Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 092046
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
Issued by National Weather Service San Francisco CA
146 PM PDT Thu Apr 9 2020

.SYNOPSIS...
A low pressure system will continue to impact southern California
through Friday, then move more rapidly eastward and weaken by
Friday night into Saturday. Periods of showers and high elevation
snow 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 drier
conditions return by the middle of next week.

&&

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

A mid/upper level low pressure system remains parked over south-
central California and southern Nevada this afternoon with
widespread rain showers and higher elevation snow showers
occurring, especially to the north of the San Diego area. The
center of the low will retrograde back over the Pacific by Friday
morning and continue to produce widespread precipitation over the
region through tonight while becoming more widespread. With PWAT
values near 1.00" advecting inland over the region, precipitation
will be moderate to locally heavy at times. Additionally, snow
levels will remain between 5,500 to 6,000 feet through Friday
afternoon with accumulating snowfall in the mountains of San
Bernardino and Riverside Counties where a Winter Storm Warning
remains in effect through 8 PM Friday. As the core of the low
moves back over southern California, there will be a slight
chance of thunderstorms Friday afternoon given the colder,
unstable air mass aloft.

Precipitation will begin to taper off late in the day Friday as
the upper level low moves east into Arizona. Afternoon
temperatures will warm slightly Friday into the upcoming weekend
as southerly flow returns, yet will remain below seasonal
averages in response to troughing over the West Coast. Warmer and
drier conditions are then likely by Tuesday and Wednesday of next
week as the exiting trough is replaced by high pressure building
over the eastern Pacific.


&&

.AVIATION...
091630Z...Coast/Valleys/Mountains...SCT SHRA will continue this
morning, increasing and becoming more widespread this afternoon
and evening. SCT-BKN Cigs lowering to around 1700 ft MSL with
VSBYS 2-5SM possible with passing showers. Otherwise SCT-BKN cigs
will generally remains around 2500-5000 ft MSL. Higher terrain
will be obscured at times, and SHSN will fall above 4500 feet MSL.

Deserts...Mostly BKN clouds will prevail in the 5000-10000-foot MSL
layer through midday, increasing in the afternoon and possibly
lowering to 3000 feet MSL tonight. Mostly ISOLD -SHRA will occur
through midday, with some increase this afternoon and evening. Vis
could lower to 3-5SM in heavier SHRA.

&&

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


&&

.BEACHES...
There is a slight chance of thunderstorms producing lightning
strikes Friday afternoon.

&&

.HYDROLOGY...
Through Friday, additional rainfall is expected to range from
around 1.50 inch near the coast to 1.50 to 2.50 inches in the
mountains with 0.50 to 0.75" inch for high desert areas and
around 0.25 to 0.50 for low desert areas.

The potential for urban and small stream flooding will increase
this evening and into early Friday along with the possibility of
isolated flash flooding with thunderstorms or where showers track
repeatedly across the same area.

Snow levels will be near 5000 to 5500 feet for tonight into Friday
morning and gradually rise late Friday night. In the mountains of
San Bernardino and Riverside Counties, additional snowfall of 2
to 5 inches is expected from 4500 to 5500 feet, 6 to 8 inches
from 5500 to 6500 feet, 8 to 20 inches from 6500 to 7500 feet,
with total accumulations of greater than 24 inches on the highest
peaks. In San Diego County, 1 to 3 inches is possible above 5500
feet with 1 to 2 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...Flash Flood Watch through Friday afternoon 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 8 PM PDT Friday for Riverside County
     Mountains-San Bernardino County Mountains.

PZ...NONE.
&&

$$

PUBLIC...99
AVIATION/MARINE/BEACHES...99



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