LA Area Forecast Discussion

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FXUS66 KLOX 030542
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1042 PM PDT Sat Jul 2 2022

.SYNOPSIS...02/157 PM.

Coast and valley low clouds and fog will persist during the night
and morning hours through about the middle of next week.
Otherwise, mostly clear skies will prevail along with breezy
onshore flow and below normal temperatures. A significant warm up
is possible late next week into the weekend.

&&

.SHORT TERM (SAT-TUE)...02/910 PM.

***UPDATE***

Falling 500 mb heights combined with strengthening northwest flow
(a moderate Santa Maria to Santa Barbara gradient of -4.4,
trending -0.6 stronger than this time yesterday) have combined to
support an early return of low clouds to the Central Coast this
evening. The moderate gradient was also supporting wind gusts of
35 to locally 55 mph across typical Sundowner areas of southwest
SBA county. The associated wind advisory (NPWLOX) was updated to
include wording that advisory level Sundowner winds will likely
return Sunday and Monday evenings across the same area. Other
windy areas will once again be the foothills of the Antelope
valley through this evening and again Sunday late
afternoon/evening. The I-5 corridor of the LA/VTA mountains will
also see gusty winds. Isolated advisory level wind gusts to 45 mph
will be possible in these areas. Fortunately relative humidity
values will be elevated for southwest SBA county, limiting fire
danger across that region. However, interior areas will remain dry
leading to elevated fire weather conditions where winds pick up.

A moderate Santa Barbara to San Diego gradient (-2.5) along with
model guidance indicates that a moderate eddy should spin up
tonight leading to increased low cloud and fog coverage across LA
and perhaps portions of VTA county. Have increased cloud coverage
in the forecast accordingly for this area as well as interior SLO
county. Pared back Sunday daytime highs a couple of degrees along
the margin of the marine influence in particular, due to the
expected deeper marine layer than previously forecasted.

***From Previous Discussion***

A broad upper level trof over the E Pac is forecast to gradually
move into CA thru Sun then persist over the region through
Tue. H5 heights over swrn CA are expected to fall from 583-587
dam this afternoon to about 580-584 dam from N to S for Sun into
Independence Day then increase to 584-586 dam on Tue. A broad and
dry SW flow aloft will persist over the fcst area thru the
period.

The marine inversion depth is not expected to change much tonight
thru Tue and should be in the 1500-2000 ft range for the most
part. Low clouds and fog are forecast to affect most of the coast
and some vlys night and morning hours tonight thru Tue. The low
clouds should be somewhat minimal over the SBA County S coast
thanks to northerly canyon winds. Otherwise, mostly clear skies
can be expected across SW CA thru the period.

Temps Sun thru Tue will be several degrees below normal in all
areas, with Sun the coolest day. The warmest vlys are expected to
have highs generally in the 80s, with coastal areas in the 60s and
70s.

The good onshore flow will persist as well, with breezy to gusty
SW-NW winds for many areas, strongest in the deserts. The current
and persistent weather pattern is also ideal for gusty Advisory-
level sundowner winds over the southwestern SBA County coast and
mtns each evening. The 18Z 3km WRF was forecasting wind gusts up
to 50 mph or more in this area each evening through Mon. A Wind
Advisory is in effect for tonight for the western Santa Ynez Mtns
and southwestern SBA County coast, with additional Advisories
likely for these areas over the next few evenings.

.LONG TERM (WED-SAT)...02/151 PM.

The GFS and EC mean ensembles are in good agreement compared to
the deterministic, especially late in the extended period. The
broad upper level trof will continue over CA Wed. The trof will
weaken on Thu as an upper level ridge starts to build into srn CA
from the E. Significant upper level ridging will build into the
area Fri and Sat, with H5 heights increasing to near 593-595 dam
Fri and to near 594-596 dam Sat.

The marine layer pattern will continue Wed with varying amounts
of night and morning low clouds and fog along the coast and into
some of the adjacent vlys. The extent of the low clouds will
decrease Wed night into Thu morning, then the upper level ridge
should lower the marine inversion enough Thu night through Sat
morning to greatly minimize any low cloud development along the
coast. Otherwise, mostly clear skies will prevail thru the
extended period.

Temps are expected to be a little warmer Wed but remain several
degrees below normal across the region. Temps will increase
further to near normal Thu, especially for inland areas, and to
significantly above normal levels away from the coast Fri and Sat,
with the warmest day on Sat. Highs in the warmest vlys should
reach well into the 90s to around 100 on Fri, and into the mid 90s
to near 103 on Sat, with cooler 70s and 80s along the coast.

&&

.AVIATION...03/0541Z.

At 0530Z at KLAX, the marine layer was 1000 feet deep. The top of
the inversion was at 3000 feet with a temperature of 22 C.

High confidence in desert TAFs, Low to moderate confidence in all
other TAFs. Eddy circulation expected to bring in low clouds
late tonight/early Sunday morning for coastal/valley TAF sites
in LA/Ventura counties, however decreased confidence in timing
as satellite showing mostly clear skies as of 05z. TAF sites with
MVFR cigs may lower to IFR, and sites with IFR may only form as
low as MVFR. There is a 30% chance of high IFR-low MVFR cigs AT
KVNY from 13Z-16Z. There is a 20% chance of LIFR conds at KSMX.

KLAX...Low to moderate confidence in TAF. Decreased confidence in
timing of cigs at KLAX as satellite picture showing slow
development of low clouds tonight. There is a 30% chance of going
to IFR category instead of MVFR. An eddy circulation is expected
to develop a SE-E wind component late tonight into mid morning
Sunday, but good confidence that it will remain below 8 knots.

KBUR...Moderate confidence in TAF. 50% chance of brief cigs
008-012 between 13Z-16Z Sunday.

&&

.MARINE...02/855 PM.

Across the outer waters, Small Craft Advisory (SCA) level winds
are expected most of the time thru Wed, strongest during the
afternoon/evening hours. There may be a lull in the winds to
below SCA level late Sun night/Mon morning, and winds may be just
below SCA levels across the northern zone (PZZ670) late Mon night
thru Wed.

Across the inner waters north of Pt. Sal, SCA level winds are
expected during the afternoon/evening hours thru Mon, with a
30-40% chance during the afternoon and evening hours Tue and Wed.

In the SBA Channel, SCA level winds are likely in western
portions of the Channel as well as in and around the northern Channel
Islands during the late afternoon thru late evening hours thru
Wed. In eastern portions of the Channel, there is a 20-30% chance
of SCA conds late each afternoon/evening.

Across the southern inner waters, there is a 20% chance of SCA
level winds across far western portions of the zone during the
late afternoon/evening hours Sun thru Mon, then are more likely
Tue and Wed, especially from near Anacapa Island to the northwest
of Catalina Island.

The gusty winds will generate short-period, choppy seas that will
likely be dangerous to mariners through the entire holiday weekend
and into the middle of next week.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 6 AM PDT Sunday for zones
      349-351. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect from noon to 9 PM PDT Sunday
      for zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Sunday for zone
      650. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Monday for
      zones 670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Munroe/Sirard
AVIATION...Gomberg
MARINE...Gomberg/Lund
SYNOPSIS...Sirard

weather.gov/losangeles

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

NWS LOX Office Area Forecast Discussion