Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 062006
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
106 PM PDT Thu May 6 2021

.SYNOPSIS...
An upper level trough moving inland over California will result
in stronger onshore flow, higher humidity, and cooler weather
through the weekend. Gusty westerly winds will develop late Friday
into Saturday morning over the mountains and into the deserts.
Gusty winds will continue in these areas into Sunday and Monday
but at lower speeds. Expect a deeper marine layer with more
extensive low clouds and patchy fog well inland each night and
morning. Building high pressure will result in warmer temperatures
and less coastal cloudiness toward the middle of next week.

&&

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

Low clouds have cleared out of most of the area this afternoon,
but the clouds persist along the immediate coast. Expect the
low clouds to surge inland again quickly this evening
overspreading all of the coast, valleys, and Inland Empire
by late evening/overnight. Patchy fog will impact mainly the
inland valleys with visibilities down to 1 mile or lower in a
few spots late tonight.

The tail end of an upper level trough will move across southern
California late Friday into early Saturday, with the main impact
being strong westerly wind gusts across the desert slopes of the
mountains, passes and lower deserts. Have issued a Wind Advisory
for the San Gorgonio Pass area and the San Diego County deserts
for late Friday afternoon through early Saturday morning when
gusts of 45 to 55 mph are expected at times. Areas of blowing dust
can be expected in these areas as well.

The upper trough will push eastward Saturday, but longwave
troughing will persist across the West through the weekend. Will
see a continuation of gusty west winds Saturday afternoon through
Monday for the passes and desert slopes, but at lower speeds than
Friday night. The onshore flow and deeper marine layer will
persist with cooler temperatures and higher humidity levels
lasting through Monday especially from the mountains to the coast.
Will continue to see low clouds move well inland each night with
patchy fog over the inland valleys. Another shortwave drops south
through the base of the upper trough across the area on Monday.
The 12Z operational GFS hints at light marine layer precip Monday,
but this scenario is only supported by about a third of the GFS
ensemble members and none of the ECMWF ensemble members. Kept the
forecast dry as a result.

Longwave troughing shifts east to the Plains by midweek, with weak
upper ridging building across southern California. Expect sunnier
and warmer conditions by Tuesday through Thursday. Raised max
temps this period with readings reaching the 100s over the lower
deserts, and mid 80s to lower 90s over the Inland Empire. Will
unfortunately see a decrease in humidity levels especially for the
mountains and inland valleys this period as well.

&&

.AVIATION...
061930Z...Coast/Valleys...Areas of low clouds lingering at the
immediate coast this afternoon. Bases are 1500-2000 ft MSL with tops
to 2500 ft MSL. Low clouds will spread inland again after 01Z Fri,
reaching the coastal slopes vcnty KSBD by 14Z Fri. Bases will likely
be around 2000 ft MSL with tops near 2500-3000 ft MSL. Areas of vis
1-3 miles on slopes where clouds and terrain intersect. Low clouds
becoming SCT 16Z-18Z Friday.

Mountains/Deserts...Mostly clear with unrestricted vis through
Friday.

&&

.MARINE...
No hazardous marine weather is expected through Monday. An eddy will
persist over the California Bight through early next week, leading
to a prevailing gentle south to southwest breeze over the coastal
waters.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory from 2 PM Friday to 7 AM PDT Saturday for San
     Diego County Deserts-San Gorgonio Pass Near Banning.

PZ...NONE.
&&

$$

PUBLIC...Moreland
AVIATION/MARINE...PG


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