Area Forecast Discussion
Issued by NWS San Diego, CA

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277
FXUS66 KSGX 150457
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
857 PM PST Sat Dec 14 2019

.SYNOPSIS...
Cool and breezy tonight with a few light showers from a passing
trough, mainly in the valleys, foothills and on the west facing
mountain slopes. Sunday will be mostly dry and cool behind the
trough. Gusty gusty northeast winds in the mountains, foothills
and inland valleys Monday through early Wednesday as surface high
pressure builds over the Great Basin. A weak trough will bring a
slight chance of light showers late Wednesday into Thursday.

&&

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

UPDATE...
A couple light showers are ongoing this evening, but the majority
of the forecast area is devoid of precipitation. A few spots in
the San Bernardino Mountains recorded a little over a tenth inch
so far, but most measurable precip elsewhere has only amounted to
a few hundredths. Isolated light showers will continue into Sunday
morning. The 00Z NKX sounding shows the saturated layer only
extends from about 2900-4000 ft, so wouldn`t expect much in the
way of additional accumulation. Main thing tonight will be the
continuation of west winds gusting 40-50 mph and isolated gusts up
to 60 mph. Winds will weaken Sunday morning.

The trough axis passes through late Sunday morning with dry
weather following for the remainder of the day. As for the rest of
the forecast period, any precipitation for Wednesday and Thursday
is still low probability as only a handful of EC and GFS ensemble
members show precipitation, and very little at that. The week of
Christmas certainly looks more favorable as a trough digs much
further south along the West Coast.

PREVIOUS DISCUSSION...
Surface high pressure will build over the Great Basin Monday. The
pressure gradients associated with the 1040 mb high will be
strong enough for a moderate offshore winds in the mountain
passes into the inland valleys. The upper support is weak which
will limit the wind strength. The mountains and deserts will be a
little colder Monday and Tuesday, while the coastal zones and
western valleys will benefit from warm downslope flow and see
highs near 70 degrees both days.

Another shortwave digs down the coast Wednesday and Thursday, with
successive model runs trending weaker and farther north with this
system. It will still be close enough for a chance of showers
Wednesday night into Thursday. Weak ridging Thursday night will
bring mild, dry weather Friday into Saturday.

&&

.AVIATION...
150400Z...Coast/Valleys...BKN-OVC clouds with bases 2000-4000 ft and
tops to 5000 ft with scattered showers through tonight. Showers will
end and clouds will scatter out from north to south between 15-20Z.
Gusty winds to continue through tonight, diminishing by Sunday
afternoon with peak gusts around 25 kts.

Mountains/Deserts...West facing mountain slopes will be obscured in
clouds and fog through 15Z Sunday with scattered showers. Ridgetops
and eastern mountain slopes will be mostly clear with unrestricted
vis through tonight. Gusty west winds in the mountains/passes and
over the desert slopes with gusts to 50 kts through Sunday morning
with strong up/downdrafts and LLWS.

&&

.MARINE...
A large, long period west-northwest swell of 15-17 seconds will
combine with a fresh 7-9 second swell to produce combined seas of 9
to 12 ft through Sunday. West northwest winds will increase over the
outer coastal waters, peaking tonight into Sunday morning with gusts
25 to 30 knots, and locally to 35 knots near San Clemente Island. A
Small Craft Advisory is in effect for all of the coastal waters
through 4 PM Sunday.


&&

.BEACHES...
A High Surf Advisory is in effect through Sunday afternoon for 5-10
ft surf, highest in San Diego County. The pounding surf will
contribute to areas of minor beach erosion during the 6 ft+ morning
high tides.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory until 10 AM PST Sunday 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.

     High Surf Advisory until 4 PM PST Sunday for Orange County
     Coastal Areas-San Diego County Coastal Areas.

PZ...Small Craft Advisory until 4 PM PST Sunday for Coastal Waters
     from San Mateo Point to the Mexican Border and out to 30 nm-
     Waters from San Mateo point to the Mexican Border Extending
     30 to 60 nm out including San Clemente Island.

&&

$$

PUBLIC...SS
AVIATION/MARINE/BEACHES...Connolly



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