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Area forecast discussion
National Weather Service San Diego California
312 am PST Wed Jan 18 2017

Synopsis...
after a dry day today, a series of storm systems will move
through the region tonight through early Tuesday. Rain and
mountain snow will be heaviest and westerly winds will be
strongest Thursday morning, Friday afternoon and Sunday night,
along with a slight chance of thunderstorms Thursday and Friday.
Dry weather is forecast to follow on Tuesday.

&&

Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
counties...

We have some coastal low clouds and some high clouds to start our
day this morning. High pressure aloft will bring US the last fair
day for a while. Three storms will move through Southern
California in the coming six days. Storm 1 will arrive tonight. It
will begin with an advance wave of light showers this evening,
but then a cold front will bring widespread rain and mountain snow
just before sunrise Thursday and continue through the morning.
Rain and snow will be heavy at times and there is enough
instability for a slight chance of thunderstorms. The snow level
will drop to about 5000 feet. Strong winds will be felt in most
but not all areas. Showers will decrease Thursday afternoon and
evening. Storm 2 arrives Friday. This storm has deeper moisture
and will bring rain and snow that will be heavy at times Friday
afternoon. The steady precipitation will taper off to showers
Friday night and Saturday. The snow level will drop to about 4000
feet Saturday morning. It looks like a break comes Saturday
afternoon and night. On Sunday storm 3 arrives to bring another
round of rain and snow that looks heaviest Sunday night. Initially
some warm air gets into the mix for higher snow levels Sunday
before falling Monday way down to 3500 feet. Soils will very
likely be saturated by this time, so the flood threat will be
greatest with this third storm. Rivers and burn areas will have to
be watched closely for flooding and debris flows. Showers will
continue possibly into Tuesday morning. Rain amounts for all three
storms will be impressive. Here are some preliminary forecast
totals: coast: 2-5 inches, valleys: 3-6 inches, mountains: 6-12
inches on coastal slopes, high desert: 1-3 inches, lower deserts:
0.75-1.5 inches. Total snowfall should be 2-3 feet above 7000 feet
and 10-20 inches above 5000 feet. Several inches can be expected
above 4500 feet, and even a little in the High Desert Monday. The
strong jet stream is forecast to weaken and lift out Tuesday for
fair and warmer weather heading into the middle of next week. Stay
tuned to updates in the forecasts, discussion, and hazard
products in the coming days to understand the risks and impacts
involved with these storms.

&&

Aviation...
181100z...patchy low clouds continue through about 16z this morning
with bases 1000-1500 ft mean sea level. Patchy fog in the valleys this morning
with vis 1-3 sm at times. Low clouds becoming scattered after 16z through
the afternoon. Aft 00z this evening, increasing cloud layers at or above
3000 ft mean sea level and unrestricted vis through this evening. Coastal
slopes of the mountains becoming obscured in clouds/fog this
evening. Rain showers and mountain snow showers becoming likely
after 06z tonight, with isolated thunderstorms after 12z Thursday.

&&

Marine...
a series of Pacific storms will bring strong winds, heavy rain and
large rough seas Thursday through Tuesday. Conditions hazardous to
small craft are likely Thursday, then gale force wind gusts to 35 kt
and very large combined seas of 14-18 ft are likely Friday and
Saturday. Winds and seas will diminish Sunday, then gale force
conditions possible again late Sunday through Monday as another
system moves across the area. A gale watch has been posted for
Friday through Saturday for the coastal waters.

&&

Beaches...
swell will gradually increase Thursday into Saturday creating
periods of high surf. The highest surf will occur Saturday when
waves could be large enough to cause coastal damage, coastal
flooding and beach erosion. Highest sets will be around 12-15 ft.
Swell and surf will decrease Sunday before increasing again Monday.
A beach hazards statement is now in effect through Monday for
the potential for prolonged high surf conditions.

&&

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

&&

Sgx watches/warnings/advisories...
California...Wind Advisory from 10 PM this evening to 4 am PST Friday for
apple and Lucerne valleys-San Diego County deserts-San
Diego County mountains-San Gorgonio Pass near Banning.

High wind watch from late Thursday night through Saturday
morning for apple and Lucerne valleys-San Diego County
deserts-San Diego County mountains-San Gorgonio Pass near
Banning.

Winter Weather Advisory from 10 PM this evening to 4 am PST
Friday for Riverside County mountains-San Bernardino County
mountains.

Winter Storm Watch from late Thursday night through late Friday
night for Riverside County mountains-San Bernardino County
mountains.

Beach hazards statement from Thursday morning through late
Monday night for Orange County coastal areas-San Diego
County coastal areas.

Pz...gale watch from Friday morning through Saturday afternoon 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.

Small Craft Advisory from 4 am Thursday to 10 am PST Friday 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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