High Wind in California, April 9 to 10, 2021

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1149 PM PDT Thu Apr 8 2021

.SYNOPSIS...08/838 PM.

There will be gusty winds across the region through late Saturday,
with particularly strong evening winds in southern Santa Barbara
County. Overnight and morning low clouds and fog will form north
of Point Conception into Friday, then will be widespread through
the week. Warm temperatures turn cooler from Sunday into next week.

&&

.SHORT TERM (THU-SUN)...08/756 PM.

***UPDATE***

High pressure west of the Pacific Northwest, along with lower
pressure over the Southern California Bight, has maintained
moderate to strong northerly surface pressure gradients across the
area. The strongest gradients, and strongest north winds, are
occurring over southern Santa Barbara County, including the Santa
Ynez Range and the western South Coast. A High Wind Warning in
this area will be in effect through 9 AM Saturday with gusts
between 50 to 60 mph expected. Later tonight as gradients shift
to slightly east of north, some gusty winds will likely develop in
the foothills above Montecito as well.

Gusty northwest to north winds over the LA and Ventura Mountains,
and Santa Clarita Valley will persist through 6 AM Friday, with
W-NW winds in the Antelope Valley beginning to diminish late this
evening and overnight.

The sky cover forecast is tricky once again, and the area most
likely to see low clouds is the Central Coast, especially the
Santa Barbara section. Much lower certainty is the LA Basin, where
skies have remained mostly clear on previous nights. While models
hint at some low cloud coverage there, the best likelihood is for
a few hours of broken clouds at Long Beach and possibly LAX, with
otherwise clear conditions.

***From Previous Discussion***

Upper level ridging will be along and off the CA coast through
Sun. Some low clouds can be expected along the Central Coast,
Santa Ynez Vly and Salinas Valley each night and morning tonight
thru Sat, then just along the SBA Central Coast Sat night into Sun
morning. There should also be some low clouds and fog along the
L.A. County coast each night and morning, possibly extending into
the San Gabriel Vly, thanks an eddy over the SoCal Bight each
night. Otherwise, mostly clear skies will prevail tonight thru
Sun. Temps will continue to be several degrees above normal away
from the coast thru Sun despite a slow cooling trend. The warmest
vlys and lower mtns will be in the upper 70s to mid 80s Fri, mid
70s to low 80s Sat, and 70s to near 80 Sun.

Strong northerly gradients will continue at least thru Sat,
strongest over SBA County. This along with continued upper level
support will result in strong and gusty winds across the SBA
County mtns and S coast, where Warning-level gusts up to 60 mph at
times will be possible tonight through Saturday morning,
including the Montecito Hills. There will also continue to be
Advisory- level gusts for the L.A./VTU County mtns and the Santa
Clarita Vly thru late tonight. Another round of gusty Advisory-
level winds will be possible in these areas Fri night into Sat
morning as well. Otherwise, gusty mainly sub-Advisory level W-N
winds can be expected at times thru Sat, strongest along the
Central Coast, as well as in the Santa Monica Mtns and some of the
vlys of VTU/L.A. Counties.

.LONG TERM (MON-THU)...08/226 PM.

The GFS and EC are in generally good agreement thru the extended
period. An upper level trof will approach the area from the N on
Mon with lowering H5 heights. An upper level low is forecast to
develop over the central Great Basin Tue and linger there thru
Wed with a sharper upper level trof extending into central CA. The
upper level trof will then linger over the region into Thu.

This system will deepen the marine layer quite a bit especially
into mid week when marine layer clouds could move into the coastal
slopes over VTU/L.A. Counties. Most of the low clouds will affect
the region night and morning hours, but with moist onshore flow,
lingering clouds cannot be ruled out thru the afternoon in some
areas especially Wed and Thu. There is also an outside chance that
drizzle or light rain could affect the coast, vlys and coastal
slopes of VTU/L.A. Counties Tue night into Wed and possibly Wed
night and Thu. Good onshore flow will prevail thru the extended
period as well, along with cooler temperatures especially for the
coast and vlys. By Wed, the coast and vlys should be 2-8 deg below
seasonal norms, with highs generally in the 60s to low 70s.

