Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 252129
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
229 PM PDT Sat May 25 2019

.SYNOPSIS...
For late tonight through Monday morning, a low pressure system from
the north will bring cooling, strong and gusty west winds for the
mountains and deserts, and periods of showers along and west of the
mountains with the snow level lowering to 5500 to 6000 feet for late
Sunday night into Monday morning. Monday afternoon into Wednesday
will be drier with a warming trend. For Wednesday through Friday, a
trough of low pressure will develop near the West Coast and linger
near California. This will maintain a deeper marine layer and bring
small chances for showers, mainly near the mountains, each afternoon.

&&

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

Partly to mostly cloudy skies over our region today with cool
conditions. A low pressure trough remains stationed across Central
CA and Western NV. A deeper and colder upper low is located off
the coast of Washington State. This low will continue to drop
south along the coast through Sunday, then eject E Sunday night
and Monday across the Southern Sierra and Mojave Desert and into
the 4 Corners region by Monday night.

The upper low will deepen tonight and then begin to weaken Sunday
as it moves across California. The forecast track of the low is
not quite ideal for the best lift and instability for our area,
with mainly light precip amounts for the coast and valleys,
between one-tenth to one-quarter inch, and not enough instability
to add thunderstorms to the forecast. However orographics will be
decent along the coastal slopes of the San Bernardino and
Riverside County Mountains so that precip amounts there could be
in the 1-2" range for the highest amounts. Snow levels are
expected to drop on Sunday from near 7000 feet tonight, down to
5500-6000 feet by Sunday evening. Light snowfall is likely above
6000-6500 feet, and a winter weather advisory remains in effect
for the San Bernardino and Riverside County Mountains.

Onshore winds will become strong tonight, peaking by Sunday
afternoon and evening, with the strongest winds through the
mountain passes and along the desert slopes, with gusts of 55-65
mph at times there. Gusty winds along the desert floors both in
the Mojave and Colorado Deserts will be 40-45 mph at times. There
will be the potential for wind blown dust and sand in the deserts,
especially in the lower deserts and the Coachella Valley where
very little or no precipitation will occur. This could aggravate
health conditions and cause travel complications due to reduced
visibility. A wind advisory remains in effect for the mountains
and deserts and we continue to mention potential for dust/sand
impacts in the forecast and in the wind advisory.

The upper low system will slowly exit the region on Monday. Some
lingering showers may continue into mid-morning Monday, mainly in
San Diego County. Some moderation in temperatures will occur
Tuesday and Wednesday as weak ridging is forecast to build into
California from the East Pac. But the ridging will be short lived
as the long wave trough is expected to deepen after Wednesday, and
remain persistent through next weekend across the West. East Pac
ridging will likely strengthen next weekend, but the trough over
the Western States should keep temperatures struggling to nudge
above normal levels, in fact mainly expected to remain at least a
little bit below normal through next weekend across our forecast
area.


&&

.AVIATION...
252030Z...Coast/Valleys...Widespread low clouds with bases around
2500 ft MSL persist at this hour. SCT to locally BKN CIGS will
continue into the afternoon with bases around 2500 ft MSL, becoming
BKN-OVC after 26/04Z and spreading inland to the coastal slopes
tonight. Expect higher terrain obscurations. Isolated -SHRA possible
after 26/06Z with bases 1500-2000 ft MSL and local vis 3-5 miles
during showers. Expect these conditions through Sunday morning.

Mountains/Deserts...Mostly clear with unrestricted vis through this
evening. Coastal mountain slopes becoming obscured in clouds/fog/-
SHRA after 26/04Z. SW to W winds with sfc gusts 30-40 kt along the
mountain crests/desert mountain slopes and below the passes this
afternoon through Sun. MOD-STG UDDFS and LLWS expected over and NE/E
of the mountains.

&&

.MARINE...
No hazardous marine weather is expected through Thursday.


&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Winter Weather Advisory from noon Sunday to midnight PDT Sunday
     night for Riverside County Mountains-San Bernardino County
     Mountains.

     Wind Advisory from 6 AM Sunday to 2 AM PDT Monday for Apple and
     Lucerne Valleys-Coachella Valley-Riverside County Mountains-
     San Bernardino County Mountains-San Diego County Deserts-
     San Diego County Mountains-San Gorgonio Pass Near Banning.

PZ...NONE.
&&

$$

PUBLIC...Brotherton
AVIATION/MARINE...PG


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