Wildfire and Heat in California, November 11 to 15, 2021

Area Forecast Discussion
National Weather Service San Diego CA
922 PM PST Wed Nov 10 2021

.SYNOPSIS...
Warmer and dry conditions will prevail through the rest of this
week. Santa Ana winds will strengthen Thursday and Friday
mornings, before weakening and becoming more localized Saturday.
Well above average temperatures west of the mountains will close
out the week, with a gradual cooling starting near the coast
Saturday and spreading inland Sunday through early next week.
Marine layer low clouds and fog will be absent until early next
week.

&&

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

Update:

A clear sky is seen across the region. Santa Ana Winds have begun
this evening, but they are light with gusts 20-25 mph below the
mountain passes and canyons. The winds will pick up through
Thursday morning with peak gusts to about 45 mph in the most
wind-prone locales. Drying will occur on the downsloping winds and
a hot days are in store for Thursday and Friday west of the
mountains and across the lower deserts before slow cooling occurs
this weekend, but still warmer than normal. See previous
discussion below for more forecast details.

Previous Discussion:

Key Points:
*Santa Ana winds Thursday through Friday morning.
*Above average temperatures west of the mountains through the
 weekend.
*Elevated to near-critical fire weather conditions through the end
 of the week.

The pressure gradient between San Diego and Tonopah, NV has turned
offshore and will remain offshore through the end of the week. The
offshore gradient will keep marine layer low clouds and fog offshore
for the near future. Santa Ana winds from the northeast to east have
begun with gusts mostly under 30 mph through the Cajon Pass, San
Gorgonio Pass, and along I-8 in the San Diego County Mountains.
These winds will strengthen and become more widespread into Thursday
and Friday morning. Santa Ana winds will be most widespread on
coastal mountain slopes and through passes and canyons. Peak gusts
will be around 45 mph. Winds will be more northeasterly Thursday
becoming more easterly on Friday. Winds will weaken and become more
localized Friday afternoon into Saturday.

A warming trend beginning today will continue through Friday.
Temperatures are expected to be 10 to 15, locally 20 degrees above
average Thursday through Saturday. The surface high over the Great
Basin will continue to move east, causing the Santa Ana winds to
weaken and helping the coast cool Saturday with the return of weak
onshore flow. By Sunday, inland locations will begin to further
cool. That being said, the strength of the high pressure aloft does
not change much through early next week, maintaining "cooler" but
still above average temperatures for most areas through Monday.

Early next week, most global ensembles show a trough of low pressure
moving into the northwest US. There is spread in model solutions in
regards to both timing and amplitude of the trough. The spread in
solutions affects how much cooling will occur each day Monday and
Tuesday and for what areas. This also affects when night and morning
low clouds and fog return to coastal areas. Areas of fog could
return as early as Sunday, with return more likely Monday or
Tuesday, becoming more widespread into Wednesday.

&&

.AVIATION...
110500Z...Coast/Valleys...Mostly clear skies with unrestricted vis
through Thursday. Northeast winds gusting 20-30 knots in the inland
valleys through Thursday morning. Winds will diminish slightly
Thursday afternoon and evening before increasing again Friday
morning. Moderate up/downdrafts and LLWS expected across the far
inland valleys.

Mountains/Deserts...Northeast winds gusting 30-40 knots, locally to
45 knots in the favored passes and canyons, through Thursday
morning. Winds will diminish slightly Thursday afternoon and evening
before increasing again Friday morning. Moderate to strong
up/downdrafts expected over the mountains and coastal slopes.

&&

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

&&

.FIRE WEATHER...
Well above average temperatures, dry conditions, and gusty east to
northeast winds will create elevated to near critical fire weather
conditions Thursday and Friday mornings. Inland Orange County, the
valleys, and lower coastal slopes of the mountains will be the most
impacted. The strongest northeast to east winds will occur along and
near the coastal slopes of the mountains and below passes and
canyons with the strongest gusts to around 45 mph. Winds will begin
to diminish on Friday afternoon with weaker and more localized winds
continuing into Saturday. Temperatures west of the mountains will be
10 to 15, locally up to 20 degrees above average Thursday through
Saturday. Lowest daytime humidity for inland areas will fall to
around 15 to 20 percent for Thursday and Friday and around 10 to 15
percent on Saturday.

Humidity will slowly begin to recover Sunday, with greater recovery
Monday and Tuesday as onshore flow increases. Cooler conditions will
also gradually return.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&

PUBLIC...Gregoria (Update)/CO (Previous Discussion)
AVIATION/MARINE...Connolly