Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 171607

Area Forecast Discussion
National Weather Service San Diego CA
907 AM PDT Sat Mar 17 2018

Mostly light showers will decrease later this morning, with
another round of showers for the late afternoon and evening ending
late tonight. Snow levels will be 4000 to 4500 feet. It will also
be cooler today with gusty southwest to west winds to 45 mph on
the desert slopes of the mountains. Dry and warmer Sunday through
Tuesday. A low pressure system over the eastern Pacific could
bring rain to areas bordering Los Angeles County on Wednesday with
greater chances for rainfall across much of southwest California
for Thursday into early Friday.



A shortwave trough embedded in the mean cyclonic flow aloft
continues to bring bands of showers to portions of SOCAL this
morning, with snow above 4500 ft. In the past 12 hours, several
locations have reported rainfall accumulations of over 0.5 inch,
with at least one location reporting 0.99 inch. Some locations in
the San Bernardino mtns have reported up to 7 inches of snowfall
so far. Expect showers to taper off this afternoon as the
shortwave moves to the east. A second shortwave will bring another
round of organized precip to the region late this afternoon/evening,
before moving away to the east late tonight. Total rainfall will
range from two tenths to one inch near the coast and one half to
one and one half inch in the mountains with locally greater

In the mountains, snow levels near 4000 to 4500 feet early this
morning will rise to 4500 to 5000 feet this afternoon, then lower
to around 4000 feet late tonight. Total snow accumulations of a
trace to 1 inch are expected between 4000 and 5000 feet, 2 to 5
inches from 5000 to 6000 feet, and 5 to 7 inches above 6000 feet
with local accumulations to 10 inches on the highest peaks of the
mountains in San Bernardino and Riverside Counties.

Gusty southwest to west winds will continue into tonight with,
gusts to 45 mph from the mountain ridge top onto the desert slopes.
Strongest gusts to 55 mph are expected for this evening along the
east slopes of the mountains from the San Bernardino Mountains

For Sunday through Tuesday...high pressure aloft will build over
California with a low pressure system farther off the coast,
centered along 140W. This will bring dry weather with a warming

For Wednesday through Friday...the forecast favors the solutions
from the ECMWF and Canadian models. This would bring an initial
round of more significant precipitation for central and
northwestern portions of Southern California for Tuesday night
into Wednesday. Some of that precipitation might extend into areas
bordering Los Angeles County on Wednesday. As the upper trough
off the West Coast begins to move eastward...more significant
precipitation would spread across much of Southern California
Wednesday night and Thursday...decreasing early Friday.


171529Z...Mountains westward...Areas of BKN-OVC clouds based 1500-
3000 feet MSL merging with higher clouds to 10000 feet MSL with
locally heavy showers, mainly through 1800Z this morning and
KOKB- KSDM eastward to the mountains. Local vis 2-4 SM in heavier
showers. At KSAN the risk of low cloud bases briefly below 1000
feet MSL is low-moderate til about 1800Z and low after 1800Z so
confidence in improvement per the TAF is moderate-high.

Otherwise, SCT-BKN cloud layers 1500-5000 ft MSL with higher
layers to near 10000 feet MSL through about 18/1000Z Sunday
morning with isolated to scattered showers spreading south across
the area.

Desert mountain slopes/deserts...west winds 20-30 kt with gusts to
45 kt through 17/2300Z-18/0600Z with strong UDDFS and wind shear.


West-northwest winds 15-25 kt developing this evening through Sunday
morning. A Small Craft Advisory is in effect from 7 PM this evening
through 4 AM Sunday.

Showers will continue at times today through Sunday morning.


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


CA...Winter Weather Advisory until 3 AM PDT Sunday for Riverside
     County Mountains-San Bernardino County Mountains-San Diego
     County Mountains.

PZ...Small Craft Advisory from 7 PM this evening to 4 AM PDT 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.



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