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Forecast Discussion for San Diego, CA

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000
FXUS66 KSGX 251800
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
1000 AM PST Mon Jan 25 2021

.SYNOPSIS...A cold low pressure system is currently over the
region, will continue to bring areas of showers, strong gusty
winds, and low elevation snow into this evening with Tuesday and
Wednesday a little warmer. Light precipitation may return as early
as late Tuesday night or Wednesday for areas bordering Los
Angeles County, though widespread precipitation is looking
increasingly likely closer to late Thursday into Friday with drier
conditions for the weekend. Wednesday and Thursday will be a
little warmer, cooler on Friday, then warming to around 5 degrees
below average for Sunday.

&&

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

.Morning Update...

The forecast remains on track this morning as winds continue to be
very gusty at the beaches, especially in San diego County, where
current gusts are above 50 MPH in some spots. Westerly winds will
continue to increase later this morning, peaking early in the
afternoon. Winds will slowly ease for Orange County into the Inland
Empire later this afternoon, but winds will continue to howl for San
Diego County into the deserts for the first half of the night.
Please see High Wind Warnings and Wind Advisory products for more
details.

Showers will continue to become more widespread the southern areas
of our forecast area, especially in San Diego County later this
morning into the afternoon, with snow levels going down to around
2,000 feet. A Winter Weather Advisory has been issued for areas
above 1500 feet across the Inland Empire and above 2000 feet in San
Diego County. Hi-res models continue to show a slow sagging of the
moisture down to the south through tonight. Rain totals look to be
around one quarter of an inch in the San Diego metro. Snow showers
will continue for most areas, tapering off north to south this
afternoon into tonight. Thank you to all those who have provided
your snow reports! Many locations across the San Bernardino`s have
picked up over a foot of fresh powder with this latest system. High
elevation locations in the San Diego County mountains could receive
over one foot of snow when all is said and done with this storm
system.

A brief reprieve looks to be had Tuesday into Wednesday. Another
storm looks to make it into our area by Thursday night into Friday.
This will have a bit higher elevation snow, and more widespread
precipitation.

.SHORT TERM (Today through Wednesday night)...
A cold low pressure system from the northwest will move quickly
through southern California today, moving into Arizona tonight. It
will bring showers, low elevation snow, strong gusty winds, and cold
temperatures today with the precipitation ending from the northwest
tonight and early Tuesday. There is also a slight chance of
thunderstorms today, mainly for the coast and valleys.

There will be strong gusty winds today into tonight with the ECMWF
EFI exceeding the 90th percentile across the coastal waters into the
adjacent coastal areas and the 80th percentile for portions of the
lower deserts from San Diego County into Imperial County. At the
coast, gusts will exceed 45 mph at times and could briefly reach 55
to 60 mph at times in bands of showers as stronger winds aloft are
brought down to the surface. There was a gust to 46 mph at 900 feet
near Laguna Beach with the passage of a band of showers at 3:20 AM
and subsequent gusts to 45 to 50 mph at Solana Beach and Mission
Beach, Upstream, there have been gusts to 59 mph at 1570 feet on
Catalina Island and 76 mph at Santa Barbara Island.

For the mountains and deserts of San Diego County, cross sections
show winds exceeding 50 knots with the strongest and most widespread
winds from late morning through the afternoon with the cross
sections showing the potential for occasional stronger gusts
downstream over the deserts from mountain waves. These occasional
stronger gusts may continue overnight into early Tuesday.

Snow levels near 3500 to 4000 feet early this morning will lower to
2500 to 3000 feet this afternoon and 2000 to 2500 feet tonight with
the lower snow levels toward the north. Snowfall of a few inches is
possible down to around 3500 feet with 4 to 8 inches above 4000 feet
and 8 to 14 inches above 5000 feet. Snowfall could reach 18 inches
on the higher peaks in the San Bernardino Mountains and the
Riverside County mountains and could locally exceed 18 inches on the
highest peaks in the San Diego County mountains.

There will be slow warming for Tuesday and Wednesday, but with
temperatures remaining well below average. The next low pressure
system moving southward off the California coast could bring some
light precipitation at times for areas bordering Los Angeles County
to the east, but the more widespread and heavier precipitation may
not extend much past Santa Barbara County through much of the day on
Thursday.

