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294
FXUS66 KSGX 122213
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
213 PM PST Sun Jan 12 2025

.SYNOPSIS...
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Dry conditions with periods of Santa Ana winds expected through the
middle of the week. Critical fire weather conditions expected for
valleys and the coastal mountain slopes. The end of the week will
bring cooler and cloudier weather. Chances of light rain west of
the mountains for next weekend.
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&&

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

Sunny and dry this afternoon with temperatures in the coastal
areas a few degrees warmer than at this time yesterday but a few
degrees cooler in the inland valleys, mountains and deserts. Santa
Ana conditions producing northeast winds gusting 25-40 mph in the
favored locations. Winds will continue to weaken this afternoon
and evening.

From previous discussion...
Sfc pressure gradients will remain offshore through Wednesday and
humidity will remain low. The dry airmass and lack of cloud cover
will enable efficient radiation cooling overnight so that low
temps in the wind-sheltered valley locations will fall into the
30s for the next few days. Lows in the 20s can be expected in
the High Desert and in the teens and in higher elevation mountain
locations. Highs today for inland areas will be 5 to 10 degrees
below average, with slightly above average temperatures expected
near the coast. That trend will continue through mid-week before
cooler conditions develop for later in the week and next weekend.

For Monday through Wednesday...Most ensemble solutions indicate
the development of a closed upper low retrograding from WA/OR to a
position about 850 miles southwest of San Diego by Tuesday night,
forming a Rex Block with a high north of the low. Meanwhile, sfc
high pressure in the Great Basin will maintain offshore pressure
gradients and Santa Ana conditions for SoCal. See the Fire Weather
section below for more information on the dry, windy conditions.

The majority of solutions show the closed low to the southwest
beginning to move northeast over SoCal by late Thursday, becoming
an open wave over AZ on Friday afternoon as it becomes absorbed in
the mean westerly flow. Most ensemble solutions show slight
chances for mostly light precipitation in SoCal on Sat and Sun.
Since most of the available moisture will likely be concentrated
in the boundary layer, any precipitation will be light and
restricted to the mountain slopes and areas west to the coast.
Numerical model guidance tends to struggle with resolving the
evolution of closed low-latitude lows in this part of the world
so there is significant spread in the model solutions and
consequently much uncertainty in the forecast beyond Thursday.
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&&

.AVIATION...
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122145Z...Mostly clear skies continue through Monday afternoon.
Gusty north to northeast winds of 20-30 kts remain possible this
afternoon/evening for the mountains and potions of the Inland
Empire. Winds gradually decrease this evening/overnight with gusts
20-25 kts more localized to the mountains. Winds ramp back up late
Monday morning into Monday afternoon, spreading back into the Inland
Empire and the Orange County coasts with gusts of 25-35 kts.
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&&

.MARINE...
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Breezy offshore flow increases Monday afternoon, continuing through
Wednesday, with gusts near 15 kts. Otherwise, no hazardous marine
conditions are expected through Friday.
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&&

.BEACHES...
Astronomically high tides of 6-7 feet may produce minor tidal
overflow at susceptible low-lying beach parking lots and boardwalks
Monday morning.

&&

.FIRE WEATHER...
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Santa Ana conditions with northeast winds, gusting 25 to 40 mph
in wind-prone areas, will weaken through this evening. Winds are
strongest on the coastal slopes of the San Bernardino mountains
into the Inland Empire and on the Santa Ana mountains into
portions of inland Orange County. Breezy conditions persist into
Sunday afternoon with northeast winds gusting around 25 to 40 mph
and humidity falling back to 10 to 15 percent, maintaining areas
of critical fire weather conditions. Winds gusts briefly fall
below 35 mph Sunday evening.

Another round of Santa Ana winds is expected for Monday through
Wednesday. Guidance continues to indicate a more easterly
component to the winds, with elevated easterly winds reaching San
Diego County mountains and adjacent valleys by Monday evening.
Winds are currently forecast to peak Tuesday and Wednesday, with
gusts of 45 to 55 mph expected. Relative humidity will remain
around 10 to 15 percent each afternoon inland with poor overnight
recovery in the wind prone areas and thermal belts. Critical fire
weather conditions are expected for all mountain locations, the Inland
Empire, San Diego valleys, and Inland Orange County.

Offshore winds will weaken significantly on Thursday and sea
breezes could develop Thursday afternoon, but humidities will see
no significant increase until Friday. Onshore flow will return in
earnest on Friday, bringing cooler weather and increased
humidity. By the end of next week, there is a potential for a
pattern change to take place, bringing a slight (15 to 35
percent) chance of light precipitation west of the mountains. Some
model solutions indicate a return of dry offshore winds early next
week but uncertainty is high at this time.
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&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
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CA...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.

     Red Flag Warning from 4 PM Monday 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.

PZ...None.
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&&

$$

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