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Area forecast discussion
National Weather Service San Diego California
938 am PST Tue Feb 21 2017

Synopsis...
slightly warmer today, with a slight chance of showers over
portions of Orange and San Bernardino counties. Cooler and breezy
Wednesday and Thursday with generally dry northwest flow aloft.
Dry and a little warmer Friday and Saturday. Precipitation looks
to return to the area Sunday through Tuesday as two upper-level
troughs move across the area, with gusty winds in the mountains
and deserts at times.

&&

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

At 9 am PST, water vapor satellite imagery displayed an upper-
level trough across central California, and an upper-level ridge
over central baja. Radar showed a small band of elevated showers
moving east northeast across la County into the western San
Bernardino County mountains. Light showers will be possible today
across portions of Orange and San Bernardino counties due to the
elevated moisture moving across the area. Highs today will be a
few degrees warmer than yesterday, which is near seasonal normals
west of the mountains, and around 5 degrees above normal in the
deserts.

A weak upper-level trough will move across the region Wednesday
into Thursday. No precipitation is expected over the area from the
trough, however onshore flow is expected to increase and create
westerly wind gusts of 40-60 mph over the mountains and into
portions of the deserts through the period. Highs will lower back
to below normal Wednesday, and down 5-10 degrees below normal by
Thursday. Mostly zonal flow over the region Friday and Saturday
will maintain the cooler weather for the start of the weekend.

Models are in pretty good agreement with two upper-level lows
merging just off of northern California, and then two associated
troughs moving over Southern California early Sunday through next
Tuesday. Precipitation is expected to be heaviest on Sunday and
Sunday night as a precipitable water plume of around 1.10 inches
moves across the area and upper-level dynamics are most favorable.
Snow levels look to be around 6000 ft Sunday, and lower to
possibly 4000 ft by Tuesday. Gusty southwesterly winds are
possible in the mountains as the first trough moves through, with
highs lowering 5-15 degrees below normal by Sunday. Additional
details are coming in the next few days as models better align on
timing and precipitation amounts.

&&

Aviation...
211600z...VFR will prevail. Clouds will be few-scattered between 1500-4000
feet mean sea level. A mid level cloud deck of 7000-10000 feet will continue
north of San Diego County. Isolated ceilings with bases of around
1500 feet mean sea level will affect the coastal basin after 04z tonight.

&&

Marine...
northwest winds and seas will increase Wednesday and continue
through Thursday. A swell from 280-290 degrees will build in on
Wednesday, peaking at 8-11 feet late Wed afternoon and evening with
a period of 14 seconds. The increasing winds and building swell will
result in hazardous boating conditions and a Small Craft Advisory
will likely be needed for Wednesday afternoon into Thursday.

&&

Beaches...
increasing westerly swell will bring high surf Wednesday and
Thursday. The swell will come in from 280-290 degrees at 14 seconds,
producing high surf late Wednesday with sets reaching 8-10 feet.
A high surf advisory will likely be needed for Wednesday afternoon
into early Thursday. Surf will diminish late Thursday and Friday.

&&

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

&&

Sgx watches/warnings/advisories...
California...none.
Pz...none.
&&

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