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Area Forecast Discussion (AFD)

Issued by San Diego, CA (SGX)

                            
000
FXUS66 KSGX 212210
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
210 PM PST Thu Feb 21 2019

.SYNOPSIS... 
Through tonight, a cold low pressure system over the southwest 
states will bring showers with low snow levels. Heavy snowfall 
will occur in the mountains and snow showers may linger near the 
mountains on Friday. Areas of frost and freezing temperatures are
expected tonight for the inland valleys. Saturday through 
Wednesday will be dry with a warming trend with high temperatures 
returning to around average by Tuesday or Wednesday.

&&

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

At 1 PM, satellite imagery displayed a cold, upper-level low 
centered just north of southern CA. Radar showed numerous showers
and isolated thunderstorms across southern CA, with snow levels 
around 2000-3000 ft. A precipitation summary is headlined on our 
webpage highlighting rainfall and snowfall amounts as of noon. 
Showers will continue this afternoon across the region, 
especially in San Diego County, and decrease through the evening. 
The aforementioned low will continue south towards southern CA 
this evening, then move southeast into AZ tonight. Snow levels 
will lower to 2000 to 2500 feet overnight. Additional snow 
accumulations of 2 to 5 inches, with localized amounts up to 8 
inches on the higher peaks, are expected through tonight. A few 
snow showers may linger near the mountains on Friday, with small
accumulations even down to 1500 ft in the San Bernardino County
Mountains. The Winter Storm Warning for the mountains remains in 
effect through 1 AM tonight. Westerly wind gusts to 45 mph are 
possible, mainly across the San Diego County Mountains into 
adjacent deserts through this evening.

Additional rainfall amounts for the coast and valleys will range 
from a trace to 0.10 inches in the deserts, to 0.10 to 0.25 
inches over the coast and valleys, and 0.25 to 0.50 inches over 
the mountains. Locally higher amounts are expected under 
thunderstorms, with small hail mixed in with rain.

Patchy frost is expected Friday morning for inland areas, with
freezing temperatures in portions of the Inland Empire and San
Diego Valleys as precipitation ends and skies start to clear.
A Frost Advisory and Freeze Warning has been issued for tonight
for the inland valleys. 

Heights will slowly build through the weekend into next week, 
which will help high temperatures increase to near seasonal 
normals. Dry weather is expected this weekend through the middle 
of next week, with our next storm possibly arriving next Friday.

&&

.AVIATION... 
212100Z...-SHRA across the region and -SHSN in the mountain areas
this afternoon and evening, with greatest coverage in San Diego 
County. Cloud bases west of the mountains will vary between 2500- 
6000 feet MSL with local cigs to 1500 feet and vis 3-6SM in 
heavier SHRA. Local mountain obscurations in clouds through 
tonight. Thunderstorms are possible through 02Z Friday. Westerly 
winds across mountain ridges gusting 25-35 kts through about 22Z, 
decreasing thereafter. Some scatter out this afternoon and evening
near KSNA. More scatter out expected from north to south across 
the region tonight. 

&&

.MARINE... 
Gusty winds and building swell will produce hazardous boating 
conditions today through the evening. There is a slight chance of 
thunderstorms through this evening. A Small Craft Advisory is in 
effect through 10 PM this evening. No additional hazardous marine 
weather is expected Friday through Monday.

&&

.BEACHES...
Building wind swell will boost surf today into Friday morning. Surf 
of 4-7 FT in San Diego County and 3-6 FT in Orange County. Strong 
rip currents are expected. There is a slight chance of thunderstorms 
late through this evening. 

&&

.SKYWARN... 
Skywarn activation is not requested, but snowfall reports would be
appreciated!

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Winter Storm Warning until 1 AM PST Friday for Riverside County 
     Mountains-San Bernardino County Mountains-San Diego County 
     Mountains.

     Freeze Warning from 10 PM this evening to 9 AM PST Friday for 
     San Bernardino and Riverside County Valleys-The Inland 
     Empire-San Diego County Valleys.

     Frost Advisory from 10 PM this evening to 9 AM PST Friday for 
     Orange County Inland Areas.

PZ...Small Craft Advisory 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.

&&

$$

PUBLIC...JJT
AVIATION/MARINE/BEACHES...Connolly