Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 191005
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
205 AM PST Sun Nov 19 2017

.SYNOPSIS...
Clear skies will continue strong radiational cooling for the rest
of tonight. This will result in freezing temperatures across the
Mojave Desert...the coldest night of the season thus far in Big
Bear...and patchy radiational fog along the coast. Temperatures
will warm quickly today and be a few degrees above average by
early afternoon. High pressure aloft along the West Coast will
strengthen through Wednesday with a warming trend taking high
temperatures to 15 to 20 degrees above average on Wednesday. Areas
near the coast may cool slightly on Thanksgiving...with cooling
spreading inland for Friday through next weekend as high pressure
aloft along the West Coast weakens and onshore lower level flow
returns.

&&

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

Satellite imagery early this morning shows areas of stratus over
central and southern coastal areas of San Diego County extending
inland to the mesas and far western valleys. Fog has been dense
near the mesas...in the far western valleys...and near other
higher coastal terrain with visibilities not quite as low near sea
level. The local workstation WRF has been handling this well and
shows the stratus gradually eroding from the northeast later
tonight and past sunrise.

Very weak offshore lower level flow combined with the high
pressure aloft is keeping coastal foothill areas and areas below
passes and canyons warmer early this morning while areas without
mixing are a few degrees cooler than 24 hours ago. Temperatures
in portions of the upper deserts will fall to around freezing
early this morning with patchy frost...and areas around Big Bear
will once again fall into the teens. High temperatures for most
areas will not change much for today and Monday from those on
Saturday.

Strengthening high pressure aloft along the West Coast and weak
offshore lower level flow will bring greater warming for Tuesday
and Wednesday with high temperatures Wednesday 15 to 20 degrees
above average. This will push high temperatures into the 90s in
portions of the lower deserts...the valleys...and inland coastal
areas with highs in the 80s extending to near the beaches.

Inland areas will remain similarly warm on Thanksgiving while
coastal areas may cool slightly. For Friday through next
weekend...high pressure aloft along the West Coast will begin to
weaken and onshore lower level flow will return to Southern
California. Cooling will spread inland but with inland high
temperatures still remaining a little above average through next
Sunday.

&&

.AVIATION...
191000Z...Coast/Valleys...Patchy very low clouds (bases 100-400 ft
MSL) and dense fog near the coast and mesas in San Diego County
through 12Z, then likely to push off the coast and dissipate after
12Z, per hi-res models and sat trends. After 13Z or so, P6SM vis and
mostly SKC. Patchy very low clouds and dense fog psbl again late
tonight and early Monday morning near the coast but forecaster
confidence on details is low at this time.

Mountains/Deserts...SCT-BKN clouds AOA 12000 ft MSL with
unrestricted vis through tonight.

&&

.MARINE...
No hazardous marine conditions are expected through Thursday.

&&

.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 Apple and Lucerne
     Valleys.

PZ...NONE.

&&

$$

PUBLIC...17
AVIATION/MARINE...JMB


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