San Diego Weather at Mission Trails, CA

444
FXUS66 KSGX 102137
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
137 PM PST Tue Dec 10 2024

.SYNOPSIS...
Gusty Santa Ana winds will continue in the mountains and valleys
today, weakening through Wednesday morning as weak high pressure
continues to build into the region. This will be quickly replaced
by a trough by later on Wednesday into Thursday, which will bring
in some cooler weather along and west of the mountains. A trough
to the north and a ridge to the east will poise themselves between
SoCal by the weekend and early next week, where the forecast
remains more uncertain.

&&

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

A deep trough that moved over the Desert Southwest has moved into
the Southern Plains, which continues to relax our pressure
gradient and weaken wind speeds. Currently winds have lowered some
across the most wind-prone areas with gusts 50-65 MPH and 20-45
MPH across valley locations. Winds will continue to be gusty
through the afternoon, easing into the night and Wednesday
morning as the ridge axis moves over our region. This will allow
the Red Flag Warning to expire across the mountains and the
valleys, though very dry air will remain in place for the
remainder of Wednesday.

A trough of low pressure off the coast will move closer to
California by Wednesday. This will funnel some sub-tropical
moisture into SoCal by this time, where partly to mostly cloudy
conditions are expected as mid to high level clouds move through
the area. Warmer than average weather will continue into Wednesday
west of the mountains as light offshore flow stays inland, with
slight cooling near the coast as onshore flow begins once again.
We will have to see how deep the marine layer becomes by Thursday
morning for any low cloud development along the coast, though
models do not point to anything significant, partially cloudy
skies are in the forecast. The trough will provide some greater
cooling west of the mountains as onshore flow strengthens and the
marine layer deepens by Thursday. Low clouds and fog will make a
return to the coastal areas and western valleys by Thursday night
and Friday morning as the trough passes through. The weak frontal
boundary and deep marine layer may lead to a stray shower and
drizzle across parts of San Diego County during this time.

By Friday, another weak ridge will form over the Desert Southwest.
Model ensemble guidance puts Southern California in between this
system and another approaching trough that will move into the
Northern California vicinity. Most models keep this trough placed
further north, while a smaller percentage of models make it deep
enough to produce gustier winds and a greater chance of rain. NBM
looks good for drier scenario with minimal chances for rain and
partly sunny conditions.

&&

.AVIATION...
102050Z....Clear skies will prevail today and tonight. Areas of
northeast to east winds will slowly decrease this afternoon,
generally 25-45 kts, strongest in south and west foothills and
below canyons and passes into adjacent valleys. Isolated VIS
reductions in BLDU. Moderate to strong up/downdrafts today over
and in lee (southwest) of mountains and foothills. Winds diminish
this afternoon and evening, but local gusts to 30 kts will
continue into Wednesday morning.

&&

.MARINE...
Easterly winds with occasional gusts to around 20 knots will peak
this morning and decrease this afternoon. No hazardous marine
weather conditions are expected through Saturday.

&&

.FIRE WEATHER...
Gusty winds, low humidity, and dry fuels will lead to critical
fire weather conditions for the valleys, inland Orange County, and
mountains today.

Gusty northeast to east winds will continue this afternoon,
diminishing overnight into Wednesday. Strongest winds will occur
on mountain foothills, through passes, and into adjacent inland
valleys. Gusts 35 to 50 mph are occurring through favored passes
and on mountain foothills, isolated gusts to 60 mph or more
occurring in typically wind prone locations. Gusts of 35 to 50 mph
are expected in the Inland Empire below the Cajon and San
Gorgonio Passes, inland Orange County east of I-5, and in the San
Diego County valleys.

Relative humidity values of 5 to 10 percent for inland areas and 15
to 20 percent at the coast today and Wednesday. Overnight
humidity recovery will be poor tonight, 15 to 30 percent tonight
into Wednesday. Humidity is expected to recover into Thursday
with inland afternoon relative humidity values 15 to 30 percent.
Further humidity recovery is expected into Friday.

&&

.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 4 AM PST Wednesday 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.

PZ...None.

&&

$$

PUBLIC...APR
AVIATION/MARINE...Suk