Expires:No;;527235
FXUS66 KSGX 261656
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
856 AM PST Tue Jan 26 2021

.SYNOPSIS...
Today will be drier, with some sunshine and continued cooler
temperatures. For Wednesday into Thursday, a low pressure system 
stalled off the coast of California may bring some occasional 
light precipitation to areas bordering Los Angeles County to the 
east. This low pressure system will begin to move eastward on 
Thursday with precipitation becoming widespread across 
southwestern California during the late afternoon and evening. The
precipitation may become heavy at times for Thursday night into 
Friday morning, becoming more scattered in nature by late Friday 
afternoon with activity ending from the northwest Friday night and
early Saturday. Drier weather will be in store with a warming 
trend into early next week with high temperatures on Sunday and 
Monday still a few degrees below average.

&&

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

.Morning Update...
Showers continue to slowly push south across the borderland this
morning with skies mostly clear for many. More snow reports came
in last night, many over a foot across the San Bernardino
Mountains, along with some frost in parts of the Coachella Valley
this morning! Some high clouds may infiltrate the region later 
this afternoon as temperatures remain well below average, though 
winds will continue to be much calmer then yesterday's gusty 
fiesta. The forecast remains on track this morning as we get a bit
of a break for much of today and Wednesday. We will continue to keep
tabs on the next storm system that is slated to impact the area 
later on Thursday into Friday.

&&

.SHORT TERM (Today through Thursday)...
There will be a warming trend for today through Thursday but with
high temperatures Thursday still 5 to 10 degrees below average 
for some inland areas. A low pressure system stalled off the 
California coast will spread precipitation into central and 
portions of southern California. Southwestern California will be 
on the eastern fringe of this moisture for Wednesday into Thursday
with occasional scattered light showers possible for areas 
bordering Los Angeles County to the east. As that low pressure 
system begins to move eastward, more widespread precipitation may 
begin to spread into southwest California late in the day on 
Thursday. 

&&

.LONG TERM (Thursday night through Monday)...
The low pressure system stalled off the coast will begin to move 
eastward on Thursday with precipitation spreading across 
southwestern California during the late afternoon and evening. The
precipitation may become heavy at times for late Thursday night 
into Friday morning, becoming showery Friday afternoon with the 
showers ending from the northwest Friday night and early Saturday.

Near the coast, rainfall could range from around 1.5 inch over
northern Orange County to one inch over southern San Diego County.
For the mountains, rainfall (and liquid equivalent above the snow
level) will range from 2 to 3 inches for the coastal slopes of the
San Bernardino County mountains to 1 to 2 inches for the coastal
slopes of the mountains in Riverside and San Diego Counties.

Snow level will rise to 5500 to 6000 feet on Thursday afternoon,
then lower to 4500 to 5000 feet for Friday afternoon and 4000 to
4500 feet for Friday night. For the mountains in San Bernardino
County, snowfall of 4 to 8 inches is possible above 5000 feet, 8
to 12 inches above 6000 feet, and 12 to 18 inches above 7000 feet
with locally greater amounts. For the Riverside County mountains,
4 to 8 inches of snowfall is possible above 5000 to 5500 feet 
with 8 to 12 inches on the higher peaks. For the San Diego County 
mountains, 3 to 6 inches of snowfall is possible above 5000 feet.

With rising snow levels, snow melt will add the runoff from
rainfall, especially for the San Bernardino County mountains.
Runoff potential will be greater due to deep layer moisture, 
recently saturated ground, melting snow, and higher snow levels. 

Dry weather with a warming trend will follow into early next week
with high temperatures on Sunday and Monday still a few degrees
below average. 

&&

.AVIATION... 
261700Z...The last showers should dissipate by 18Z over southern San 
Diego County, with mostly clear skies prevailing the rest of today 
and unrestricted vis. Clouds will increase tonight, with bases 
mostly above 5000 feet MSL and local mountain obscurations late 
tonight and early Wed. There is a slight chance of -SHRA Wed morning.

&& 

.MARINE...
Winds are decreasing over the coastal waters, and the Gale Warning 
will likely be downgraded to a Small Craft Advisory by midday. Winds 
will continue to decrease, with gusts below 20 knots by mid-
afternoon, though seas could continue to be around 10 feet into 
early evening. The next storm will move through late Thursday night 
and Friday and could bring a period of gusty south winds with the 
onset of the storm.

&&

.BEACHES...
Very large, short-period swells will gradually subside today but 
will continue to bring high surf at least this morning. Elevated 
surf is likely with the next storm system late Thursday through 
Friday, with a 13-14 second swell from 270-280 degrees.

&&

.HYDROLOGY...
A low pressure system stalled off the California coast will begin
to move eastward on Thursday with precipitation spreading across 
southwestern California during the late afternoon and evening. The
precipitation may become heavy at times for late Thursday night 
into Friday morning, becoming showery Friday afternoon with the 
showers ending from the northwest Friday night and early Saturday.

Near the coast, rainfall could range from around 1.5 inch over
northern Orange County to one inch over southern San Diego County.
For the mountains, rainfall (and liquid equivalent above the snow
level) will range from 2 to 3 inches for the coastal slopes of the
San Bernardino County mountains to 1 to 2 inches for the coastal
slopes of the mountains in Riverside and San Diego Counties.

Snow level will rise to 5500 to 6000 feet on Thursday afternoon,
then lower to 4500 to 5000 feet for Friday afternoon and 4000 to
4500 feet for Friday night. With rising snow levels, snow melt 
will add the runoff from rainfall, especially for the San 
Bernardino County mountains. Runoff potential will be greater due 
to deep layer moisture, recently saturated ground, melting snow, 
and higher snow levels. 

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Winter Storm Warning until 6 AM PST early this morning for San 
     Diego County Mountains.

     Frost Advisory until 9 AM PST this morning for Coachella Valley-
     Orange County Inland Areas-San Bernardino and Riverside 
     County Valleys-The Inland Empire-San Diego County Valleys.

     High Surf Advisory until 6 PM PST this evening for Orange County 
     Coastal Areas-San Diego County Coastal Areas.

     Winter Weather Advisory until 6 AM PST early this morning for 
     San Diego County Valleys.

PZ...Gale Warning until 10 PM PST this evening for Coastal Waters 
     from San Mateo Point to the Mexican Border and out to 30 nm-
     Waters from San Mateo point to the Mexican Border Extending 
     30 to 60 nm out including San Clemente Island.

&&

$$

MORNING UPDATE...APR
PUBLIC/HYDROLOGY...17
AVIATION/MARINE/BEACHES...Maxwell