Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 241134
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
332 AM PST Tue Jan 24 2017

.SYNOPSIS...
The large cold low pressure system moving inland through the
western states will bring one more round of more significant
showers and isolated thunderstorms with small hail today...mainly
to San Diego County. With the cold atmosphere...there will be
patchy frost in portions of the Inland Empire early this
morning...and for portions of the inland valleys late tonight into
early Wednesday morning. Dry and slowly warmer for Wednesday and
Thursday. Greater warming for Friday through Monday as high
pressure aloft strengthens near the West Coast...and surface high
pressure over the Great Basin brings periods of offshore flow with
the strongest northeast winds for Friday into Saturday.

&&

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

.SHORT TERM (Today through Thrusday)...
A large cold low pressure system over the western states continues
to move slowly eastward. Overnight...the most widespread showers
have been over San Diego County...with most fairly light in
intensity. But dual-pol data with some of the briefly more intense
showers has shown the possibility of graupel. There have also been
a few light showers in eastern portions of the Inland Empire onto
the adjacent coastal mountain slopes.

One more impulse with slightly colder 500 mb temperatures is
expected to bring enhancement of showers to southwest California
beginning around sunrise and continuing through the
morning...mainly over San Diego County. There is also a slight
chance of thunderstorms with small hail. Widely scattered showers
will continue into the afternoon and are expected to end during
the evening.

With the cold atmosphere in place and some clearing...there could
be some patchy frost in southern and eastern portions of the
Inland Empire early this morning. Patchy frost is also expected
for late tonight into early Wednesday morning for portions of the
Inland Empire and inland portions of the San Diego County
valleys...especially towards the foothills of the mountains.

High temperatures today will be similar to Monday and still quite
cool...mostly 15 to 20 degrees below average. Dry weather is
expected for Wednesday and Thursday with slow warming taking high
temperatures to only 5 to 10 degrees below average on
Thursday...back into the lower 60s near the coast and in the lower
deserts.

&&

.LONG TERM (Friday through Monday)...
High pressure aloft will strengthen near the West Coast for Friday
and Saturday...then slowly weaken and move inland for Sunday and
Monday. Surface high pressure over the Great Basin will bring
periods of offshore flow with gusty northeast winds for Friday
through Monday with strongest winds for Friday into Saturday. High
temperatures will steadily warm for Friday through Monday...
warming to near average on Saturday...and around 5 degrees above
average for Monday. This would push high temperatures into the
lower to mid 70s in coastal...valley...and lower desert areas.

&&

.AVIATION...
241000Z...Scattered to broken clouds 2000-5000 feet msl from coast
to mountains today. Showers and isolated tstorms most likely in San
Diego County and western mountain slopes. Brief vis reductions in
heavy showers and local terrain obscured. Gradually clearing from
north to south tonight after 02Z.

Westerly winds 20-30 kt gusting to 40 kt over the mountain ridges,
desert slopes, through passes/canyons and wind-favored adjacent
desert through 18Z, decreasing thereafter.

&&

.MARINE...
Winds will decrease this morning and combined seas will gradually
diminish later today. A Small Craft Advisory is valid until 6 am
today. Scattered showers and isolated thunderstorms are expected
today. After today, no additional hazardous marine weather is
expected through Saturday.

&&

.BEACHES...
High surf will continue today into Wednesday morning, but gradually
decrease during this time. A high surf advisory remains in effect
into Wednesday morning. There is a slight chance of thunderstorms
today.

High surf is possible Friday in San Diego County as a large long-
period swell arrives.
&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Frost Advisory until 8 AM PST this morning for San Bernardino
     and Riverside County Valleys-The Inland Empire.

     Frost Advisory from 9 PM this evening to 8 AM PST Wednesday for
     San Bernardino and Riverside County Valleys-The Inland
     Empire-San Diego County Valleys.

     High Surf Advisory until 9 AM PST Wednesday for Orange County
     Coastal Areas-San Diego County Coastal Areas.

PZ...None.

&&

$$

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



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