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Area forecast discussion
National Weather Service San Diego California
241 PM PST Sat Jan 20 2018

Synopsis...
breezy conditions will continue this evening in the wake of a low
pressure system moving from Southern California into Arizona.
There will be slow warming Sunday...with greater warming Monday
through Wednesday with high pressure. Weak offshore flow will
bring gusty northeast winds near the coastal foothills at times.
For next Thursday...another fast moving low pressure system moving
through California will bring cool and windy conditions with a
chance of light precipitation. Then dry with a warming trend
Friday through next weekend as high pressure strengthens near the
West Coast. High surf with strong rip currents will continue this
evening.

&&

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

A departing vigorous upper level trough now moving into Arizona
with subsidence helping to squash out the few remaining rain and
snow showers in socal. Earlier we did have some brief heavy snow
showers in the mountains which dropped a coating of snow on some
mountain roads, causing slippery conditions for travelers. Breezy
conditions will remain early this evening and the wind advisories
will remain in effect until 6 PM. Cool airmass will remain in
place through Sunday with cold temperatures tonight and Sunday
morning with frost likely in the inland valleys.

Ridging the next several days will bring a slow but pronounced
warming trend to the area, especially west of the mountains.
Temperatures will gradually warmup to above normal levels, peaking
in the upper 70s in the valleys on Wednesday.

Another fast moving upper level trough will bring a chance for
mainly light rain and snow to the region Thursday through Thursday
evening. The moisture transport parameters are still quite
marginal with this system so pops were held in check in the chance
category. Beyond Thursday evening, another pattern of upper level
ridging will bring another warmup to the region with benign
weather through next weekend.

&&

Aviation...
202024z...coast...primarily p6sm vis will continue through Sunday
morning with scattered-few cloud decks in the 3000-6000 ft msl layer.

Valleys/coastal mountain slopes/mountain ridges...bkn-sct cloud
decks in the 3000-15000 ft msl layer over the mountains and portions
of the inland valleys (with areas of mountain obscuration) will
gradually become few-scattered through 21/1500 UTC with primarily p6sm vis.

Desert slopes/deserts...through 21/1500 UTC, scattered-few cloud decks in
the 6000-15000 ft msl layer gradually clearing with p6sm vis
expected. Westerly winds 20 to 30 kts with gusts 45 kts into the
evening creating mod-stg up/down drafts over and east of the
mountains.

&&

Marine...
the San Clemente basin buoy has been seeing northwest winds gusting
to 29-33 knots the past several hours with wave heights of around 12-13
feet. Northwest winds of 20-30 kts with gusts to 35 kts will likely
continue over the coastal waters this afternoon, decreasing to 20
kts with gusts 25 kts late this evening. Large wind waves on top of
an elevated swell will create combined seas of 8-14 ft this
afternoon and then gradually subsiding tonight into Sunday. A Gale
Warning continues through 10 PM tonight.

Another storm system may move through the region next Thursday,
possibly bringing another round of strong winds in the coastal
waters and steep seas.



&&

Beaches...
a building fresh swell from a local wind fetch will augment the
large west-northwest swell in place over the coastal waters this
morning, to drive some of the biggest surf of this event. 11 am
observations from the nearshore buoys show 9-12 foot waves at 14
seconds, and surf height observations from lifeguards and surfline
show 6-10 foot surf occurring earlier this morning. Occasional sets
of 12 to 14 feet are likely for exposed west-facing beaches in
southern San Diego County into this afternoon. Elsewhere along the
Southern California coast, 5 to 9 foot surf will continue into this
evening before subsiding later tonight. Strong rip currents will
accompany the high surf, resulting in dangerous swimming conditions.
A high surf advisory continues through 8 PM tonight.

&&

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



&&

Sgx watches/warnings/advisories...
California...Wind Advisory until 6 PM PST this evening for apple and Lucerne
valleys-Coachella Valley-Riverside County mountains-San
Bernardino County mountains-San Diego County coastal areas-
San Diego County deserts-San Diego County mountains-San
Diego County valleys-San Gorgonio Pass near Banning.

Frost advisory from 2 am to 8 am PST Sunday for San Bernardino
and Riverside County valleys-the inland Empire.

High surf advisory until 8 PM PST this evening for Orange County
coastal areas-San Diego County coastal areas.

Pz...Gale Warning until 10 PM PST this evening 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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