Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 221036
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
236 AM 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...

Areas of frost have surfaced again this morning under mostly
clear skies. But at the same time clouds and even showers are
beginning to develop over the ocean and move into the coast.
Frosty objects could get a light shower to add a coat of ice.
Clouds will gather rapidly today and produce a few showers from
the mountains westward, much like Wednesday. Measurable
precipitation is most likely in San Diego County this afternoon
and evening, and up against the mountains. Today`s upper level
shortwave features good convective instability and wind, but is
lacking in deep moisture so amounts will be light for those areas
getting precip: a few hundredths for the most part, but up to a
third inch in the mountains. Winds will increase this afternoon
and top out this evening before decreasing overnight. Top gusts
will reach 45 to 50 mph along the mountain ridgetops and into the
adjacent desert slopes. Tonight the winds decrease and the flow
turns offshore. That will sweep away the clouds and showers,
leaving most of Friday quite sunny. Clear skies will remain with
us this weekend under offshore flow. Offshore winds are forecast
to get a bit gusty in the foothills during the mornings Saturday
and especially Sunday. Lest you think this is a Santa Ana event,
it will be drawing in cold air from the western U.S. interior.
Temperatures will barely exceed 60 Saturday and 65 Sunday, and
that`s for the warmer lower elevations. The mountains will stay in
the 30s and 40s. Nights will be quite cold with clear skies
allowing heat to escape and sub-freezing temperatures in most
parts of the valleys because they won`t have stirring breezes.
Next week looks pretty wet. Yes, I said it. Our eastern Pacific
high pressure ridge will finally give in to the onslaught of
numerous shortwaves that have eroded its east side along the West
Coast. These have been moisture- challenged because of their path
mostly over dry land. The GFS and Euro models are getting closer
together in depicting a trough of low pressure that is able to
slip out into the ocean and pick up better moisture before moving
into Southern California Monday night. Of course that`s when the
details begin to blur. A few shortwaves could move through this
newly carved out trough and bring several waves of precipitation
lasting most of next week. But so much can happen to the guidance
and promise of precipitation between now and then.

&&

.AVIATION...
221000Z...Increasing clouds this morning with bases 2500-4000 ft MSL
with tops to 8000 ft MSL. ISO-SCT light showers developing after 14Z
and continuing through this evening.

SW to W winds increasing over the mountains and deserts with sfc
gusts 35 to 50 kt along the desert mountain slopes and adjacent
desert foothills after 20Z this afternoon. UDDFS/LLWS/rotors likely
over and east of the mountains Thu afternoon and evening, including
near KPSP.

&&

.MARINE...
West to Northwest winds with gusts 20-30 kt and combined seas of 8-9
ft with steep waves will develop this afternoon 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 from 10 AM this morning to 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 from 2 PM this afternoon to 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...MM
AVIATION/MARINE...Brotherton



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