Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 212028
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
128 PM PDT Sat May 21 2022

.SYNOPSIS...
Unseasonably cool weather through Sunday with low clouds and
fog west of the mountains tonight and Sunday morning, but some
afternoon sunshine is expected. Not nearly as windy in the
mountains and deserts today as it was yesterday but westerly winds
are expected to strengthen for Sunday. High pressure aloft will
bring a warmer spell for Monday through Thursday, with Wednesday
and Thursday likely being the warmest days. The marine layer will
be much shallower with less cloud cover during the nights and
mornings. Slight cooling is expected by the end of next week as a
low pressure trough moves in from the Pacific.

&&

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

This afternoon...Still cloudy at the coast but the inland valleys
are seeing some sunshine. The clouds will continue to clear for a
few more hours before they begin to increase in coverage again. In
some areas, temperatures are higher than at this time yesterday
and in some areas temperatures are lower. The Inland Empire is
significantly warmer than yesterday mostly due to the clouds
clearing.

From previous discussion...
Forecast confidence is moderate to high through next Wednesday as
there is good agreement across model platforms with respect to the
synoptic-scale pattern as well as only modest spread among
ensemble members. After Wednesday, model solutions begin to
diverge significantly. This introduces more uncertainty into the
forecast.

An extensive low pressure trough over the western U.S. will
continue to dominate our weather through Sunday. It will maintain
the cool, northwest flow aloft and continue to bring us a deep
marine layer with widespread low clouds west of the mtns tonight
into Sun morning. Sunday will be a little warmer as the airmass
modifies but temperatures will remain generally a few degrees
below seasonal averages. Onshore pressure gradients strengthen
again on Sun which will bring us more gusty west winds in the mtns
and deserts. Wind gusts of up to 45 knots are likely in the wind-
prone locations.

Monday through Thursday...An amplified high pressure ridge over
the eastern Pacific will expand and shift eastward, with a north-
south axis becoming centered over the western U.S. on Wednesday.
This will bring a warming trend which peaks on Wed with high
temperatures near seasonal averages at the coast and 10-15 degrees
above seasonal averages in portions of the inland valleys where
temps could reach the mid 90s. Temps in the lower deserts will be
in the 101 to 105 degree range. The ridge will also shrink the
marine layer, limiting the low clouds and fog to the coastal
areas during the nights and mornings when patchy dense fog could
develop.

Cooler with increasing clouds and breezy conditions again for
next Fri into Saturday as another low pressure trough moves inland
to our north.

&&

.AVIATION...
211930Z...Partial clearing this afternoon with cloud bases generally
2000-2500 ft MSL or higher. Areas along the immediate coast
including the coastal TAF sites will likely struggle to clear out,
only going SCT-BKN for a few hours at most. Clouds becoming BKN-OVC
again 22/00-03Z with bases lowering back to 1000-1500 ft MSL,
localized areas west of the mountains seeing bases fall to 700-1000
ft with pockets of -DZ. Coastal mountain slopes remaining obscured
in clouds/fog at times through much of Sunday morning.

Elsewhere, mostly clear with unrestricted vis. W-NW winds across
mtns and desert slopes will strengthen after 23Z with gusts 20-35
kt. MOD up/downdrafts possible over and east of the mountains.

&&

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

&&

.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...PG
AVIATION/MARINE...Adams


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