Wind Advisory 81, NWS Los Angeles, CA

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1252 PM PDT Sun Jun 12 2022

.SYNOPSIS...12/447 AM.

An area of low pressure moving through the Pacific Northwest will
bring a cooling trend to the region through Monday as onshore flow
strengthens and deepens the marine layer depth. Gusty northwest
to north winds are expected Sunday and Monday, strongest Monday
night. Another warming trend is expected Tuesday through Thursday
as high pressure aloft builds into the West Coast. A significant
cool down is possible next weekend.

&&

.SHORT TERM (TDY-TUE)...12/1013 AM.

***UPDATE***

Current satellite imagery shows a solid deck of marine layer
clouds covering most of the coastal waters and extends over the
beaches, through the plains and into the valleys. The marine layer
varies in depth from 1600 feet at LAX to around 500 feet north of
Point Conception, and quite a few areas experienced dense fog
overnight along the Santa Barbara County Coasts. Clouds and fog
are burning off rapidly over the southern valleys and Central
Coast valleys this morning, but expecting clouds/fog to linger at
portions of the coasts today, especially for the Ventura County
Coast with moderate onshore flow and a current LAX-DAG onshore
pressure gradient of 5.6 mb.

Upper level flow today continues from the northwest, but
strengthens as an upper level trough approaches. Falling heights
yield 6-10 degrees of cooling for interior areas and portions of
the valleys. High temperatures in coastal regions should be nearly
the same as Saturday. May consider cooling the Santa Barbara south
coast, but with warm Sundowner winds expected this
evening/tonight, high temperatures may occur late. Current wind
advisories for these Sundowner winds look on track, starting at
4PM this evening.

An upper level trough passes through the region tonight into early
Monday morning which may disrupt the marine layer pattern shifting
clouds and fog to favor the Central Coast and LA County. The
trough also brings a slight chance for light drizzle, with no
significant accumulations expected.

Monday, temperatures continue their downward trend with the
warmest spots only reaching the 80s. However, southern coastal
areas should see a few degrees of warming and Santa Barbara south
coast trends 5-9 degrees warmer due to the lack of marine layer
clouds and plenty of Sundowner winds. The more impactful weather
Monday comes from a strong northerly push bringing strong winds
from the Santa Barbara South Coast to the interior Santa Barbara
County mountains through Ventura and LA County mountains to the
deserts. There is the potential for winds to reach gusts to 60
mph but confidence is lower due to the current lack of agreement
between model runs. Will likely require wind advisories earlier
Monday for the Antelope Valley, and southern mountain areas leading
up to the High Wind Watch.

Minor edits were made to this afternoon's cloud grids, but
otherwise the forecast looked on track with no significant
changes.

***From Previous Discussion***

The latest fog product imagery shows the marine layer induced low
clouds and fog becoming well entrenched over the coastal waters
and into the coast and valley areas this morning. Onshore flow
continues to strengthen as high pressure aloft flattens while an
upper-level trough of low pressure approaches the Pacific
Northwest. This trough, located about 350 miles west-northwest of
Crescent City, will split the ridge pushing the western ridge back
to the southwest and the eastern edge back into Texas by Monday. A
cooling trend will establish today and linger through the weekend
and into Monday.

Night through morning low clouds and fog will become a staple of
the forecast for most coastal and valley areas. The land mass
will struggle to clear again this afternoon as the air mass
moistens up ahead a dying frontal boundary over the North Coast of
California. The marine layer depth will deepen into tonight as the
boundary moves south down the state through this evening. 850 mb
mixing ratios increase to near 10-11 g/kg, or about five standard
deviations above the mean. Some concern remains for the possibility
of light showers or heavy measurable drizzle along the immediate
Central Coast portions tonight as the air mass is rather moist.
PoPs have been increased and a slight chance of showers or
measurable drizzle has been added for areas around Point Arguello
along the Santa Barbara County portion of the Central Coast.

Besides the cooling, the main story seems to be the developing
northerly wind event. A tight northerly pressure gradient will
develop as the boundary passes and in the wake of the boundary as
cold air advection will spread in behind it. Wind advisories have
been added for southern Santa Barbara County starting this
afternoon and continuing into Tuesday morning. A wind advisory may
be needed for the Interstate 5 Corridor from late tonight through
Monday morning. As the northerly gradient tightens on Monday and
Monday night, a high wind watch was added for the Santa Ynez Range
and the southwestern portion of Santa Barbara County as NAM-WRF
solutions continue to indicate KSBA-KSMX surface pressure gradient
tightening to around -5 mb and NAM BUFR time height show a 40
knots wind core just off the surface at Gaviota. A high wind watch
was also added for the Interstate 5 Corridor for Monday night and
into Tuesday morning as NAM-WRF solutions indicate boundary layer
winds approaching 30-40 knots and 850 mb winds approaching 45
knots. a wider swath of wind advisories may be needed on Monday
for much of the Central Coast and the Santa Ynez Valley and into
the Santa Clarita and Antelope Valleys in Los Angeles County as
the gradient is strong on Monday.

Cold air advection behind the boundary will scour the marine
layer clouds and could wipe out the low cloud field between Monday
and Tuesday. Higher resolution model solutions suggest the low
cloud field consolidating along the Orange County beaches and
remaining intact, then advancing north slowly through the weekend
as the northerly surface gradient weakens.

The cooling will bottom out on Monday, then ridging aloft will
build back in from the west. Ridging aloft will nose in from the
west and the air mass will start to warm for Tuesday. Northerly
winds could linger some into Tuesday, especially through the
Interstate 5 Corridor and across southern Santa Barbara County.
Almost all members of the EPS, GEFS, and CMC model ensembles
suggest a warming trend taking shape on Tuesday.

.LONG TERM (WED-SAT)...12/1251 PM.

