Area Forecast Discussion
Issued by NWS San Diego, CA

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629
FXUS66 KSGX 211042
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
242 AM PST Wed Feb 21 2018

.SYNOPSIS...
After a cold morning, clouds will increase today and lead to a few
light showers from the coast to the mountains, but most likely in
San Diego County. This small chance of light showers will
continue through early Friday morning. Brisk winds are also in the
forecast Thursday, especially in the mountains and deserts.
A fair and warmer weekend is expected before low pressure returns
next week for another chance of showers.

&&

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

It has been a chilly night so far, but increasing clouds have put
the damper on the freeze party. The insulating clouds have stopped
or even reversed the downward temperature trend overnight.
Nevertheless, frost and the more severe freezes are still
happening this morning. The long wave pattern over the globe has
the western U.S. entrenched in a longwave trough. Shortwaves will
rotate through Southern California within this longwave trough for
at least the coming week. Today we get wave number one bringing
us some clouds today. The middle level clouds moving in now will
push on by, but the low clouds now over the ocean will increase
this morning in the coastal basin. That will lead to some light
showers anywhere in the coastal basin and into the coastal slopes
of the mountains this afternoon. Wave number two sags down
Thursday, bringing a similar precip scenario, but this wave has
more wind and dynamic energy, so precip chances continue into
early Friday. Both these waves favor San Diego County for the best
chances of measurable showers. The snow level will be low around
3500 to 4000 feet, but accumulations will be very light. The winds
will be quite strong in the mountains and deserts Thursday and
Thursday night. The winds weaken and turn offshore Friday morning
to flush out the clouds and precip. Weak offshore flow will
continue through the weekend and it looks pretty sunny, although
with cool days and cold nights (not as cold as our last two
nights, however). Next week wave number three sags down the West
Coast with more copious moisture than the previous two. This has
some promise for decent precipitation, but the timing and strength
issues between models decrease our confidence. Either Monday or
Tuesday we`re forecasting winds and precipitation. It`s starting
to look and feel like winter, except for the wet storms.

&&

.AVIATION...
210930Z...Mostly clear skies with unrestricted visibility early this
morning. Increasing clouds over/west of the mountains with bases
2500-3500 ft MSL and tops varying between 5000-8000 ft MSL after
12Z. ISO-SCT light showers developing this afternoon and evening.
Coastal mountain slopes will become obscured in clouds/fog/precip.

&&

.MARINE...
No hazardous marine conditions are expected through Thursday
morning, but hazardous winds and seas are likely again Thursday
afternoon through Friday. Winds and seas will diminish through the
weekend.

&&

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

&&

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

     Frost Advisory until 8 AM PST this morning for Coachella Valley-
     Orange County Inland Areas-San Diego County Deserts-San
     Diego County Valleys-San Gorgonio Pass Near Banning.

PZ...NONE.

&&

$$

PUBLIC...MM
AVIATION/MARINE...Brotherton



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