlier this month so rainfall totals are expected
to be less than what we have been seeing.

The system will move to our east on Tuesday, but cold air will
remain in place. A few showers could linger over San Diego County
mountains Tuesday but most of the region will be dry. A cold morning
is expected on Wednesday, with the potential for widespread frost in
the inland valleys. An upper ridge looks to begin to move in from
the west Wednesday through late next week, leading to dry and warmer
conditions, with periods of offshore winds.

&&

.AVIATION...
271730Z...Coast/Valleys...Clear skies will prevail through this
evening with unrestricted VIS. Areas of stratus will develop near
the immediate coast after 08Z Sat with bases mostly light between
1500 and 2000 ft MSL. Stratus will continue, possibly spreading up
to 10 miles inland after 14Z Sat, and there is about a 30 percent
chance of an MVFR CIG at KSAN between 14Z and 20Z Sat. Local vis 3-5
miles will occur over higher coastal terrain 08Z-20Z Sat.

Mountains/Deserts...Clear skies with unrestricted VIS will continue
through Sat morning.

&&

.MARINE...
No hazardous marine weather conditions are expected through next
Tuesday.

&&

.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...CO
AVIATION/MARINE...Maxwell
National Weather Service Regional Headquarters
