Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 111034
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
334 AM PDT Tue May 11 2021

.SYNOPSIS...
High pressure aloft will bring a warming trend for inland areas
into Wednesday and possibly Thursday with high temperatures
warming to 5 to 10 degrees above average. The marine layer will
moderate the warming for coastal areas. The marine layer will
become a little shallower, but with night and morning low clouds
and fog still spreading into the western valleys for Wednesday and
Thursday mornings. A trough of pressure from the northwest will
move through California on the the weekend. This will spread
cooling inland through Sunday with periods of stronger and gusty
southwest to west winds in the mountains and deserts. The marine
layer will deepen with night and morning coastal low clouds and
fog spreading farther into the valleys and possible onto the lower
coastal mountain slopes by Sunday morning. A warming trend will
begin on Monday.

&&

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

.SHORT TERM (Today through Thursday)...
A trough of low pressure over the Rockies will move into the
plains today with high pressure beginning to strengthen over
California. The marine layer is a little shallower than 24 hours
ago with aircraft soundings Monday evening showing a depth of
around 2500 feet and with some weakening of the inversion over
the past 24 hours ago.

Satellite imagery shows coastal low clouds filling in across the
coastal waters and coastal areas and spreading into portions of
the valleys. The low clouds will continue to spread into portions
of the inland valleys early this morning. The marine layer will
become a little shallower for Wednesday into Thursday with the
low clouds spreading inland into the western valleys.

There will be a warming trend for inland areas into Wednesday, and
possibly into Thursday for the deserts with high temperatures
warming to 5 to 10 degrees above average for inland areas. The
marine layer will moderate the warming for the coast into the
valleys with high temperatures remaining a few degrees below
average.

&&

.LONG TERM (Friday through Monday)...
A trough of low pressure will move to near the West Coast on
Friday, then move southeastward through California over the
weekend, then move east of the area on Monday. For Friday through
the weekend, onshore flow will strengthen and the marine layer
will deepen. Night and morning low clouds and fog will extend
farther into the valleys, and possibly onto the lower coastal
mountain slopes for late Saturday night into Sunday morning.

There remain small chances for some light precipitation from the
deepened marine layer around late Saturday night into Sunday
morning, but ensemble members of the ECMWF and GFS have trended
drier from 24 hours ago and the forecast remains dry for now.

The stronger onshore flow will bring periods of stronger and gusty
southwest to west winds in the mountains and deserts with the
stronger winds for Saturday into Sunday. Winds could gust to
around 45 mph in the windier locations.

There will be a cooling trend for Friday through Sunday with
Sunday high temperatures around 5 degrees below average near the
coast and in the deserts and around 15 degrees below average in
some mountain and inland valley locations. A warming trend will
begin on Monday with Monday high temperatures 5 to 10 degrees
warmer than Sunday in some locations.

&&

.AVIATION...
110930Z...Coast/Valleys...Low clouds with bases 1800-
2200 feet MSL and tops to 2500 feet will cover coastal areas and
some valleys this morning. Vis reduced between those elevations.
Scatter out 16-19Z from inland to coast. BKN patches may persist
along coast during the afternoon. Low clouds with bases around 1200-
1600 feet MSL will begin to spread back inland after 02Z, but with
less extensive coverage into westernmost valleys.

Mountains/Deserts...Mostly clear with unrestricted vis today and
tonight.

&&

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

&&

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

&&

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

&&

$$

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


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