Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 211729
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
929 AM 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. 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 9 AM, satellite imagery displayed a cold, upper-level low
centered over central Nevada. Radar showed scattered showers and
isolated thunderstorms across southern CA, with snow levels around
3000 ft. Rare thundersnow is being observed this morning near Big
Bear and Running Springs. A precipitation summary is headlined on
our webpage highlighting rainfall and snowfall amounts as of 7 AM,
and a new one will be issued shortly. Showers will continue today
across the region, especially in San Diego County, and decrease
through the evening. The aforementioned low will continue south
throughout the day, increasing chances for thunderstorms across
the region through the evening. H500 temperatures will dip down to
-33 C this afternoon, which will create a pretty unstable airmass
over the region. Snow levels near 3000 feet will lower to 2500 to
3000 feet this evening and 2000 to 2500 feet overnight.
Additional snow accumulations of 2 to 6 inches, with localized
amounts up to 14 inches on the higher peaks, are expected. A few
snow showers may linger near the mountains on Friday. Westerly
wind gusts to 45 mph are possible, mainly across the San Diego
County Mountains into adjacent deserts.

Additional rainfall for Orange and southwestern San Bernardino
Counties is expected to range from 0.10-0.20 inch near the coast
to 0.50-1.00 inch in the mountains. For San Diego and western
Riverside Counties, additional rainfall is expected to range from
0.30-0.50 inch near the coast to 0.75 to 1.25 inch in the
mountains with additional rainfall in the lower deserts of around
0.10 inch. Locally higher amounts are expected under
thunderstorms, with small hail mixed in with rain.

Patchy frost is possible Friday morning for inland areas and
portions of the low desert as precipitation ends and skies start
to clear. 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...
211600Z...-SHRA across the region, with -SHSN in the mountain areas
today, 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 near KSNA. More scatter out expected overnight from
north to south across the region.

&&

.MARINE...
Winds and building swell will produce hazardous boating conditions
today through the evening. There is a slight chance of thunderstorms
through early 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 this morning into early 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.

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


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