High Wind in California, November 19, 2022

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1154 PM PST Fri Nov 18 2022

.SYNOPSIS...18/857 PM.

A moderate to strong Santa Ana wind event will develop through
Saturday with gusty and potentially damaging winds and critical
fire weather conditions across portions of the Southland. Weak
northeast winds will keep the area warm and dry through mid-week
next week, then warm and windy conditions are possible for
Thanksgiving Day.

&&

.SHORT TERM (TDY-SUN)...18/852 PM.

A moderate to strong Santa Ana wind event is getting underway
across the region this evening. Isolated gusts to 73 mph have
already been observed across the Los Angeles County mountains
this evening. As thermal support flows into the region this
evening, wind gusts should become more widespread across eastern
Ventura and western Los Angeles Counties after midnight and into
Saturday morning.

The latest NAM-WRF solutions are increasing 850 and 950 mb winds
by about 5 knots over the previous run and model forecast guidance
continues to increase winds at KCMA. With NAM-WRF boundary layer
winds now closing in on northeast winds 30-35 knots across
southeastern Ventura County, the high wind warning was expanded
far to the southwest into the southeastern Ventura County valleys
(including the Conejo and Simi Valleys) and into the Santa Monica
mountains and wind speeds were upped slightly to account for the
increase.

Farther to north, locally gusty Santa Lucia winds are already
blowing. More widespread breezy to locally gusty winds are
expected across the Santa Lucia range and into the Central Coast
through Saturday morning, but widespread advisory level winds are
not expected at this time.

In wind-sheltered areas, another cold night is setting up as a dry
mass, clear skies, and lighter winds allow for radiative cooling
processes to be more efficient. Cold temperatures are forecast to
develop and patchy to areas of frost will develop late tonight
across the wind-sheltered areas, such as the San Luis Obispo
County interior valleys, Antelope, Santa Ynez, and Ojai Valleys.

An update to the forecast was issued previously and no further
updates are planned at this time.

***From Previous Discussion***

Overall, 12Z models in good synoptic agreement through the short
term period. At upper levels, inside slider drops across the Great
Basin tonight/Saturday then a weak ridge develops over the area
Sunday/Monday. Near the surface, moderate to locally strong
offshore flow is forecast (with strongest offshore flow on
Saturday).

Forecast-wise, main issue will continue to be wind. With the
inside slider, north to northeast offshore gradients will increase
tonight/Saturday. Current deterministic forecasts indicate LAX-DAG
gradient peaking between -5.8 mb and -7.8 mb Saturday morning.
Also, there is decent upper level wind (950-850 mb winds 30-50
knots) and decent cold advection. These forecast values would
point to a moderate to locally strong Santa Ana wind event for
Ventura/LA counties. Looking at short range ensemble guidance
(HREF, SREF, etc.), this forecast is well supported. Currently, a
HIGH WIND WARNING is in effect for the Santa Clarita Valley and LA
Mountains and WIND ADVISORIES are in effect for the remainder the
Santa Ana wind-prone areas late this evening through Saturday
afternoon. At this time, the current slate of warnings/advisories
look good although there is about a 30% chance that some the
advisories may need to be upgraded to warnings tonight/Saturday
morning. Additionally, there is a decent chance that the Santa Ana
winds will remain strong enough in some areas to warrant WIND
ADVISORIES continuing into Sunday morning (and future shifts will
need to monitor this possibility). Expected peak gusts late
tonight/Saturday are expected to be 40-60 MPH (local gusts to 70
MPH) for the mountains and 30-50 MPH (local gusts to 60 MPH) for
coasts/valleys. For Sunday afternoon through Monday, weak
offshore winds will continue across Ventura/LA counties, but
should not require any sort of non-routine wind products.

For San Luis Obispo and Santa Barbara counties, as usual, the
offshore winds will be weaker through the period. For the
mountains and foothill areas, northeasterly wind gusts of
25-40 MPH are likely this weekend, with the strongest gusts across
the Santa Lucia Range tonight/Saturday morning. So, although
breezy, no advisories are expected at this time.

Other than the wind, no significant issues through the short term
period. The offshore flow will prevent any stratus/fog from
developing, so skies should generally remain mostly clear to
partly cloudy (depending on the amount of cirrus clouds drifting
overhead). As for temperatures, there will be minor day- to- day
variations (due to the amount of offshore flow). However,
generally the coasts and coastal valleys can expect high in the
upper 60s to mid 70s with 60s across interior sections. Overnight
lows will continue to be chilly in wind- sheltered areas and there
could be some frost/freeze issues this weekend.

.LONG TERM (MON-THU)...18/151 PM.

For the extended, deterministic models start out in good agreement
on Tuesday, developing an upper low off the Southern California
coast. However for Wednesday through Friday, the GFS is very
progressive with the low, moving it eastward through the period
and developing a rather impressive ridge over the area. On the
flip side, the ECMWF keeps this upper low spinning over northern
Baja Wednesday-Friday which undercuts the ridge.

Either model would indicate a rather warm period for the area on
Thanksgiving Day and Black Friday with a good chance of high
temperatures west of the mountains climbing into at least the
upper 70s to mid 80s. The difference, and hence the forecast
challenge, will be the amount of offshore flow. The GFS solution
has continued weak offshore flow through the period which would
likely result in weak offshore winds. The ECMWF idea would result
in much more upper level support, leading to the potential for at
least moderate offshore winds and warmer temperatures. Current
look at respective ensemble mean forecasts from both models
indicate the forecast would lean towards the GFS idea of a ridge
entrenched over the area and weaker offshore flow. Will definitely
need to continue to watch this situation closely (ensemble
forecasts and cluster analysis) to see how the forecast will
develop. However, again, there is the potential for some warm and
windy conditions for Thanksgiving Day and Black Friday.

