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Area forecast discussion
National Weather Service San Diego California
839 PM PST Sat Jan 20 2018

Synopsis...
dry weather returns for all areas Sunday, with a slow warming
trend bringing the region back to above average temperatures by
midweek. Cooler conditions, a slight chance for light showers and
breezy west winds are expected Thursday into Friday as a trough
traverses the region. Warmer and dry for next weekend with a
ridging returning along the West Coast.

&&

Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
counties...

At 830 PM...the trough that brought unsettled weather over the
last 36 hours had pushed eastward, and was centered over northern
Arizona. Northwest flow behind the trough was bringing drying to the
mid and upper levels (evident on the 00z nkx sounding). Skies
were mostly clear over the region, apart from a few cumulus
lingering in southern South Dakota County. Winds were on a downward trend,
with just a few gusts over 20 mph lingering over the
mountains/desert slopes and in the coastal waters.

Predominantly clear skies tonight will allow good radiational
cooling. The best frost potential will be over the southern inland
Empire, where some spots may fall into the upper 20s/low 30s.
This, along with dewpoints in a similar range should lead to
frost formation. Pockets of frost will also be possible in the San
Diego County valleys, though coverage should be less widespread.
Frost isn't anticipated for the Coachella Valley and Borrego area.

Zonal flow should be in place on Sunday, though 500 mb heights
will increase by about 20 dm and 850 temperatures will trend
upward by about 4 degrees c. This will bring a few degrees of
warming to the coast and deserts, with larger jumps of around 8-12
degrees for the mountains (in afternoon highs). High clouds will
be on the increase through the day, and may be of sufficient
thickness to limit frost potential Sunday night.

No real notable weather is expected through midweek, as a ridge
slowly builds over the western U.S. Temperatures will slowly trend
upward through Wednesday, as they return to above average values.

A trough of low pressure forecast to move onshore
Thursday/Friday, bringing the potential for another round of
pitifully light Rain/Mountain snow showers. At this time precipitable water values
in faint ribbon of moisture extending from the central Pacific
are only projected to be around 0.80 inches by the time it reaches
socal, not a good sign. Wind looks more notable at this time,
with gusty west winds possible in the coastal waters and over the
mountains and deserts.

Generally speaking the European model (ecmwf) and GFS suggest a return to ridging
next weekend. This should mean a warming trend and dry weather.
Given this and the CPC outlook for below average precipitation
over the southwest during the 8-14 day period, it looks like we
may be done with meaningful rain for the remainder of the month.

&&

Aviation...
210345z...coast/valleys/mountains...skc-sct030 through Sunday.

Desert slopes/deserts...areas of west winds 20g30 kts on the desert
slopes through 10z with moderate up/down drafts. Otherwise mostly
clear with unrestricted vis through Sunday afternoon.

&&

Marine...
winds at the San Clemente basin buoy were still strong at 7 PM with
northwest winds 19g23kt and wave heights of 11 feet. The winds will
slowly decrease overnight. The Gale Warning will expire at 10 PM
tonight. Large wind waves combined with the high swells will produce
combined seas of 8-12 ft tonight, decreasing Sunday morning.

On Thursday and Friday a Pacific storm will bring another round of
gusty winds and elevated seas.

&&

Beaches...
elevated surf of 4 to 8 feet this evening will gradually lower
tonight. Surf on Sunday will range from 3 to 6 feet with higher sets
to 7 feet at times south of La Jolla.

&&

Skywarn...
Skywarn activation will not be needed this week.



&&

Sgx watches/warnings/advisories...
California...frost advisory from 2 am to 8 am PST Sunday for San Bernardino
and Riverside County valleys-the inland Empire.

High surf advisory until 8 PM PST this evening for Orange County
coastal areas-San Diego County coastal areas.

Pz...Gale Warning 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.

&&

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