High Wind in California, January 28, 2022

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1014 PM PST Thu Jan 27 2022

.SYNOPSIS...27/218 PM.

Gusty Santa Ana winds are expected tonight through at least Friday
then weaken through the weekend. A cooling trend is expected next
week as high pressure weakens but no rain is expected.

&&

.SHORT TERM (THU-SUN)...27/749 PM.

***UPDATE***

The LAX-DAG pressure gradient was -4.0 mb at 03Z and is forecast
by the latest NAM to fall to -8.3 mb at 12Z late tonight. Offshore
flow was already in place this evening for the VTU/L.A. County
mtns and many vlys, with gusts of 35 to 45 mph in the windier mtns
and foothills. With the strong offshore gradients and some
thermal support, conditions are on track for these winds to
increase further overnight and spread to the lower vlys and some
coastal areas. Wind Advisories are in affect for much of VTU/L.A.
Counties tonight into Fri, with gusts in the 40 to 55 mph range
expected, strongest in the mtns, including the Santa Monica Mtns.
Please see the latest Non-Precipitation Weather Message
(LAXNPWLOX) for further details.

Mostly clear skies this evening will continue overnight, with
just a few high clouds from time to time. A dry airmass over the
region will help to promote good radiational cooling in the
sheltered areas. This will lead to freezes in the SLO County
interior vlys and Antelope Vly, with patchy frost in other
sheltered areas such as the Santa Ynez Vly and the Ojai Vly.

***From Previous Discussion***

A cold surface high pressure area will build tonight over the
intermountain west. As this happens, offshore surface pressure
gradients from the northeast will strengthen and Santa Ana winds
will pick back up. By early Friday morning, the 12Z run of the NAM
forecasts the LAX-DAG gradient to peak around -9 mb. Typically
the NAM runs about 2 mb too strong, so the gradient would likely
verify closer to -7 mb. The 12Z runs of the GFS and ECMWF are in
similar agreement though slightly weaker with the gradient peaking
around -5 or -6 mb. In addition to a decent gradient to kick up
winds, there will also be a lot of cold advection as a tight
thermal gradient will form as cold air banks up along the north
side of the mountains. This will increase subsidence and give
momentum to the wind to reach the coastal areas from Ventura to
Malibu and even over the inner coastal waters by the overnight to
early morning hours. An important item of note for this Santa Ana
wind event is that the flow aloft is more easterly with not much
push from the north. What does this mean for the actual wind
event? This will open the door for more wind to flow through
Ventura County. To put that in perspective, the wind event from
last weekend that had a more northerly push had a greater impact
through LA County. The axis of strongest winds for this event
(aside from ridgetops) will likely run from the Santa Clarita
Valley westward towards Ventura. Wind Advisories will go into
effect at 7pm for the LA and Ventura County mountains, wind-prone
valleys (this does NOT include Antelope Valley or San Gabriel
Valley), and coastal areas (from Ventura to the Hollywood Hills).
They will last through Friday afternoon with the strongest winds
expected in the morning. Upper-level support and cold advection
die off Friday afternoon, but high-resolution guidance indicates
breezy to gusty winds lasting through Saturday morning. Therefore
may need to extend the advisories, but will wait until tomorrow to
make that call.

Thanks to cold advection, overnight low temperatures are expected
to be quite cold across the interior and over wind-sheltered
areas (e.g., Ojai). The Antelope Valley will be the coldest, with
temperatures in the upper teens to low 20s expected again. Other
cold areas will range from the upper 20s to mid 30s. With
temperatures this cold it will be critical to make sure all pets
are brought inside. High temperatures on Friday will be a battle
between cold advection and downslope warming. I'm thinking the
cold advection will win out especially through the main wind
corridor so temperatures will max out 3 to 6 degrees cooler than
today. Saturday will start out as another very chilly morning but
not quite as cold as Friday. Despite less cold advection, heights
will lower from an upper-level low moving through with a grip of
clouds so highs on Saturday will likely cool further, except the
interior. A small ridge develops on Sunday and the entire area
will warm, especially over the interior.

.LONG TERM (MON-THU)...27/216 PM.

The extended period of the forecast will be marked by a longwave
trough extending across the western two-thirds of the CONUS. There
are some differences between how the GFS and ECMWF operational
runs handle the evolution of the pattern. The GFS shows a couple
impulses moving through the flow from the north on Tuesday into
Wednesday and again on Thursday. With the ECMWF at a lower
resolution, these features are not as defined. Along with their
slew of ensemble members, both models (as well as the Canadian and
its ensemble members) agree that the future looks dry.

The main weather highlights for this period are some cooling each
day as well as a potential for more wind. Temperatures will
return back to below seasonal norms by mid-week. High temperatures
will be in the 60s near the coast and upper 50s inland. Offshore
pressure gradients strengthen on Wednesday as an inside slider is
expected to move through. There is a lot of spread in the EPS
members so the wind forecast is very low confidence for now, but
there is a chance of another round of gusty offshore winds.

&&

.AVIATION...28/0606Z.

At 0500Z at KLAX, there was no marine layer. There was a sfc based
inversion with a top of 1000 feet and a temp of 18 C.

High confidence in 00Z VFR TAFs, moderate confidence in winds.
Timing of wind changes could be off by +/- 2 hours and off by +/-
5 kt. N to NE winds may produce moderate to strong LLWS and UDDFS
in and around L.A. and Ventura County mountains and foothills.

KLAX...High confidence in VFR TAF. There is a 20% chance of an
6 kt east wind component from 12Z-20Z. Otherwise, high confidence
in any east wind component remaining below 4 kt.

KBUR...High confidence in CAVU TAF.

&&

.MARINE...27/735 PM.

For the outer waters, Small Craft Advisory (SCA) level NE winds
are expected south of Pt. Conception to San Nicolas Island late
tonight through Friday morning. There is a 40% chance of SCA level
NW winds Sunday and Monday. Otherwise, winds and seas are
expected to stay below SCA levels.

For the inner waters N of Pt. Sal, winds and seas are expected to
remain below SCA levels through the period.

For the inner waters S of Pt. Conception, SCA level NE winds are
expected from Ventura to Malibu and out to Anacapa/Santa Cruz
Islands tonight and into the afternoon Friday. There is a 40%
chance these winds could continue into the evening. Otherwise, SCA
conditions are not expected through the period.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 4 PM PST Friday for zones
      40-41-44>46-53-54-88-547. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 PM PST Friday for
      zones 650-655. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 AM to 3 PM PST Friday
      for zones 673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (SUN-THU).

There is a chance of gusty northerly winds by the middle of next
week.

&&

PUBLIC...Stewart
AVIATION...Rorke
MARINE...Lund
SYNOPSIS...Stewart

weather.gov/losangeles

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