Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 160957

Area Forecast Discussion
National Weather Service San Diego CA
257 AM PDT Fri Mar 16 2018

Tranquil and cool weather will prevail today. Another round of
precipitation will impact Southern California this evening through
the overnight hours. This will be associated with another
shortwave and associated weak surface cold front. Another weak
upper level wave will move by on Saturday night and with residual
moisture present, scattered showers will occur Saturday through
Saturday night. The focus of the precipitation Saturday through
Saturday night will be in the mountains, where snow will fall
above 5000 feet tonight and above 4000 feet Saturday through
Saturday night. Quiet weather will return Sunday through Tuesday
as an upper level ridge builds into the area. A Pacific storm
system looks poised to deliver another round of precipitation to
the area during the second half of the work week, but intensity
and timing still needs refinement.



Tranquil weather will prevail today under cool conditions as we
continue under the influence of a west coast trough/low heights.

The next round of precipitation will arrive this evening into
Orange and San Bernardino, western Riverside Counties then slide
SE overnight. Cold air aloft will lead to convective shower
activity in bands ahead of a weak cold front. This will lead to
some moderate shower activity.

General rainfall amounts are forecast to be at 0.25-0.50" west of
the mountains and 0.75-1.25" along the coastal slopes. Isolated
higher totals are possible as we have seen in the recent precip
events. PW though only maxes out to about 0.60".

The precip will lessen by Saturday morning. However, yet another
shortwave will move by Saturday night. This will lead to scattered
showers, especially in the mountains. Snow levels are forecast to
be at 5000 feet tonight, then falling to 4000 feet by late

A Winter Weather Advisory continues for elevations above
4000 feet with this upcoming precip event. Total forecast snow
accumulations are a trace to 1 inch between 4000-5000 ft, 2 to 5
inches 5000-6000 ft, and 5 to 7 inches above 6000 ft with
localized amounts to 10 inches. Westerly wind gusts of 35 to 45
mph are expected along desert mountain slopes as well.

The trough will finally move out on Sunday and an upper level
ridge will build in Monday-Wednesday, leading to dry weather and
warming temperatures. However, by Wednesday clouds will increase
along with a slight chance of rain ahead of a Pacific storm
poised to deliver yet another round of precipitation to SoCal
during the second half of the work week. Right now models pointing
to Thursday as the brunt of the precip, but will have to monitor
trends to see if this speeds up or slows in timing. Given this timing
uncertainty, kept POPS in check, but no doubt once exact timing
is resolved we will increase POPS as this next system will have a
better moisture tap coming in from the west and likely higher
amounts, though probably not excessive as this looks to be


160915Z...BKN-OVC clouds with bases 2500-5000 ft MSL filling in
along/west of the mountains this morning. Lower cloud bases
scattering out 16-18Z with VFR conditions prevailing during the
afternoon. Bases lowering to 2500 ft MSL again after 17/00Z. Showers
will move into the area around 17/02Z then slowly spread southeast
overnight. Local vis 3-5 SM with bases possibly lowering to 1500 ft
MSL in heavier showers. Coastal mountain slopes will be obscured in
clouds/fog at times through Saturday morning. Otherwise SCT-BKN
clouds AOA 20000 ft MSL and unrestricted vis through tonight.


West-northwest winds gusting 20-25 kt developing Saturday afternoon
through early Sunday morning. Scattered showers returning this
afternoon through Saturday. No hazardous marine weather is expected
Sunday through Tuesday.


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


CA...Winter Weather Advisory from 5 PM this afternoon to 5 AM PDT
     Sunday for Riverside County Mountains-San Bernardino County
     Mountains-San Diego County Mountains.



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