061
FXUS66 KSGX 210501
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
901 PM PST Mon Jan 20 2025

.SYNOPSIS...
Moderate to strong Santa Ana winds and very dry conditions will
continue through Tuesday. A quick break in the wind will occur
Tuesday night into Wednesday. Santa Ana winds will return later
Wednesday evening into Thursday, though weaker than the current
event. An area of low pressure will move in from the north by the
weekend, bringing a chance of precipitation, much cooler weather,
and gusty onshore winds.

&&

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

Key Messages:

- Moderate to strong and potentially damaging Santa Ana winds
  continuing through Tuesday afternoon.

- There is an 80 percent chance of a moderate strength Santa Ana
  event Wednesday night and Thursday.

- There is a 30-60 percent chance of measurable precipitation next
  Saturday and Sunday and a 60-80 percent chance of snow levels
  falling below 4000 ft Sunday morning, increasing to 80-90
  percent Monday morning.


Evening update...
Moderate to strong Santa Ana winds are ongoing this evening. As of
830 PM, Banning hit a peak gust of 83 mph, Sill Hill (San Diego
County Mountains) 77 mph, Keen Ridge (Riverside County Mountains)
75 mph, and Chino Hills (Santa Ana Mountains) 71 mph. Still
expecting winds to continue to increase tonight, gradually
shifting to more of an easterly direction and favoring the San
Gorgonio Pass and San Diego County Mountains and adjacent
foothills/valleys by Tuesday morning while beginning to weaken
elsewhere. Winds for all locations will weaken through the
afternoon Tuesday. The High Wind Warning for the Riverside County
and San Diego County Mountains and the San Diego County Valleys
was moved up to start at 9 PM as winds have already ramped up in
these areas. The High Wind Warnings for all areas now end at 4 PM
Tuesday, earlier than their initial end time of 8 PM as winds now
look to weaken faster.

Otherwise cold tonight in the mountains and high deserts where
temperatures will fall into the 20s, locally into the teens for
the higher mountain valleys, including the Big Bear area.
Elsewhere min temperatures will vary greatly, falling into the low
30s in the colder wind sheltered valleys, but generally upper 30s
to mid 40s elsewhere. The long wave trough covering much of the US
will shift eastward by Wednesday, allowing upper level ridging to
move in from the west, providing warmer days through Friday with
highs 5-10 degrees above normal.


Previous discussion...
Surface pressure gradients restrengthen by late Wednesday into
Thursday, which will provide another round of moderate Santa Ana
winds. This event will be weaker and more confined to the usual
wind prone areas. Confidence is lower on how strong winds will be
in adjacent valleys, but the winds look to have a greater easterly
component, which would favor passes/canyons in Riverside and San
Diego Counties. ECMWF ensembles give Romona peak wind gusts near
40 MPH, though some members have gusts closer to 50 MPH. As the
Santa Ana winds move over the area, temperatures may warm a bit
more by Thursday over the western valleys. NBM probabilities paint
a picture of around a 50-50 chance of seeing highs over 80
degrees from El Cajon to Anaheim to Temecula.

Another deep trough will push into the West by Friday into the
weekend. Models are starting to become in better agreement of an
area of low pressure cutting off from the mean the flow and moving
over our region by the weekend. If this system stays far enough
west, we will see an increased chance of precipitation. Models and
ensembles continue to be wet with measurable precipitation, but how
much is still in question. This system also looks to be a colder
one, so snow levels below 4,000 feet may occur as well. Latest
ensemble clusters are in fairly good agreement of the low sticking
into the area by next Monday, a bit less so by Tuesday.  The low may
stick around even into next Monday, so chances for precip rain in
the forecast for this weekend into early next week.

&&

.AVIATION...
210430Z....Mostly clear skies through Tuesday evening. Strong
east/northeasterly wind gusts 30-40 kts continue this evening,
especially in the foothills, mountains, and mountain passes. A few
corridors in the western valleys and into coastal Orange County are
seeing gusts 20-30 kts. Very strong up/downdrafts remain possible
near the mountains along with localized areas of blowing dust that
could lead to VIS reductions. Gusts decrease in the coasts/valleys
some by 09-12z but stay elevated in the mountains and foothills.
Winds re-intensify after 12z, largely in the mountains and foothills
where gusts 40-55 kts expected, with local gusts near 60 kts. Gusts
begin to gradually decrease after 21z Tuesday.

