Area Forecast Discussion
Issued by NWS San Diego, CA

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545
FXUS66 KSGX 172129
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
129 PM PST Fri Nov 17 2017

.SYNOPSIS...
Offshore flow will create locally gusty winds Saturday morning
across portions of Orange and San Bernardino Counties. High
pressure aloft will gradually build next week, bringing fair and
much warmer weather heading into the holiday.

&&

.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 a weak
upper-level trough digging across southern CA, and an upper-level
ridge over southern Baja. High temperatures will be a few degrees
above/below seasonal normals today. Patchy fog/low clouds may
develop across portions of the coastal basin this evening.
Offshore flow tonight will help to clear out low clouds that
develop in San Bernardino and Orange Counties by Saturday morning.

Upper-level heights will build slightly through the weekend, which
will help high temperatures to increase a few degrees each day
through Sunday. Patchy frost is possible over portions of the High
Deserts Saturday and Sunday mornings as lows dip into the 30s.
Breezy north to northeast winds will develop tonight through
Saturday morning as cold air filters into the Great Basin. Wind
gusts of 20-30 mph are expected through the Cajon Pass and along
coastal slopes of the Santa Ana mountains. Local gusts to 35 mph
are possible through the period.

By Tuesday, high pressure to the south pushes further north over
our area, and starts to heat things up. Highs will quickly
increase to 5-15 degrees above normal by Wednesday, and continue
through Friday. Weak offshore flow will push dry air towards the
coast, with a shallow marine layer only keeping the beaches cool.
Valleys and areas a few miles inland from the coast will celebrate
Thanksgiving with similar temperatures to the Coachella Valley
and San Diego county deserts, mostly in the mid to upper 80s. Over
the past 10 years, the warmest Thanksgiving for San Diego
International was 85 degrees in 2014. The current forecast has
KSAN at 82 degrees.

&&

.AVIATION...
172115Z...Coast and Valley...BKN100 through 06Z. From 06Z-16Z SCT-
BKN015-025 but with low confidence as to the extent of the
stratus coverage. After 16Z Saturday...becoming mostly clear with
unrestricted visibility.

A weak Santa Ana weather pattern will generate locally gusty
northeast winds of 15-25 KT in and below the Cajon Pass and in the
Orange County mountain passes between 06-20Z Saturday.

Mountains and deserts...West winds 15-30 KT through 06Z, strongest
in the high deserts and on the eastern mountain slopes. After
06Z the winds will shift to the NNE from 10-20 KT with stronger
winds of 15-25 KT in the San Bernardino and Orange County mountain
passes.

&&

.MARINE...
Northwest winds gusts to 20 KT over the Outer Waters late
Saturday afternoon through Sunday. Choppy and rough seas may be
hazardous for Small Craft. Otherwise, no hazardous marine conditions
are expected Monday through Wednesday.

&&

.FIRE WEATHER...
Cool today with high relative humidity. Breezy north to northeast
winds will develop through the Cajon Pass and across coastal
mountain slopes of the Santa Ana mountains tonight through
Saturday morning. Max gusts of 25-35 mph are expected. Afternoon
relative humidity will dip down into the teens for most far inland
areas Saturday through Friday of next week, with a few days
increasing slightly to the 20s. High temperatures will be mostly
near normal this weekend then rise 5-15 degrees above normal
Tuesday through Friday of next week under high pressure aloft.

&&

.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/FIRE WEATHER...JJT
AVIATION/MARINE...Moede



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