Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 222155
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
155 PM PST Thu Feb 22 2018

.SYNOPSIS...
Small chances of light showers will continue through early Friday
morning. Brisk winds are also likely this afternoon through
tonight, especially in the mountains and deserts. The weekend
looks fair before low pressure returns next week for cold weather
and showers.

&&

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

At 1 PM PST, water vapor satellite imagery displayed an upper-
level low centered over southeastern Washington and northeastern
Oregon, with an upper-level trough digging across northern
California. Lower heights aloft will continue scattered, light
showers over and west of the mountains through Friday morning.
High temperatures of 5-15 degrees below normal and snow levels
around 4500 ft are expected this afternoon, then snow levels drop
to 3500 ft overnight. A few hundredths of an inch of precip is
expected, with a few tenths of accumulating snow possible in the
mountains. The approaching trough will create breezy west to
southwest winds across the mountains and deserts through 10 AM
Friday morning. A Wind Advisory remains in effect through the
period for gusts of 40-50 mph.

Somewhat warmer weather is expected this weekend, with highs
closer to seasonal normals under northwest flow aloft. Breezy east
to northeast winds will develop overnight Friday and Sunday
nights near the coastal mountain slopes and through mountain
passes, however a quick burst of westerly winds over the mountains
and deserts is expected Saturday night as a trough digs across
the area. Strongest gusts of 45-55 mph are expected with the
trough passage Saturday evening.

Another deeper trough is forecast to move across the area late
Monday through Tuesday. Precip amounts are still uncertain at this
time as the 12Z ECMWF is around 0.50 inches wetter than the GFS.
Latest models show a break in the precip Wednesday afternoon
through Thursday afternoon, then a deeper trough heads our way for
Friday and Saturday of next week. Atmospheric moisture might be in
better supply for this system, so the potential for greater
precipitation accumulations are there. Gusty west to southwest
winds will also likely develop along the mountains and deserts
from the trough, with snow levels starting around 5000 ft.

&&

.AVIATION...
222130Z...SCT-BKN clouds will prevail from the mountains west to the
coast through Fri with mostly ISOLD -SHRA through Fri morning. Cloud
bases will be 2500-4000 ft MSL with tops to 8000 ft MSL with
occasional obscurations in the mountains. Most vis below the clouds
will remain above 6 miles.

SW to W surface winds will increase this afternoon and continue
through Fri morning with areas of 20-30 kt winds and 35-45 kt gusts
in the mountains and deserts, especially the desert mountain slopes
and east of passes. UDDFS/LLWS/rotors will occur at times over and
east of the mountains this afternoon through Fri morning, including
VCNTY KPSP.

&&

.MARINE...
West to Northwest winds 20-25 kt with gusts to 30 kt and combined
seas up to 8-9 ft with steep waves will develop this afternoon and
continue through Friday evening. This will create hazardous boating
conditions. A Small Craft Advisory remains in effect through 8 PM
Friday.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory until 10 AM PST Friday for Apple and Lucerne
     Valleys-Coachella Valley-Riverside County Mountains-San
     Bernardino County Mountains-San Diego County Deserts-San
     Diego County Mountains-San Gorgonio Pass Near Banning.

PZ...Small Craft Advisory until 8 PM PST Friday 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...Maxwell



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