High Wind in California, March 27 to 28, 2022

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
849 PM PDT Sun Mar 27 2022

.SYNOPSIS...27/746 PM.

A storm will move over the region late tonight through early
Tuesday, bringing widespread rain, high elevation snow, and gusty
winds. There will be a slight chance of thunderstorms that could
produce heavy downpours and small hail late Monday morning through
Monday night. Drier conditions are expected the remainder of the
week with near normal temperatures.

&&

.SHORT TERM (SUN-WED)...27/848 PM.

Much awaited storm system moving into Northern and Central
California this evening with leading edge of main rain band
pushing into the Big Sur area as of 8 pm. In advance of the main
rain band associated with the cold front, there will be increasing
pre-frontal rainfall associated with a developing warm front this
evening, especially across south and southwest facing slopes
where orographic enhancement will be increasing. Automated rain
gauges already showing light rainfall developing across the
Santa Ynez range in the past couple of hours.

Storm remains generally on track in regards to overall rain/snow
amounts and winds, with just a few adjustments with the evening
update. Models show two distinct impulses coming through the
region over the next 24 hours. The first one being associaated
with the cold front producing a 3-6 hour period of moderate to
heavy rainfall across San Luis Obispo and Santa Barbara counties
between midnight and 8 am, then across Ventura and LA counties
between 6 am and 1 pm Monday. This system will tap into a moist
atmospheric river plume with IVT values as high as 500 kg/m/s off
the Central Coast and precipatable water values up to 1 inch.
There will also be strong upslope orographic enhancement with
this first impluse, with 850-700 mb southerly winds of 40-50
knots which will generate significantly enhanced rainfall
amounts and intensities across our transverse mountain ranges.
Lastly there will also be strong jet dynamics associated with
a 130 knot jet core off our coast. With the factors
mentioned above, still looking for peak rainfall rates to
generally range between 0.40 and 0.75 inches per hour (highest
across south facing slopes). However, isolated rates as high
as 0.75 to 1.00 inch per hour are becoming more likely across the
most favored south facing slopes between 6 am and noon, including
the eastern half of the Santa Ynez Range, Topa Topa mountains in
Ventura county, and the eastern San Gabriels (including the Bobcat
burn area). These areas will have the combination of strongest
upslope orographic flow and optimal jet dynamics. Will continue
to hold off on a Flood Watch for the recent burn areas, as the
threat of significant debris flows looks minimal for these areas,
however, there could be some minor mud and debris flows in the
Alisal and Bobcat burn scars.

A second and more convective impulse will follow a few hours
later. This second impulse will not be as organized or widespread
as the initial frontal band but given that we're already seeing
several lightning strikes around the cold core low it's likely
we'll see similar peak rain rates as it moves through the area.
Though durations will be shorter given the more convective nature.
There is an increasing chance of thunderstorms with this second
wave, starting as early as Monday morning across San Luis Obispo,
Santa Barbara, and Ventura counties, then extending into LA county
by Monday afternoon. The convective threat will continue into
at least Monday evening. The convective parameters associated with
this second wave are favorable for thunderstorms include cold air
advection aloft (500 mb temperatures falling to between -23 and
-25 degrees Celsius, lifted index values between -2 and -5, and
surface based CAPE values between 300-700 J/kg). There is the
potential for a few of these thunderstorms to be strong, producing
brief heavy downpours capable of roadway flooding, accumulating
small hail, and strong wind gusts. The threat of thunderstorms
will also bring impacts to the beaches due to the threat of cloud
to ground lightning. And lastly, there is some low level directional
shear and jet dynamics that will bring the threat of isolated
waterspouts across the coastal waters.

This system will also pack strong winds across many portons of
the forecast areas, especially the mountains, interior valleys,
Central Coast, and Antelope Valley where wind advisories
are already in effect for widespread wind gusts between 40 and
55 mph. The higher mountains of LA/Ventura counties will likely
see the strongest south-southwest winds with this system where
gusts up to 65 mph are expected. A winter storm warning is already
in effect for these areas. Localized  damaging wind gusts up to
60 mph are also possible across the foothills of the Antelope
Valley as mountain wave conditions could develop. A wind advisory
may need to be added for coastal areas south of Point Conception
as gusts up to 35 mph will be possible.

*** From previous discussion ***

Snow levels will be above the major highways, mostly at or above
6000-7000 feet. However, significant snow accumulations are
expected above those levels and the winter storm watch has been
converted to a warning for later tonight through Monday night.

Showers and storms expected to taper off Monday evening and by
early Tuesday precip should mostly be east of the area, though
some lingering north slope showers (snow level above 5000 feet)
are possible near the Grapevine area.

Dry weather expected the rest of Tuesday and Wednesday, though
gusty north winds at times, especially in the mountains and across
southern Santa Barbara County. Temperatures remaining a little
below normal.

.LONG TERM (THU-SUN)...27/218 PM.

No significant weather issues expected mid to late week. Most of
the EC ensembles continue to suggest some very light precip on
Thursday but this does not jive with the upper level pattern or
any of the GFS ensembles. Will leave it in the official forecast
but have very little confidence that any precip will fall
Thursday. Otherwise, a pretty quiet pattern with light to moderate
onshore flow to the east and very minimal gradient from the north
after Wednesday so with the exception of typical breezy Antelope
Valley afternoons winds should be on the light side. Some warming
expected late in the week going into the weekend as weak high
pressure develops.