Moderate to high confidence in the long-term forecast as
deterministic models are in good agreement, especially for
Wednesday and Thursday. Wednesday, the overall pattern of
persistent northwest flow becomes weak in the lull between
northern pacific low pressure systems and as high pressure is the
dominate feature. However, this should be short- lived as the
ECMWF and GFS agree on another deep cutoff low drops into the
waters northwest of California. This low system is forecast to dig
south, driving southwest Thursday into Friday. However, there is
lower confidence starting Thursday as the models disagree on how
far south the system initially pushes. Heights fall Friday as the
system passes through, and overall flow shifts more northerly.

Temperatures peak Wednesday and Thursday over interior areas, yet
stronger onshore flow Thursday should limit heating at the
coasts. The approaching low helps drive strong onshore flow and
this combined with falling heights leads to a cooling trend into
Saturday. Marine layer clouds will be somewhat limited Wednesday
to Thursday morning, but the nearing low will allow the marine
layer to expand and deepen for Friday and Saturday.

&&

.AVIATION...12/1823Z.

At 1728Z at KLAX, the marine layer was near 1500 ft deep. The top
of the inversion was near 4700 ft with a temperature of 24 C.

Low clouds and fog have cleared back to the coast and most all the
TAF sites are VFR, except KSBA and KOXR. The marine clouds are
poised right at the coastand could occasionally push into anyv
coastal site this afternoon with brief IFR/MVFR conditions. Expect
an early return of the low clouds to most coastal areas again
this evening. Clouds will affect the coastal plain tonight, and
likely (50 to 60 percent chance) penetrate farther into the
valleys as the marine layer should be slightly deeper. Conditions
should be mostly IFR to MVFR with a deeper marine layer, although
brief LIFR conditions are possible in the valleys.

KLAX...Moderate confidence in TAF. There is a 30 percent chance of
marine clouds arriving plus or minus two hours from the forecasted
time. East winds are expected to remain below 8 kt, but there is a
20 percent chance of brief periods of 8 kt or more.

KBUR...Moderate confidence in TAF. There is a 20 percent chance of
VFR conditions through the period.

&&

.MARINE...12/917 AM.

No changes to the marine forecast in the morning update.

Small Craft Advisory (SCA) level NW winds continued in zone
(PZZ670) and far NW portions of zone PZZ673. SCA level winds will
overspread the remainder of zone PZZ673 and PZZ676 today. Winds
are expected to increase to Gale force across northern areas late
this afternoon, and by late tonight in the central zone. SCA level
winds will continue across southern areas thru early Mon
afternoon, but there is a good chance (50%) they will reach Gale
force Mon afternoon. Gale force winds are likely to continue thru
at least late Tue night, with SCA conds Wed thru Thu. There is a
40-50% chance of Gales continuing Wed/Thu, especially across
northern sections.

Strong winds will create large, choppy seas thru the outer waters
tonight thru Tue. Wave heights should reach 10 ft by late Sun
night/Mon morning, then increase a bit more thru Mon night. Steep
waves with gusty winds will create dangerous sea conditions for
boaters, especially for small vessels.

For the inner waters N of Pt. Sal, SCA level NW winds are
expected this afternoon thru late this evening. Even though winds
will likely drop off tonight/Mon morning, seas should remain at
SCA levels. SCA level winds are likely during the afternoon and
evening hours Mon thru Thu, and there is a 40-50% chance of Gales
Mon afternoon/evening. Even when winds drop below SCA levels each
night/morning, steep, choppy seas may remain high enough to
maintain SCA conds right thru Thu, with only minor respites.

For the inner waters S of Pt Conception, SCA level W-NW winds are
expected in the western SBA Channel during the afternoon thru late
night hours today thru Thu, with conditions close to SCA levels
across the remainder of the channel. There is a 40% chance of SCA
level W-NW winds across western portions of the southern inner
waters during the afternoon/evening hours today thru Mon.

&&

.BEACHES...12/1251 PM.

High astronomical tides expected with the full moon on Tuesday are
expected to exceed 7 feet, approaching 7.3 to 7.4 feet in some
places, from Monday evening through Wednesday evening. The high
tides will cause the possibility of minor tidal overflow around
the time of high tide, inundating more exposed parking lots with
some minor flooding. No structures are expected to be affected.

In addition, strong winds in the coastal waters over the next few
days will generate elevated surf in mainly west and northwest
facing beaches. The elevated surf is expected to generate a high
risk of rip currents, mainly Monday and Tuesday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Wind Watch in effect from Monday evening through Tuesday
      morning for zones 53-54. (See LAXNPWLOX).
     Wind Advisory in effect from 4 PM this afternoon to 9 AM PDT
      Monday for zones 349-351. (See LAXNPWLOX).
     High Wind Watch in effect from Monday afternoon through
      Tuesday morning for zones 349-351-352. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 PM PDT Monday for
      zones 645-676. (See LAXMWWLOX).
     Gale Watch in effect from Monday afternoon through late
      Monday night for zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Monday for
      zones 650-673. (See LAXMWWLOX).
     Small Craft Advisory in effect until 6 PM PDT this evening
      for zone 670. (See LAXMWWLOX).
     Gale Warning in effect from 6 PM this evening to 3 AM PDT
      Wednesday for zone 670. (See LAXMWWLOX).
     Gale Warning in effect from 3 AM Monday to 3 AM PDT Wednesday
      for zone 673. (See LAXMWWLOX).
     Gale Watch in effect from Monday afternoon through late
      Tuesday night for zone 676. (See LAXMWWLOX).

&&

PUBLIC...Phillips/Hall
AVIATION...Sweet/DB
MARINE...Sweet/DB
BEACHES...Sweet
SYNOPSIS...Hall

weather.gov/losangeles

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