Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 211134
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
334 AM PST Tue Feb 21 2017

.SYNOPSIS...
A little warmer today. Cooler and breezy for Wednesday and
Thursday with generally dry northwest flow aloft. Dry and a little
warmer Friday and Saturday. For Saturday night through Tuesday...a
pair of low pressure systems are expected to bring cooling with
periods of precipitation...most significant on Sunday and
Tuesday.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

Southwest flow aloft will direct significant moisture and
precipitation into northern and central California today. Greater
cloud cover extends into about the northwest half of Southern
California with cloud cover decreasing further south into San
Diego.

For late Wednesday into Thursday...a trough of low pressure from
the northwest will move inland through California bringing
stronger onshore flow and cooling for Southern California with
gusty west to northwest winds to the mountains and deserts with
advisory strength winds possible for Wednesday night.

For Friday through early next week...the global models are in
better agreement with the evolution of the weather pattern over
the eastern Pacific and the western states though with some
continue lesser differences. On Friday...a low pressure system
will be moving southward off the Pacific Northwest coast with a
close low pressure system to the southwest of that centered near
35N/145W. On Saturday...these two low pressure systems will
merge off the coast of California along 130W...then move inland
through California on Sunday. Another low pressure system moving
southward off the British Columbia coast Saturday...will move
southward and then inland across California Monday night and
Tuesday.

Dry and a little warmer for Friday and Saturday. For late Saturday
night into Sunday night...the first of these systems will bring
precipitation into southwest California with current timing of the
more significant precipitation from late Sunday morning through
early Sunday evening with periods of showers for late Sunday night
through Monday. The second of these systems would bring another
round of more significant but lesser precipitation for late
Monday night into Tuesday.

The first of these systems for Sunday has a feed of subtropical
moisture and favorable upper jet dynamics with the left front
exit region of a 150 knot upper jet streak providing enhanced
lift. Moderate precipitation totals are possible along with
widespread advisory strength winds. The second system for late
Monday night and Tuesday is colder with less available moisture
and no subtropical moisture feed.

&&

.AVIATION...
211000Z...Three layers of variable clouds today. Mainly scattered
low clouds based between 1500-4000 feet msl, some mid clouds 7000-
10000 feet mainly north of San Diego County, and high clouds.
Isolated cigs based around 1500 feet msl in the coastal basin after
04Z tonight.

&&

.MARINE...
Northwest winds and seas will increase Wednesday and continue
through Thursday. The increasing winds and building swell will
result in hazardous boating conditions.

&&

.BEACHES...
Increasing westerly swell will bring high surf Wednesday and
Thursday. Highest surf is expected late Wednesday with some sets
reaching 9 feet. 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...
CA...None.
PZ...None.

&&

$$

PUBLIC...17
AVIATION/MARINE/BEACHES...MM


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