522
FXUS66 KSGX 131757
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
957 AM PST Mon Jan 13 2025

.SYNOPSIS...
Areas of gusty northeasterly Santa Ana winds will expand
southward across the region today, continuing through Wednesday
afternoon. We can expect northeast to east winds gusting 25 to 35
mph, with gusts to 55 mph along and below the coastal slopes of
the mountains. Conditions will remain very dry, even in the
coastal areas. Critical fire weather conditions will spread
southward today and continue through Wednesday afternoon. Onshore
flow will return with weaker winds and cooler days for Friday and
Saturday. There will be a slight chance for light precipitation
for the weekend, mainly west of the mountains.

&&

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

This morning...Sfc pressure gradients remain offshore, with -4.7
mb SAN-LAS. Enough to support northeast winds gusting 25-35 mph,
locally to 55 mph in the favored areas. The dry airmass allowed
for low temperatures locally near or a little below freezing in
portions of the inland valleys earlier. Temperatures are generally
lower than at this time yesterday, especially in the wind-
sheltered areas.

Sfc high pressure in the Great Basin will maintain and strengthen
offshore pressure gradients through Wednesday. This will support
northeast to east winds gusting 25-35 mph and locally to 55 mph
along and below the coastal mtn slopes. Some high resolution model
guidance shows the potential for localized gusts of 70+ mph for a
period of time from Tuesday night through Wednesday morning,
mainly below and several miles on either side of the Cajon Pass.

Conditions will remain very dry through Wednesday, and critical fire
weather conditions will spread southward across the region today with,
continuing through Wednesday afternoon for the mountains, valleys,
inland Orange County, and the San Gorgonio Pass.

High temperatures today will be a little lower than yesterday,
remaining mostly below seasonal averages. Tuesday and Wednesday
will be warmer, with temperatures near or slightly above seasonal
averages in much of the areas west of the mountains. Low
temperatures for wind-sheltered locations in the Inland Empire,
mostly along Interstates 215 and 15 in the southern Inland Empire,
will fall to around 30 degrees or a little lower again late
tonight into Tuesday morning with areas of frost possible.

A closed upper low currently about 100 miles southwest of Point
Conception will continue to retrograde to the southwest, reaching
a position about 850 miles southwest of San Diego by late Tuesday
night/Wednesday morning. It will then begin to move northeast
over SoCal on Friday, becoming an open wave over AZ on Friday as
it gets reabsorbed in the mean westerlies. It will bring a return
of onshore flow, cooler conditions and a return of marine layer
moisture which will begin to spread inland on Friday. A minority
of model ensembles continue to show slight chances for light
precipitation on Sat and Sun but since what little moisture there
is will be restricted to the boundary layer, any precipitation
that falls will be limited to the areas from the coast to the mtn
foothills.

By early next week, the current pattern reasserts itself and we
return to dry conditions with periods of offshore winds.

&&

.AVIATION...
131700Z...Clear skies will continue today and tonight. Areas of
gusty northeast winds 30-40 kts, locally up to 50 kts, will continue
today and into Tuesday mainly in foothills, the northern Inland
Empire, and inland Orange County. Pockets of LLWS and locally strong
up/downdrafts possible in the lee of mountains. A lull of the winds
expected around 06-18z for the valleys/foothills but remain elevated
in the mountains.

&&

.MARINE...
No hazardous marine conditions are expected through Friday.

&&

.FIRE WEATHER...
Areas of gusty northeasterly Santa Ana winds will expand
southward across the area today and continue at times through
Wednesday afternoon, with winds along and below the coastal
slopes of the mountains gusting 25 to 35 mph, locally gusting to
55 mph. There is some local wind guidance that shows gusts for
late Tuesday night into Wednesday morning along the coastal slopes
of the San Bernardino Mountains to the east of the Cajon Pass to
80 mph and along the lower coastal slopes of the San Gabriel
mountains to the west of the Cajon Pass to 90 mph.

Beyond the winds, lowest daytime humidity for inland areas will
fall to around 10 percent each day through Wednesday with poor
overnight recovery. Critical fire weather conditions will spread
southward across the area today with critical fire weather
conditions continuing through Wednesday afternoon for the
mountains, valleys, inland Orange County, and the San Gorgonio
Pass.

A weak low pressure system off the southern California coast could
move inland across southern California and northern Baja late in
the week. Around 75 percent of model solutions remain dry across
southwestern California with around 25 percent having some light
measurable precipitation from the coast to the mountains, with
less than 10 percent showing any significant precipitation. Even
if interrupted briefly late this week, the recent dominant dry
pattern is likely to return early next with high pressure aloft
off the West Coast, dry northerly to northwesterly flow aloft over
the western states, and occasional periods of offshore lower-
level flow across southern California.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Frost Advisory from midnight tonight to 9 AM PST Tuesday for San
     Bernardino and Riverside County Valleys-The Inland Empire.

     Red Flag Warning until 6 PM PST Wednesday for Orange County
     Inland Areas-San Bernardino County Mountains-Including The
     Mountain Top And Front Country Ranger Districts Of The San
     Bernardino National Forest-San Bernardino and Riverside
     County Valleys  -The Inland Empire-San Gorgonio Pass Near
     Banning-Santa Ana Mountains-Including The Trabuco Ranger
     District of the Cleveland National Forest.

     Wind Advisory until 6 PM PST Wednesday for Orange County Inland
     Areas-San Bernardino County Mountains-San Bernardino and
     Riverside County Valleys-The Inland Empire-San Gorgonio
     Pass Near Banning-Santa Ana Mountains and Foothills.

     Red Flag Warning from 4 PM this afternoon to 6 PM PST Wednesday
     for Riverside County Mountains-Including The San Jacinto
     Ranger District Of The San Bernardino National Forest-San
     Diego County Inland Valleys-San Diego County Mountains-
     Including The Palomar And Descanso Ranger Districts of the
     Cleveland National Forest.

     Wind Advisory from 4 PM this afternoon to 6 PM PST Wednesday for
     Riverside County Mountains-San Diego County Mountains-San
     Diego County Valleys.

PZ...None.

&&

$$

PUBLIC/FIRE WEATHER...PG
AVIATION/MARINE...Munyan