Area Forecast Discussion
Issued by NWS San Diego, CA

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911
FXUS66 KSGX 102043
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
1242 PM PST Mon Dec 10 2018

.SYNOPSIS...
A subtropical jet overhead kept the skies thick with high clouds
today. A weak trough will drop southeast across the region on
Tuesday, clearing the high clouds, but temporarily increasing the
marine layer and more low clouds. High pressure will rebuild into
the Great Basin behind the trough for the remainder of the week
creating weak Santa Ana conditions with locally gusty offshore winds
below passes and canyons. It will be a little cooler on Tuesday,
then warmer through Friday under fair skies.

&&

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

Satellite imagery at midday showed a thick band of high clouds
streaming east over SoCal. At the same time, a trough was sagging
south offshore near 130W in the water vapor imagery. The sfc
pressure gradient was weak offshore with weak onshore trends. Wind
reports were still mostly light.

A weak (dirty) ridge over the SW today is giving way to a weak
trough over the far EastPac. Both the ECMWF/GFS operational runs
have a small closed low developing over the CA Bight on Tue as this
feature moves SE. No weather develops, but there may be a sfc
reflection in the form of a Coastal Eddy tomorrow. This will likley
deepen the marine layer and should provide more low clouds in the
morning. The higher clouds should thin more tomorrow, so look for
more sun on Tue after any morning low clouds clear.

Surface winds will turn back offshore on Wed as the low drops SE,
and sfc pressures rise over the interior West. Some marine clouds
and humidity will still be with us into Thu morning, but as the
offshore ramps up, this will get ushered back out to sea leaving
fair and dry conditions, along with above average daytime high
temperatures. The offshore flow will get gusty in the usual places
as well (below passes and canyons, and along the coastal foothills).

More high clouds will likely enter the picture again late Fri as a
weak trough passes to the south, but it will stay mild and dry. Low
POPS reenter the picture early next week with the ECMWF and CMC
model runs swinging a trough down the Coast. The GFS keeps the
trough farther inside as an open wave with no precip over SoCal.

&&

.AVIATION...
102030Z...BKN high clouds AOA 20,000 feet MSL with unrestricted vis
will prevail through the period. Low clouds with bases 1500-2000 FT
MSL will likely bring cigs to San Diego County coastal TAF sites
after 07Z. Coverage may be somewhat patchy, particularly in Orange
County. Clearing by 16-17Z Tue with patchy low clouds returning to
the coast Tuesday night.

&&

.MARINE...
No hazardous marine weather is expected through Friday.

&&

.SKYWARN...
Skywarn activation is not needed.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&

$$

PUBLIC...10
AVIATION/MARINE...Rodriguez



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