&&

.AVIATION...19/0753Z.

At 06Z, there was no marine layer at KLAX. However, there was a surface
based inversion. The top of the inversion was around 1600 ft with a
temp of 17C.

Clear skies with VFR conds expected across the forecast area thru
the period except for some local VLIFR to LIFR cigs/vis through
10Z across portions of the Central Coast.

There will be areas of strong and gusty NE winds across much of
Los Angeles and Ventura Counties overnight through Sat afternoon
with some moderate to strong LLWS and turbulence, and mdt to stg
UDDF near the higher terrain.

KLAX...High confidence in VFR conditions through the period.
There is a 20% chance of east to northeast winds between 9 and 12
knots between 11Z and 17Z Sat. There is a 30 percent chance of
moderate wind shear turbulence and low-level wind shear between
09Z and 17Z Sat.

KBUR...High confidence in VFR conditions thru the period. Moderate
to possible LLWS and turbulence expected through noon or so.

&&

.MARINE...18/747 PM.

For the Outer Waters, moderate to high confidence in current
forecast. Moderate confidence in Small Craft Advisory (SCA) level
northwest winds through this evening over the southern waters
(PZZ676). For later tonight through Saturday, there is a 70%
chance of SCA level northeast winds across PZZ676 with winds and
seas remaining below SCA elsewhere. For Sunday through Wednesday,
high confidence in winds and seas remaining below SCA levels for
all of the outer waters.

For the Inner Waters north of Point Sal, high confidence in
current forecast as winds and seas are generally expected to
remain below SCA levels through Wednesday.

For the Inner Waters south of Point Conception, moderate to high
confidence in the current forecast. Winds will increase to SCA
levels between 03z and 06z. From 06z until tomorrow afternoon,
northeast winds will strengthen further to GALE FORCE across the
waters nearshore from Ventura south to Santa Monica and out past
Anacapa Island. There is a 30 percent chance winds may only reach
strong SCA until late tonight/early Saturday morning. There is
also is a 20% chance winds only remain strong SCA levels. Steep
and choppy seas will accompany the winds across the waters. For
Saturday night through Wednesday, high confidence in winds and
seas remaining below SCA levels.

There is a 50% chance of SCA level northeast winds developing
across the San Pedro Channel out to Catalina Island tonight into
Saturday. A Marine Weather Statement remains in effect to address
possible effects for the front side of Catalina Island.

&&

.FIRE WEATHER...18/342 PM.

Weak offshore winds continue this afternoon across the mountains
and valleys of Los Angeles counties, with gusts generally in the
20 to 35 mph range. Humidity levels remain quite low this
afternoon away from the coast with minimums of 10 to 20 percent.
As a result, elevated to brief critical fire weather conditions
will continue this afternoon, mainly for the mountains and
breezier valleys of Los Angeles and Ventura Counties.

Another moderate to locally strong Santa Ana wind event is
expected for tonight through early Sunday. Winds will quickly
ramp up this evening, then peak overnight through early Saturday
afternoon. Gradients and upper-level support are forecast to be
slightly weaker than the past event. As a result, peak winds will
likely be weaker with coasts and valleys gusting 30 to 50 mph
(with local gusts to 60 mph in the foothills) and mountains
gusting 40 to 60 mph (with local gusts to 70 mph for favored peaks
and canyons). Humidity levels will initially start out above
critical levels at the onset of stronger winds this evening, but
will lower by early Saturday morning in the 12 to 20 percent
range. Winds will slowly diminish by Saturday night and Sunday
morning, but will remain gusty in the mountains and wind prone
valleys of Los Angeles and Ventura counties during this time, with
gusts in the 30 to 45 mph range. Humidity levels will likely be
even lower Saturday night into Sunday across the mountains and
wind prone valleys of Los Angeles and Ventura counties, with 8 to
15 percent readings becoming common, resulting in critical red
flag conditions likely continuing into Sunday morning for these
areas. There is increased confidence that there will be widespread
6+ hours of critical fire weather conditions for wind prone areas
of Los Angeles and Ventura counties with this event, resulting in
the Red Flag Warning issuance.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 3 PM PST Saturday for zones
      53-354-355-358-362-547. (See LAXNPWLOX).
     High Wind Warning in effect until 3 PM PST Saturday for zones
      54-88-359-363. (See LAXNPWLOX).
     Red Flag Warning in effect until 10 AM PST Sunday for zones
      254-288-358-359-363-547. (See LAXRFWLOX).
     Red Flag Warning in effect until 10 PM PST Saturday for zones
      354-355-362. (See LAXRFWLOX).
PZ...Gale Warning in effect until 2 PM PST Saturday for zones
      650-655. (See LAXMWWLOX).
     Small Craft Advisory in effect until 2 PM PST Saturday for
      zone 676. (See LAXMWWLOX).

&&

PUBLIC...Hall/Thompson
AVIATION...DB
MARINE...Sirard
FIRE...Gomberg
SYNOPSIS...Hall

weather.gov/losangeles

Experimental Graphical Hazardous Weather Outlook at:
https://www.weather.gov/erh/ghwo?wfo=lox