Special Weather Statement, NWS San Diego, CA

Area Forecast Discussion
National Weather Service San Diego CA
955 AM PST Fri Mar 12 2021

.SYNOPSIS...
A low pressure system over southern California will continue to
move slowly east. Another round of more widespread showers and
isolated thunderstorms may move across the area from the north
during the afternoon and evening. Drier with slow warming for the
weekend under weak high pressure. A low pressure system moving
inland through California on Monday will bring cooling, stronger
and gusty west winds in the mountains and deserts, and a slight
chance of showers. Then a warming trend for Tuesday through
Thursday with high temperatures returning to around average on
Wednesday and a little above average on Thursday.

&&

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

Morning Update:

Early morning showers dissipated around daybreak. Dry on the
regional radar except for a few rogue showers near Catalina Island.
The latest trends and high resolution guidance still suggests a good
round of showers from early to mid afternoon through early to mid
evening. The intensity of the showers could be healthy given
instability both aloft and surface driven, however limited moisture
and wind profile would limit convective potential. Would expect
brief heavy burst with any showers that form, along with the risk of
isolated thunderstorms. Snow levels will be low again but daytime sun
angle will limit accumulations on roads except for higher
elevations. No changes were needed to the forecast this morning.

Remainder of previous forecaster discussion (issued 456 AM):

SHORT TERM (Today through Sunday)... A low pressure system centered
over southern California early this morning will continue to move
slowly eastward. Showers moving eastward across the coastal waters
may move locally inland into San Diego County early this morning.
Moisture from the north may spread another round of showers and
isolated thunderstorms southward across the area during the
afternoon and evening.

While the Winter Storm Warning continues for the mountains into this
evening, not much snow is expected this morning. The most likely
time for any additional heavy snowfall would be during the late
afternoon into the evening. Any residual showers should end over San
Diego County early Saturday. High pressure will then bring drying
and warming during the weekend but with high temperatures on Sunday
still around 5 degrees below average.

&&

.LONG TERM (Monday through Thursday)...
For Monday, a trough of low pressure moving inland through
California will bring cooling and stronger and gusty west winds in
the mountains and deserts. There continue to be some amplitude
differences in the bulk of the model ensemble members moving this
low pressure system inland. The current model cycle has greater
support for a more amplified trough which would also bring a slight
chance of light showers.

High pressure over the western states will bring dry weather and
warming for Tuesday and Wednesday with Wednesday high temperatures
around average. That warming may continue into Thursday with timing
differences on a low pressure system moving across the eastern
Pacific toward the West Coast.

&&

.AVIATION...

121700Z...Coast/Valleys/Mountains...SCT SHRA and isolated TSRA
through 20z, diminishing north to south through 03Z Saturday. SCT-
BKN clouds with bases 3000-5000 FT MSL, with bases 1500-2500 FT MSL
and vis 1-4 SM in +RA/TSRA. Reduced vis where clouds interact with
terrain. Low clouds to persist into Saturday morning with SCT-BKN
bases 2500-3500 FT MSL, then clearing out somewhat Saturday
afternoon.

Deserts...SCT-BKN clouds 5000-10000 feet MSL with occasional VCSH
through this evening.

&&

.MARINE...
Scattered showers and isolated thunderstorms will occur across the
coastal waters through this afternoon. Storms will be capable of
producing gusty and erratic winds, small hail and a waterspout. No
additional hazardous marine weather is expected tonight through
Sunday. Strong winds and higher combined seas could bring hazardous
marine conditions Sunday into Monday.

&&

.BEACHES...
Isolated thunderstorms could produce lightning at the beaches
through this afternoon.

&&

.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.

PZ...NONE.

&&

PUBLIC...17/JMB
AVIATION/MARINE/BEACHES...Connolly

Special Weather Statement
National Weather Service San Diego CA
1201 PM PST Fri Mar 12 2021

CAZ048-050-057-122045-
San Bernardino and Riverside County Valleys-The Inland Empire CA-
Santa Ana Mountains and Foothills CA-
San Diego County Inland Valleys CA-
1201 PM PST Fri Mar 12 2021

...SIGNIFICANT WEATHER ADVISORY FOR RIVERSIDE AND NORTH CENTRAL SAN
DIEGO COUNTIES UNTIL 1245 PM PST...

At 1159 AM PST, Doppler radar was tracking a strong thunderstorm 7
miles northwest of Fallbrook. This storm was moving slowly
southeast.

Half inch hail and winds in excess of 30 mph will be possible with
this storm.

Other showers developing through the afternoon may also produce
small hail, gusty winds, and heavy downpours, in the Santa Ana
Mountains and the inland valleys.

Locations impacted include...
Temecula, Fallbrook, eastern Camp Pendleton, Murrieta, Camp Pendleton
North, Santa Rosa Plateau, Rainbow, De Luz, Pechanga Indian
Reservation and Bonsall.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 3340 11740 3358 11731 3352 11703 3327 11716
TIME...MOT...LOC 1959Z 294DEG 4KT 3347 11728

JMB