000
FXUS66 KSGX 291728
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
925 AM PST Wed Nov 29 2023

.SYNOPSIS...
A trough of low pressure moving across California will bring cool
weather, gusty mountain and desert winds and chance for showers
tonight through Friday. The best precipitation chances and the
highest rain totals will be in San Diego County. Rain chances and
rain amounts will be lower farther north in Orange, San Bernardino
and Riverside Counties. From Saturday through Tuesday, a ridge of
high pressure building over the Southwest will bring dry weather and
a warming trend.

&&

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

Atmospheric moisture has steadily increased across Southern
California the past two days. On Monday the Precipitable Water on
the NKX sounding was 0.26", on Tuesday it was 0.40", and this
morning it was up to 0.56". By this evening the PWATs will increase
to between 0.70-0.80" in weak moisture advection ahead of a West
Coast trough. As the boundary layer reaches late today and tonight,
the rain chances increase. San Diego County has the best chance for
showers, with lesser chances farther north in San Bernardino,
Riverside and Orange County due the storm trajectory.

The trough axis moves into Arizona tonight, followed by a second
upper level trough that will bring a chance for more showers
Thursday into Friday. As with the first trough the rain chances with
this second wave will be highest in San Diego County and lower
farther north. In fact, some section of inland Orange County and the
Inland Empire may not see any rain at all through Friday, and any
rain that does fall will be light. The best chances for showers in
Orange, San Bernardino and Riverside Counties will be on the west
facing mountains slopes and foothills where 0.05"-0.20" is forecast.

The highest rain totals for this event will be in San Diego County.
In the coastal and valleys areas, rain totals of 0.20"-0.50" are
forecast, with the higher end of this range in those areas in the
path of island banding showers that move ashore from over the
coastal waters. In the San Diego County mountains and foothills,
rain amounts of 0.50"-0.75" are forecast on the orographically
enhanced west facing slopes.

Snow levels will fluctuate between 5500 and 6500 feet with an inch
of snowfall possible above 7000 feet.

Over the weekend the 500 mb flow pattern shifts from weakly cyclonic
to weakly anticyclonic as a ridge over the eastern Pacific builds
over the Southwestern states. Saturday will be a cool day with highs
a few degrees below average in all areas, followed by slow and
steady warming Sunday through Wednesday with sunny, warm days and
clear cool nights.

By Tuesday, coastal and valley highs will be in the 70s and 80s,
mountain highs in the 50s and 60s, high desert highs in the 60s and
lower desert highs from 75 to 80.

&&

.AVIATION...
291700Z... Coast/Valleys...Low cloud coverage gradually increasing
this morning with bases near 1500-3000 feet MSL. -SHRA possible
after 21Z, most likely in San Diego County. Isolated vis down to 4SM
and ceilings near 1000 feet MSL in SHRA. -SHRA look to continue
intermittently into Thursday morning, mostly across San Diego County.

Mountains/Deserts...Westerly winds with gusts 35 to 45 kt over the
mountains, through passes, and into the deserts after 21Z.

&&

.MARINE...
Northwest wind gusts near 20 knots over the outer waters late
Thursday through early Friday, which could produce choppy seas and
hazardous boating conditions. Otherwise, no hazardous marine
conditions are expected through Sunday.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.

&&

$$

PUBLIC...Moede
AVIATION/MARINE...Connolly