NWS San Diego is aware of limited communications of observations
from KTRM since January 8th. We are working with the FAA to address
this issue.

&&

.MARINE...
Increasing offshore winds this evening, with gusts up to 25-30 kts
and associated choppy seas, mostly north of La Jolla through San
Clemente Island. Winds and seas will peak overnight, before
gradually diminishing Tuesday morning. A Small Craft Advisory
remains in effect and contains more details. No additional hazardous
marine conditions are expected Tuesday afternoon through Friday.

&&

.FIRE WEATHER...
Moderate to strong Santa Ana winds will continue into Tuesday
afternoon, peaking in intensity tonight into Tuesday morning.
Widespread wind gusts of 35-55 mph will occur across the coastal
slopes of the mountains and into the adjacent valleys, with local
gusts over 75 mph in the favored passes, canyons, and coastal
slopes. Winds will gradual shift to easterly tonight, favoring
the San Diego and Riverside County mountains and adjacent
foothills Tuesday morning. Relative humidity of 10-15% this
evening will see little to no improvement overnight. Extremely
dry weather is expected on Tuesday and Tuesday night with minimum
humidity of 5-8% Tuesday afternoon, potentially remaining in the
single digits in the mountains and foothills into Tuesday night
with poor recovery elsewhere. A period of extreme fire weather
conditions is likely across the coastal slopes, foothills, and
adjacent valleys in San Diego County Tuesday morning due to the
combination of wind gusts in excess of 50 mph and single digit
relative humidity.

Winds will gradually weaken Tuesday evening with weak offshore
flow and dry conditions continuing into Wednesday along the
foothills and passes.

Winds strengthen again Wednesday night into Thursday when there
is an 80 percent chance of a moderate Santa Ana event. These
winds will possibly continue into Friday, though weaker. Relative
Humidity will remain in the single digits to mid teens,
maintaining critical fire weather conditions Wednesday evening
into Thursday, and elevated to near critical conditions on Friday.
A Fire Weather Watch remains in place for 6 PM Wednesday through
6 PM Thursday. Conditions improve greatly Saturday and Sunday with
the return of onshore flow and a 30-60 percent chance of rain and
mountain snow.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Red Flag Warning until 10 PM PST Tuesday for Orange County
     Inland Areas-Riverside County Mountains-Including The San
     Jacinto Ranger District Of The San Bernardino National
     Forest-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 Diego County Inland
     Valleys-San Diego County Mountains-Including The Palomar
     And Descanso Ranger Districts of the Cleveland National
     Forest-San Gorgonio Pass Near Banning-Santa Ana Mountains-
     Including The Trabuco Ranger District of the Cleveland
     National Forest.

     High Wind Warning until 4 PM PST Tuesday for San Bernardino
     County Mountains-San Bernardino and Riverside County
     Valleys-The Inland Empire-San Gorgonio Pass Near Banning-
     Santa Ana Mountains and Foothills.

     High Wind Warning until 4 PM PST Tuesday for Riverside County
     Mountains-San Diego County Mountains-San Diego County
     Valleys.

     Fire Weather Watch from Wednesday evening through Thursday
     afternoon for Riverside County Mountains-Including The San
     Jacinto Ranger District Of The San Bernardino National
     Forest-San Bernardino County Mountains-Including The
     Mountain Top And Front Country Ranger Districts 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-
     San Gorgonio Pass Near Banning-Santa Ana Mountains-
     Including The Trabuco Ranger District of the Cleveland
     National Forest.

PZ...Small Craft Advisory until 10 AM PST Tuesday for Coastal Waters
     from San Mateo Point to the Mexican Border and out to 30 nm-
     Waters from San Mateo Point to the Mexican Border Extending
     30 to 60 nm out including San Clemente Island.


&&

$$

PUBLIC/FIRE WEATHER...SS/APR
AVIATION/MARINE...Munyan