Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 201040
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
240 AM PST Tue Feb 20 2018

.SYNOPSIS...
A cold north flow pattern will continue this week with additional
chances for mostly light showers with lower snow levels around
Wednesday into Wednesday night...and again around late Thursday
into early Friday. Dry and a little warmer for next weekend. For
the early to middle part of next week...a trough of low pressure
near the West Coast will bring increasing chances for potentially
more significant precipitation.

&&

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

A longwave trough of low pressure will remain centered over the
western states with shortwaves moving quickly southward along the
western side of the trough near the West Coast. Relatively slight
differences in the track...timing...and intensity of these
systems will have noticeable impacts on the weather that is
ultimately experienced across Southern California. Tracks slightly
farther west would keep most of the precipitation off the coast
while tracks a little farther east would have greater potential to
spread precipitation inland to around the mountains. In any
event...precipitation amounts should be mostly light with coverage
fairly limited. Snow levels will continue to be fairly low...
around 3500 feet. One of these shortwaves could bring some
additional mostly light precipitation around Wednesday into
Wednesday night and another around late Thursday into early
Friday.

In the near term...temperatures in the inland valleys have fallen
into the lower to mid 30s early this morning with the coldest
locations in the mid to upper 20s with temperatures in the upper
deserts mostly in the mid to upper 20s. Ramona has fallen to at
least as low as 24 so far which would be a new record low
temperature for the date. The previous record low temperature for
today for Ramona was 26 in 2006. Temperatures tonight will be not
quite as cold with the areas impacted by frost and freeze
conditions a little smaller.

Dry with a slow warming trend for the weekend...but with high
temperatures remaining below average as the trough of low pressure
over the southwest states weakens.

For the early to middle part of next week...a trough of low
pressure will redevelop a little farther to the west in the
vicinity of the West Coast with continuing more significant
differences among the global models with the details. This will
maintain below average temperatures with increasing possibilities
for potentially more significant precipitation for Southern
California.

&&

.AVIATION...
201000Z...Mostly clear skies and VFR conditions today through
tonight.

&&

.MARINE...
Northwest winds and choppy seas will continue to diminish this
morning. No hazardous marine conditions are expected through early
Thursday, but hazardous winds and seas are likely again Thursday
afternoon through Friday.


&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Frost Advisory from 10 PM this evening to 8 AM PST Wednesday for
     San Bernardino and Riverside County Valleys-The Inland
     Empire-San Diego County Valleys.

     Freeze Warning until 9 AM PST this morning for San Bernardino
     and Riverside County Valleys-The Inland Empire.

     Frost Advisory until 9 AM PST this morning for San Diego County
     Valleys-San Gorgonio Pass Near Banning.

PZ...Small Craft Advisory until 6 AM PST early this morning 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.

&&

$$

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



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