&&

.LONG TERM (Thursday through Sunday)...
The next round of more widespread precipitation may move through
southwestern California Thursday night and Friday, with
precipitation ending from the northwest Friday night and early
Saturday, Snow levels are not expected to be as low as early this
week, but could still fall to around 4500 feet on Friday.
Rainfall could range from around 1.5 inch at the coast to 2 to 3
inches in the mountains with locally greater amounts with amounts
decreasing from north to south. Next weekend would be dry and a
little warmer, but with Sunday high temperatures remaining around 5
degrees below average.

&&

.HYDROLOGY...
For Orange County into southwestern San Bernardino and western
Riverside Counties, rainfall (and liquid equivalent above the snow
level) will range from one quarter to one half inch at the coast to
1 to 2 inches in the mountains with one quarter inch or less in the
deserts. For San Diego County, rainfall will range from one half to
three quarters of an inch near the coast to 2 to 3 inches in the
mountains with locally greater amounts.

Snow levels will lower to 2000 to 3000 feet this afternoon and
tonight, closer to 1500 feet in the Inland Empire. Snowfall of a few
inches is possible down to around 3500 feet with 4 to 8 inches above
4000 feet and 8 to 14 inches above 5000 feet. Snowfall could reach
18 inches on the higher peaks in the San Bernardino Mountains and
the Riverside Mountains and could locally exceed 18 inches on the
highest peaks in the San Diego County mountains.

Rainfall rates in bands of heavier showers and isolated
thunderstorms could briefly exceed four tenths of an inch per hour
with fast cell movement being a limiting factor. Isolated thunder is
possible today, mainly for portions of the southern coast and
valleys, with the greatest instability for this afternoon over the
coastal waters into adjacent coastal areas.

Local ponding of water and urban flooding is possible near these
heavier showers, especially if they repeatedly track across the same
area, but overall the threat of flooding is low and runoff is
expected be limited.

The next low pressure system moving southward off the California
coast could bring some light precipitation at times for areas
bordering Los Angeles County to the east, but the more widespread
and heavier precipitation may not extend much past Santa Barbara
County through much of the day on Thursday.

The next round of more widespread precipitation may move through
southwestern California Thursday night and Friday, with
precipitation ending from the northwest Friday night and early
Saturday, Snow levels are not expected to be as low as early this
week, but could still fall to around 4500 feet on Friday.
Rainfall could range from around 1.5 inch at the coast to 2 to 3
inches in the mountains with locally greater amounts with amounts
decreasing from north to south.

Runoff potential would be greater due to deeper layer atmospheric
moisture, already moistened ground, melting snow, and higher snow
levels.

&&

.AVIATION...
251630Z...Coast/Valleys...Strong winds are the biggest issue through
this evening. Expect sustained 20-30 kt winds with gusts 35-45 kts
at KSAN through this evening, with AWW in effect until 06Z. At
KCRQ/KSNA, occasional gusts of 25-30 kts are expected. The peak
winds are expected to occur 18-02Z. Winds will gradually begin to
decrease after 04Z tonight. Scattered SHRA with occasional ceilings
of 2500 feet MSL and brief reduction in visibilities to 2-5SM. Best
chance at KSAN/KCRQ. Isolated TSRA possible but timing/coverage too
low to mention in TAFs. SHRA to taper off near KSNA and KONT after
20Z, with occasional scatter out, but SHRA and BKN clouds continuing
at KCRQ and KSAN through 08Z. Showers ending overnight into Tuesday
with greater scattering out.

Mountains...Expect wind gusts in excess of 40 kts to create low
visibility along with MOD/STG UDDFS at times. Periods of +SHSN can
be expected through this evening with occasional terrain
obscuration.

Deserts...Strong winds expected this afternoon. Sustained 20-30 kts
with occasional gusts to 40 kts expected especially from 18-02Z
followed by a significant decrease in wind speeds overnight tonight.
Expect SCT-BKN clouds 3000-6000 feet MSL with periods of -RA this
morning, tapering off after 18Z.


&&

.MARINE...
Gales and hazardous seas will combine with a few thunderstorms to
generate extremely hazardous conditions today through this evening.
A Gale Warning and a Marine Weather Statement contain the hazard
details. Thunderstorms will become less likely tonight and Tuesday,
while wind and sea conditions gradually improve Tuesday. No
additional marine hazards are expected Tuesday night through
Thursday. The next storm could produce hazardous wind conditions
Thursday night and Friday.

