Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 230450
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
845 PM PST Mon Jan 22 2018

.SYNOPSIS...
High pressure building aloft will bring warmer days and Santa Ana
weather conditions Tuesday and Wednesday. The Santa Ana winds will
be strongest in the mountains and foothills Tuesday, followed by
lighter winds Wednesday. On Thursday a trough of low pressure will
bring cooler weather along with gusty onshore winds to the mountains
and deserts. On Friday a stronger ridge of high pressure will bring
greater warming next weekend along with more gusty Santa Ana winds.

&&

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

After several cool days with below average temperatures, Tuesday and
Wednesday will warmer, with the greatest warming west of the
mountains under Santa Ana conditions.

A 1034 mb surface high was centered over Utah today which produced
offshore winds gusts to 30 mph in the mountains and passes. The
winds will be stronger Tuesday as the surface high strengthens to
1038 mb, resulting in nearly double digit offshore pressure
gradients. The position of the high is such that it will favor the
strongest winds in the east-west oriented mountain passes including
I-10 through the San Gorgonio Pass and the I-8 corridor through the
San Diego County Mountains. Sustained winds of 15-30 mph are
expected in these areas with gusts from 45-50 mph through mid-
afternoon. On Wednesday the winds won`t be as strong, but still
blustery at times in the Riverside and San Diego County Mountains
and Foothills.

The easterly winds will not be very strong in the valleys or coastal
zones, but the downslope flow and adiabatic warming will bring
several degrees of additional warming. Highs in these areas will be
in the low to mid 70s Tuesday and in the mid to upper 70s Wednesday.
The exception will be the areas within a few miles of the coast
where the afternoon sea breeze will cap the warming. The mountains
and deserts will not see as much of a warm up due to the cooler
northeast flow. Mountain highs will be primarily in the upper 40s
and 50s, the high deserts in the low 60s and the low deserts in the
low to mid 70s.

*From Previous Discussion*

A shortwave trough will pass over Central CA on Thursday. Forecasts
have gained confidence that this system will be moisture starved and
precip should be relegated to Kern County and points north,
therefore we have removed precipitation from our forecast earlier
this morning. Onshore pressure gradients will tighten up Thursday
through Thursday night with strong westerly wind gusts over the
mountains and into the deserts with advisory level winds possible in
these areas along with patchy blowing dust.

Friday through the weekend will feature a strong high pressure
ridge building over the region with a warmup and moderate offshore
flow developing. There could be some gusty offshore winds, peaking
Saturday night and Sunday morning. The stronger ridge will mean
even warmer temperatures into the lower 80s which would be about
15 degrees above normal for this time of the year.

&&

.AVIATION...
230330Z...SKC and unrestricted visibility through 06Z Wednesday.
Areas of LLWS and moderate turbulence will develop through and below
the passes and canyons and along the coastal slopes after 12Z. A
brief period of LLWS below 2,000 ft AGL (around 20 knots) is
possible at KONT or KSNA between 15Z and 19Z Tuesday.

&&

.MARINE...
No hazardous marine weather expected through Wednesday. A trough of
low pressure moving north of the region may bring gusty west
northwest winds and near 10 foot seas to the coastal waters late
Thursday through early Friday.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&

$$

PUBLIC...Moede/Brotherton
AVIATION/MARINE...Albright



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