&&

.AVIATION...28/0015Z.

At 0005Z at KLAX, the marine layer was around 2500 ft deep. The
top of the inversion was around 4000 ft with a temperature of 13
C.

Low to moderate confidence in all TAFs. Timing of rain changes
could be off by 2 hours. Visibilities 1-3 SM likely in heavier
rain as cold front pushes through the region Monday morning. Cigs
could bounce between MVFR-IFR during rain. Behind cold front,
a cold and unstable air mass will bring a 20 percent chance
of thunderstorms across all TAF sites after 18z Monday.

KLAX...Low to moderate confidence in the 00Z TAF. Cigs could
bounce between MVFR-IFR during rain Monday morning. Southeast
winds could exceed 10 knots between 06z-12z. As cold front
approaches, winds becoming more east-southeast and strengthen
between 13-20z Monday, with gusts in the 20-30 knot range.
Winds becoming south-southwest and remaining gusty after 21z.
There is a 20 percent chance of thunderstorms after 20z.

KBUR...Moderate confidence in the 00Z. Cigs could
bounce between MVFR-IFR during rain Monday morning. Southeast
winds could exceed 10 knots between 06z-12z. As cold front
approaches, southeast winds increase between 13-20z Monday, with
gusts in the 20-30 knot range. There is a 20 percent chance of
thunderstorms after 20z.

&&

.MARINE...27/746 PM.

For the Outer Waters, moderate confidence in forecast. SE-S gale
force winds are expected in the northern two zones thru late
tonight. Across the southern zones, Small Craft Advisory (SCA)
level SE-S winds are expected, with a 20-30% chance of Gale Force
gusts later tonight. SCA level winds are expected across the
entire outer waters Mon morning, with seas likely lingering in the
SCA category thru Mon night. Then winds are expected to switch
around to the NW Mon afternoon, dropping below SCA briefly but
increasing to SCA level again Mon night thru Thu. Gale Force winds
are possible Tue afternoon into Thu.

For the Inner Waters N of Pt Sal, moderate confidence in forecast.
SE-S winds should increase to Gale force this evening, but this
may hold off until late evening. Gales are expected to decrease
to SCA level S-SW winds late tonight, then SCA conds will persist
Mon morning. There may be a brief respite from SCA conds Mon
evening into Tue morning, then SCA level NW winds are expected
for much of the time Tue afternoon thru Thu. There is a 20% chance
of Gale force winds Wed afternoon thru Thu.

For the SBA Channel, SCA level E-SE winds are expected to overspread
the SBA Channel this evening and tonight. There is a chance of
brief Gale Force gusts late tonight into early Mon. Winds will
shift to SW and decrease below SCA levels Mon afternoon. SCA level
W-NW winds are expected Tue morning thru the evening and again
during the afternoon and evening hours on Wed.

For the Inner Waters S of Pt Mugu, SE-S winds are expected to reach
SCA levels late this evening, then continue through early Mon
afternoon before turning SW and decreasing below SCA levels. There
is a 20% chance of winds remaining at SCA levels until late Tue
night. Then, SCA level W-NW winds are expected during the
afternoon/evening hours Tue, with a 30% chance during the
afternoon/evening hours Wed and Thu.

There is a slight chance of thunderstorms across all the coastal
waters Monday and Monday night. Brief heavy rain, gusty winds,
small hail, and even waterspouts will be possible.

&&

.BEACHES...27/758 PM.

Elevated to high surf is expected for most beach areas Monday
through Monday night. A moderate period west swell (12-14
seconds) moving into the waters will peak Monday afternoon and
evening. At the same time, moderate to strong southerly winds
ahead of an approaching frontal system will result in rapidly
building, short period southerly waves. The combination will
create large, rough seas affecting much of the coastline during
this time. The elevated to high surf may continue into Tuesday
morning.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 3 PM PDT Monday for zones
      34>39. (See LAXNPWLOX).
     High Surf Advisory in effect from 3 PM Monday to 3 AM PDT
      Tuesday for zones 34-35-40. (See LAXCFWLOX).
     Beach Hazards Statement in effect from Monday afternoon
      through late Monday night for zones 39-41-87. (See LAXCFWLOX).
     Wind Advisory in effect from 5 AM to 10 PM PDT Monday for
      zones 46-88. (See LAXNPWLOX).
     Wind Advisory in effect until 6 PM PDT Monday for zones
      51-52. (See LAXNPWLOX).
     Wind Advisory in effect until 10 PM PDT this evening for
      zones 53-54. (See LAXNPWLOX).
     Winter Storm Warning in effect until 6 AM PDT Tuesday for
      zones 53-54. (See LAXWSWLOX).
     Wind Advisory in effect until 10 PM PDT Monday for zone 59. (See LAXNPWLOX).
PZ...Gale Warning in effect until 3 AM PDT Monday for zones
      645-670-673. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 PM PDT Monday for
      zones 650-655. (See LAXMWWLOX).
     Small Craft Advisory in effect until 9 PM PDT Monday for zone
      676. (See LAXMWWLOX).

&&

PUBLIC...Gomberg/MW
AVIATION...Gomberg
MARINE...DB/Lund/Smith
BEACHES...Smith
SYNOPSIS...MW/Smith

weather.gov/losangeles

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