000
FXUS66 KSGX 082011
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
111 PM PDT Wed Apr 8 2020

.SYNOPSIS...
A low pressure system centered south of Point Conception will move
very slowly eastward through Friday, then move more rapidly
eastward and weaken for Friday night and Saturday. Periods of
showers will continue into Friday, ending Friday night. Saturday
through Monday will be warmer and drier, but with high
temperatures remaining below average. Then warmer and dry for
Tuesday and Wednesday.

&&

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

The band of precipitation around the east and north sides of the
low have lifted out of our forecast area as the low slowly shifts
east. Colder air aloft associated with the low center is moving
overhead this afternoon, and combined with daytime heating will
lead to greater instability and a chance of heavier showers and
thunderstorms, especially for the coastal and valley areas. While
no lightning has been detected yet, there have been several
reports of small hail in the coastal and valley areas.

The low will move in a counter-clockwise loop tonight through
Friday, first heading towards Las Vegas Thursday morning before
turning around and making a return trip to southeast CA Thursday
night and Friday, finally heading east into AZ Friday night.
Moisture wrapping around the north/northwest side of the low as
it lifts northeast will continue showers over southern CA,
although it now looks like the main band will be positioned over
LA County and areas west, limiting any snow and desert flooding
impacts over San Bernardino County tonight into Thursday. Most of
the area will just continue to see scattered light to moderate
showers Thursday and Friday before it all comes to an end Friday
night. Instability increases Friday afternoon with the upper low
digging south across southeast CA, so added a slight chance of
thunderstorms across much of the area.

High temperatures are expected to be coolest for today and
Thursday with high temperatures for some inland areas 20 to 25
degrees below average. Saturday through Monday is expected to be
mostly dry and a little warmer but with high temperatures
remaining below average. Tuesday and Wednesday are expected to be
dry and warmer with high temperatures possibly warming to around
average.


&&

.AVIATION...
082000Z...Coast/Valleys/Mountains...Periods of SHRA will continue
into Thu AM. SHSN in the mountains above 4500 ft. BKN-OVC cloud
bases will vary between 3000-6000 feet MSL. In areas of RA cigs 1000-
2000 ft MSL and vis 2-5SM possible. Periods of SCT conditions along
the coast possible through 02Z. Higher terrain will be obscured much
of the time. There is a chance of isolated thunderstorms through 00Z
today.

Deserts...BKN-OVC clouds with bases 5000-7000 ft MSL and periods of
RA/SHRA today. Locally bases could drop to 3000-4000 ft MSL with vis
2-5 SM in areas of RA. There is a chance of isolated thunderstorms
over the area through this afternoon. SCT conditions expected after
01Z Thu.

&&

.MARINE...
There is a slight chance of thunderstorms this afternoon and Friday
afternoon. Otherwise, no hazardous marine weather is expected
through Monday.

&&

.BEACHES...
There is a slight chance of isolated thunderstorms this afternoon
and again on Friday afternoon.

&&

.HYDROLOGY...
Through Friday, additional rainfall is expected to range from
around 1 inch near the coast to 1.5 to 2.5 inches in the
mountains, locally up to 3 inches, with one half to three
quarters inch for high deserts, and around one quarter to one
third inch for low desert areas.

The potential for urban and small stream flooding will continue
today along with the possibility of isolated flash flooding with
thunderstorms or where showers track repeatedly across the same
area.

Snow levels will be near 4500 to 5000 feet into Thursday morning,
then rise to 5000 to 5500 feet for Thursday afternoon through
Friday. In the mountains of San Bernardino and Riverside
Counties, additional snowfall of 3 to 6 inches is expected from
4500 to 5500 feet, 6 to 12 inches from 5500 to 6500 feet, 12 to 18
inches from 6500 to 7500 feet, and 18-24 inches on the highest
peaks. In San Diego County, 3 to 6 inches is possible above 5500
feet with 1 to 3 inches down to 5000 feet.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Winter Weather Advisory until noon PDT Thursday for San Diego
     County Mountains.

     Flash Flood Watch until 7 PM PDT this evening for Apple and
     Lucerne Valleys-Coachella Valley-Orange County Coastal
     Areas-Orange County Inland Areas-Riverside County Mountains-
     San Bernardino County Mountains-San Bernardino and
     Riverside County Valleys-The Inland Empire-San Diego County
     Coastal Areas-San Diego County Deserts-San Diego County
     Mountains-San Diego County Valleys-San Gorgonio Pass Near
     Banning-Santa Ana Mountains and Foothills.

     Winter Storm Warning until 5 AM PDT Friday for Riverside County
     Mountains-San Bernardino County Mountains.

PZ...NONE.
&&

$$

PUBLIC/HYDROLOGY...SS
AVIATION/MARINE/BEACHES...CO




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