&&

.BEACHES...
Very large swells will generate high surf today through Tuesday.
There is also a small chance of thunderstorms and beach lightning
today. Check the High Surf Advisory and Surf Zone Forecast for
details.

&&

.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 10 PM PST this evening for Riverside
     County Mountains-San Bernardino County Mountains-San Diego
     County Mountains.

     High Wind Warning from 6 AM this morning to 7 AM PST Tuesday for
     San Diego County Deserts.

     Wind Advisory from 6 AM this morning to 10 PM PST this evening
     for Apple and Lucerne Valleys-Orange County Coastal Areas-
     Orange County Inland Areas-San Diego County Valleys-San
     Gorgonio Pass Near Banning.

     Winter Weather Advisory until 10 AM PST this morning for Santa
     Ana Mountains and Foothills.

     High Wind Warning from 6 AM this morning to 10 PM PST this
     evening for San Diego County Coastal Areas.

     High Surf Advisory from 6 AM this morning to 6 PM PST Tuesday
     for Orange County Coastal Areas-San Diego County Coastal
     Areas.

PZ...Gale Warning until 10 PM PST Tuesday 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.

&&

$$

PUBLIC/HYDROLOGY...17
AVIATION/MARINE/BEACHES...MM.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

.SYNOPSIS...


&&

.SHORT TERM...


&&

.LONG TERM...


&&

.AVIATION...
251630Z...Coast/Valleys...Strong winds are the biggest issue through
this evening. Expect sustained 20-30 kt winds with gusts 35-45 kts
at KSAN through this evening, with AWW in effect until 06Z. At
KCRQ/KSNA, occasional gusts of 25-30 kts are expected. The peak
winds are expected to occur 18-02Z. Winds will gradually begin to
decrease after 04Z tonight. Scattered SHRA with occasional ceilings
of 2500 feet MSL and brief reduction in visibilities to 2-5SM. Best
chance at KSAN/KCRQ. Isolated TSRA possible but timing/coverage too
low to mention in TAFs. SHRA to taper off near KSNA and KONT after
20Z, with occasional scatter out, but SHRA and BKN clouds continuing
at KCRQ and KSAN through 08Z. Showers ending overnight into Tuesday
with greater scattering out.

Mountains...Expect wind gusts in excess of 40 kts to create low
visibility along with MOD/STG UDDFS at times. Periods of +SHSN can
be expected through this evening with occasional terrain
obscuration.

Deserts...Strong winds expected this afternoon. Sustained 20-30 kts
with occasional gusts to 40 kts expected especially from 18-02Z
followed by a significant decrease in wind speeds overnight tonight.
Expect SCT-BKN clouds 3000-6000 feet MSL with periods of -RA this
morning, tapering off after 18Z.

&&

.AVIATION...


&&

.MARINE...
Gales and hazardous seas will combine with a few thunderstorms to
generate extremely hazardous conditions today through this evening.
A Gale Warning and a Marine Weather Statement contain the hazard
details. Thunderstorms will become less likely tonight and Tuesday,
while wind and sea conditions gradually improve Tuesday. No
additional marine hazards are expected Tuesday night through
Thursday. The next storm could produce hazardous wind conditions
Thursday night and Friday.


&&

.MARINE...


&&

.BEACHES...


&&

.HYDROLOGY...


&&

.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 10 PM PST this evening for Riverside
     County Mountains-San Bernardino County Mountains-San Diego
     County Mountains.

     High Wind Warning until 7 AM PST Tuesday for San Diego County
     Deserts.

     Winter Weather Advisory until 10 AM PST this morning for Apple
     and Lucerne Valleys-Santa Ana Mountains and Foothills.

     Wind Advisory until 10 PM PST this evening for Apple and Lucerne
     Valleys-Orange County Coastal Areas-Orange County Inland
     Areas-San Diego County Valleys-San Gorgonio Pass Near
     Banning.

     Winter Weather Advisory until 6 AM PST Tuesday for San
     Bernardino and Riverside County Valleys-The Inland Empire-
     San Diego County Valleys.

     High Wind Warning until 10 PM PST this evening for San Diego
     County Coastal Areas.

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

PZ...Gale Warning until 10 PM PST Tuesday 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.

&&

$$

PUBLIC...APR
AVIATION/MARINE/BEACHES...Moreland

Previous Forecast Discussions may be found at
NWS San Diego, CA (SGX) Office Forecast Discussions.
(Click 'Previous Version' there to view past versions successively.
Some may differ only in time posted.)

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