&&

.AVIATION...09/0648Z.

At 0515z at KLAX...the marine layer was around 800 feet deep. The
top of the inversion was around 2200 feet with a temperature of 20
C.

Moderate confidence in coastal TAFs through 17Z where there is a
30 percent chc of IFR cigs at sites with no cigs fcst and the same
30 percent chc of no cigs at sites with cigs fcst. Good confidence
in TAFS after 17Z.

Good confidence in inland TAFs.

KLAX...Moderate confidence in TAF through 17Z. There is a 30
percent chc of no low clouds at the terminal. Good confidence in
TAF 17Z-07Z then lower confidence due to timing of arrival of IFR
cigs. Any east wind component will be 5 kt or less.

KBUR...Very good confidence in VFR fcst.

&&

.MARINE...08/924 PM.

Patchy overnight and morning fog, locally dense with visibility
under one mile, will continue through the week.

Across the outer waters... Winds will be Gale force level through
Saturday, then Small Craft Advisory (SCA) level Sunday through
Tuesday. Winds will be weaker during the morning hours. Seas will
be SCA level Friday through Sunday.

Across the nearshore waters of the Central Coast... Winds will be
SCA level mostly in the afternoon and evening hours through
Monday, then diminish to below SCA level on Tuesday. Seas will be
SCA level Saturday and Sunday.

Across the inner waters south of Point Conception... Winds will
be SCA level this evening and continue through Tuesday from Point
Conception to Santa Barbara and to Monday elsewhere. Winds will
diminish to below SCA level during the morning hours. There is a
thirty five percent chance of wind gusts reaching Gale force
Friday afternoon and evening in the western portion of the Santa
Barbara Channel. Otherwise, conditions will be below SCA level.

The stronger wind gusts will produce steep, short-period
hazardous wind waves across the waters.

&&

.FIRE WEATHER...08/233 PM.

A persistent northerly pressure gradient and rather dry air will
remain over the fire district through the upcoming weekend. Where
fuels are driest and especially on southern exposures, there could
be areas of the Santa Barbara, Ventura, and Los Angeles County
foothills and mountains that are more receptive to small fire
spread due to the combination of gusty winds and low minimum
humidities. However, no Red Flag Warnings will be issued due to
relatively high fuel moisture conditions across the fire
district. 

Peak wind gusts of 50-60 mph will be common across interior and
southern Santa Barbara County through Saturday morning, along with
gusts of 40-50 mph through the I-5 corridor and into the Santa
Clarita Valley and northern foothills of the San Fernando Valley.
Humidities in the foothill and mountain regions will drop to
minimums of 6-15 percent on Friday and Saturday with only slight
improvement on Sunday afternoon. Poor overnight recoveries of
15-30 percent will occur in these areas where winds remain a
factor. The central and south coasts will continue to be cool and
somewhat humid with night and morning low clouds and patchy fog.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Wind Warning in effect until 9 AM PDT Saturday for zones
      39-52. (See LAXNPWLOX).
     Wind Advisory in effect until 6 AM PDT Friday for zones
      53-54-88. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Saturday for
      zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Friday for
      zones 650-655. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 PM Friday to 3 AM PDT
      Saturday for zones 650-655. (See LAXMWWLOX).
     Gale Warning in effect until 3 AM PDT Sunday for zones
      670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (SUN-THU).

Gusty north winds will continue Saturday night and Sunday,
focused over Santa Barbara County and Los Angeles County,
including some valleys and coasts as well as the coastal waters.
Expect hazardous driving and boating conditions, possibly downed
trees and power outages, as well as damage to portable shelters.
Gusty west winds are possible over interior areas early to middle
of next week.

&&

PUBLIC...Sirard/Smith
AVIATION...Rorke
MARINE...Kj
FIRE...Boldt
SYNOPSIS...Kj

weather.gov/losangeles