Wind Advisory 126, NWS Los Angeles, CA

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
831 PM PST Fri Dec 9 2022

.SYNOPSIS...09/829 PM.

A cold front will bring precipitation to all four county areas
from Saturday afternoon through Sunday. Rain totals of one to two
inches are expected in the coast and valley areas, with two to six
inches in the foothills and mountains, and over a foot of snow is
possible above seven thousand feet. Lingering rain and snow
showers are possible through Monday.

&&

.SHORT TERM (FRI-MON)...09/829 PM.

Satellite imagery showing clouds on the increase this evening
for much of Santa barbara and San Luis Obispo counties, with
clouds beginning to develop across coastal and valley areas of
LA/Ventura counties. Cross sections showing low level moisture
deepening through the night ahead of Pacific storm. Light
rain could begin across San Luis Obispo county by later tonight.

A strong and cold upper low in the Gulf of Alaska will drop
southeastward tonight and Sat reaching a position off the coast
of southwestern Oregon Saturday afternoon. The atmosphere will
become increasingly moist on Saturday as low level warm advection
helps to provide increasing ascent over the region. A developing
warm front and strengthening south to southwest low level flow will
likely cause some rain to develop well ahead of the cold front,
especially in and below terrain with a south and southwest facing
orientation. Rain will become likely across much of SLO and SBA
Counties on Saturday. The chance of rain will extend all the way
to L.A. County by Saturday afternoon.

With a diffluent upper pattern and good jet dynamics, the cold
front will hold together nicely as it pushes across the forecast
area Sat night and early Sunday. It should bring with it a 4 to 6
hour period of moderate to heavy rain. Powerful south winds to 50
to 55 knot at 850 mb will cause significant orographic enhancement
of the rainfall where the wind is perpendicular to the terrain.
This will be especially true across northwestern SLO County, and
the east to west mountain ranges and foothills from southern SBA
County through Los Angeles County, where rainfall rates of 0.5 to
1.0 inch per hour are possible. The potential for these higher
rainfall rates has prompted the issuance of the Flash Flood Watch
for the Fish and Lake burn scars in LA county, valid from 3 AM
Sunday to 6 pm Sunday. Most coastal/valley areas will likely see
peak rainfall rates between 0.25 and 0.50 inches per hour.

High Wind Watches are in effect for the mountains and Antelope
Valley Saturday afternoon and ending by Sunday afternoon for the
L.A. County mtns and Antelope Valley as the front moves through.
Damaging wind gusts of 60 to 70 mph are possible in these areas,
with the strongest winds likely focused in the LA county mountains
and foothills of the Antelope Valley.

Rain will turn to showers by Sunday afternoon and remain quite
numerous through Sun night and in to Monday. Cooling aloft and a
favorable jet position will likely cause some of the showers to be
convective, with heavy downpours and small hail possibly Sun
afternoon through Sun night. Rainfall totals should average 1 to
2 inches in coastal and valley areas and 2 to 6 inches in the
foothills and mountains.

Snow levels will be rather high (above 7000 feet) through Saturday
night Snow levels will fall quickly later on Sunday in the colder
air behind the front, likely as low as 3000 to 4000 feet by late
Sunday night into Monday, when a Winter Storm Watch is in effect.
An inch or so of snow could accumulate on portions of I-5 near
the Grapevine during this time. A few snow showers could linger
on northern slopes Mon evening, but then skies should clear.

It will be cold Mon night, and freezes are possible in the Ojai
Valley and other colder Ventura County valleys, with frosts on the
Central Coast.

.LONG TERM (TUE-FRI)...09/234 PM.

Dry and cool weather is expected Tue and Wed morning. Another
storm system forms Wednesday off the CA-OR border and may bring
rain to SLO Co as early as Wednesday evening and will probably
bring another significant amount of rain to the region by Friday.
GEFS and EC ensembles all have some rain over the area, but there
is still a great deal of spread leading to uncertainty with with
respect to timing and rainfall amounts.

While it seems like it has been quite rainy, downtown LA is just
slightly above normal precipitation for the rain year with 2.14
inches so far.

&&

.AVIATION...09/2317Z.

At 2300Z, the marine inversion at KLAX was based at 3300 feet.
The top of the inversion was 4600 feet with a temperature of
8 degrees Celsius.

Overall, low to moderate confidence in 00Z TAF package. Through
early Saturday morning, moderate confidence in return of MVFR
CIGs to coastal/valley sites, but low confidence in timing. Later
on Saturday, approaching cold front will bring the threat of rain,
and continued CIG/VSBY restrictions, to all sites with best
chances of rain from KSBA northward through Saturday afternoon.

KLAX...Low to moderate confidence in 00Z TAF. Moderate confidence
in development of MVFR CIGs overnight, but low confidence in
timing (could be +/- 4 hours of current 11Z forecast). Timing of
light rain could be +/- 3 hours of current 01Z Sunday forecast. No
significant easterly wind component is expected.

KBUR...Low to moderate confidence in 00Z TAF. Moderate confidence
in development of MVFR CIGs overnight, but low confidence in
timing (could be +/- 4 hours of current 12Z forecast).

&&

.MARINE...09/749 PM.

A storm system will impact the area Saturday through Monday.
South winds will affect all coastal waters at times Saturday
through early Sunday morning, with moderate to heavy rain and low
visibility. 6-12 hours of Gale Force Winds are likely: In evening
update, backed off onset of Gale Warning from 6 am to 9 am
Saturday for zones 645 and 673. There is a 90 percent chance of
Gale force winds from the Central Coast to San Miguel Island, 60
percent chance Channel Islands to San Nicolas Island, 40 percent
chance in the Santa Barbara Channel, 20 percent chance in the
Santa Monica Basin. Winds will turn west to northwest Sunday
through Monday with widespread SCA winds expected. There is a 50
percent chance of Gale Force winds on Monday beyond 20 miles from
shore between the Central Coast and San Nicolas Island. Scattered
showers and a 10 percent chance of thunderstorms are expected
Sunday through Monday. Seas will be building as well, and look to
peak Sunday through Monday with heights of 12 to 18 feet, except 5
to 8 feet nearshore south from Santa Barbara to Orange County.
Moderate confidence that seas and winds will subside Tuesday and
Wednesday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Wind Watch in effect from Saturday afternoon through
      late Saturday night for zones 53-344-345-353. (See LAXNPWLOX).
     Winter Storm Watch in effect from late Sunday night through
      Monday afternoon for zones 53-54-353. (See LAXWSWLOX).
     High Wind Watch in effect from Saturday evening through
      Sunday afternoon for zones 54-59. (See LAXNPWLOX).
     Flash Flood Watch in effect from late Saturday night through
      Sunday afternoon for zones 54-59-548. (See LAXFFALOX).
PZ...Gale Warning in effect from 9 AM Saturday to 3 AM PST Sunday
      for zones 645-673. (See LAXMWWLOX).
     Small Craft Advisory in effect from 6 PM Saturday to 9 PM PST
      Sunday for zones 650-655. (See LAXMWWLOX).
     Gale Warning in effect from 6 AM Saturday to 3 AM PST Sunday
      for zone 670. (See LAXMWWLOX).
     Gale Warning in effect from 3 PM Saturday to 6 AM PST Sunday
      for zone 676. (See LAXMWWLOX).

&&

PUBLIC...Gomberg/DB/jld
AVIATION...RAT
MARINE...Gomberg/Kittell
SYNOPSIS...jld

weather.gov/losangeles

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