Acton Weather

000
FXUS66 KLOX 070633
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1033 PM PST Wed Dec 6 2023

.SYNOPSIS...06/741 PM.

A weak weather disturbance will continue to move over the region
tonight into Thursday, leading to some light showers along the
Central Coast and the northern mountain slopes. Widespread
significant cooling is then expected through Friday. Gusty
northerly winds will affect portions of the area Thursday and
Friday, strongest in the mountains, then shifting to a Santa Ana
wind event this weekend with warming temperatures.

&&

.SHORT TERM (WED-SAT)...06/804 PM.

***UPDATE***

A weak weather disturbance moving over the area has produced very
light rain along the northern Central Coast foothills, with Rocky
Butte picking up 0.08 inch of rain over the past few hours. The
light rain could continue through the next hour or two. As this
system moves further inland, light showers may affect the northern
mountain slopes along the Kern County line later tonight into
Thursday morning. Amounts there will be under 0.10 inch, and
likely just a few hundredths.

The main changes to the forecast package for this evening were to
bump up winds across southwestern Santa Barbara County, and to
issue a Wind Advisory for tonight through 8 AM Thursday. Gusts to
45 mph are expected through and below passes and canyons near
Refugio and Gaviota. Winds are expected to increase significantly
from the north to northeast Thursday afternoon, with potentially
damaging wind gusts up to 70 mph over the Montecito Hills, through
the Interstate 5 Corridor, and over the higher Ventura Mountains.
Gusty winds will also affect some of the coasts and valleys, most
notably in western LA County from Santa Clarita to LAX.

***From Previous Discussion***

Increasing northerly winds are expected following the frontal
passage Thursday, peaking in strength Thursday night into early
Friday. Per the usual north wind scenario, the strongest of these
winds will be in the mountains from Santa Barbara to LA County,
but with gusty winds filtering down into the valleys and some
coastal areas, including even the Central Coast from San Luis
Obispo south. Forecast LAX- BFL gradients are close to -7mb with
40-60kt of wind between 850-500mb and strong subsidence as well to
drive those winds to the surface. A high wind watch was posted
earlier for the mountain areas and expecting peak gusts to as high
as 60-70 mph through the Grapevine and in the hills above
Montecito. Will likely (60-80% chance) need some wind advisories
for lower elevations as the winds filter down through the canyons
into the valleys. Breezy north winds expected to reach West LA
again early Friday morning but likely peaking at around 30 mph.

Winds expected to weaken somewhat later Friday morning into
afternoon but then pick up again Friday into Saturday as the north
winds shift to northeast and the next Santa Ana event begins.
With the shift to northeast winds will be stronger in some areas,
particularly the LA/Ventura valleys and coastal areas, but weaker
across SLO and Santa Barbara Counties and the I5 corridor region.
Will likely (60-80% chance) need another round of wind advisories
for this event Saturday and possibly for Sunday as well.

The cooling trend will continue through Thursday, then level off
Friday and start to climb Saturday, mainly south and west of the
mountains due to compressional heating effect from the downsloping
winds.

.LONG TERM (SUN-WED)...06/213 PM.

Offshore flow to varying degrees will dominate the period through
the middle of next week. The weekend Santa Ana will peak Saturday
but with continued gusty and still possibly advisory level winds
into early Sunday afternoon in LA/Ventura Counties. Temperatures
will warm up a few degrees Sunday, generally 70s across most
coast/valley areas, as a ridge of high pressure encompasses most
of the western third of the US.

That ridge will break down Monday with weaker though still present
offshore flow with similar temperatures as Sunday. A weak upper
low will move into the Great Basin Tuesday and begin the process
towards another Santa Ana wind event next Wednesday. At this point
it doesn`t look quite as strong as the previous couple of events
but there is a potential for better cold air advection due to it`s
path through the Great Basin into northern AZ.

&&

.AVIATION...07/0223Z.

At 2319Z at KLAX, the marine inversion was 1100 ft deep, with an
inversion top at 2500 ft with a maximum temperature of 18 C.

Low to moderate confidence in coastal/valley TAFs, moderate to
high confidence in deserts. There is a 30% chance that cigs come
in a category lower than forecasted, and a 30% chance of
BKN008-BKN0015 cigs from 12-17Z at KBUR and KVNY. Timing of onset
of cigs may be off by +/- 3 hours.

KLAX...Low to moderate confidence, as onset of cigs may be off by
+/- 3 hours. There is a 20% chance of no cigs developing, and a
30% chance of an east wind component of 6 kts 09Z-17Z.

KBUR...Low to moderate confidence, as there is a 30% chance of
BKN008-BKN015 cigs from 12-17Z.

&&

.MARINE...06/1033 PM.

For the Outer Waters, moderate to high confidence in forecast.
Small Craft Advisory (SCA) level seas will continue into Saturday.
Tonight winds will expand across all the outer waters and last
through Friday, with a 70% chance of GALE FORCE winds for the
southern outer waters. SCA winds will start to fall off sometime
Saturday, with a 20% chance of lasting into Sunday.

For the Inner Waters north of Point Sal, moderate confidence in
forecast. SCA level seas are expected to last through Friday.
There is a 40% chance of SCA winds tomorrow afternoon into early
Friday morning, followed by a 20% chance of SCA level NE winds
nearshore Friday night into Saturday morning.

For the Inner Waters south of Point Conception, moderate to high
confidence in forecast. NW SCA level winds are occuring for the
western Santa Barbara Channel, expanding to the western portions
of all the southern inner waters by tomorrow afternoon and
evening. Tomorrow night into Friday morning, there is a 30-40%
chance of N to NE SCA level winds, from Malibu to Santa Monica,
possibly extending south to Catalina Island. Winds will shift NE
Friday night lasting through Sunday morning at least, and will be
strongest during the overnight to morning hours. There is a
70-90% chance of SCA winds from Ventura to Santa Monica and out
past Anacapa Island, and a 40-50% chance of GALE FORCE winds from
Port Hueneme to Malibu. There`s a 30% chance of SCA winds
extending from Orange County out to Catalina Island. High seas
expected, especially during winds through Sunday.

&&

.BEACHES...06/929 PM.

Long period NW swell (18-21 seconds) will affect the coastal
waters through Thursday. Expect 10 to 14 feet for Central Coast
beaches, 5 to 8 feet with local sets to 9 feet for Ventura County
beaches, and elevated surf of 3 to 6 feet for LA County beaches.
There is a 40% chance of high surf lingering into Friday
afternoon. Surf heights will be highest across west and northwest
facing beaches. Due to low astronomical tides, any coastal
flooding will be very minimal.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory in effect until 2 AM PST Friday for zones
      340-346-354. (See LAXCFWLOX).
     Wind Advisory in effect until 8 AM PST Thursday for zones
      349-351. (See LAXNPWLOX).
     High Wind Watch in effect from Thursday afternoon through
      Friday morning for zones 352-353-377-378. (See LAXNPWLOX).
     Beach Hazards Statement in effect through late Thursday night
      for zones 362-366. (See LAXCFWLOX).
PZ...Small Craft Advisory in effect until 3 AM PST Friday for
      zones 645-670. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PST Thursday for
      zone 650. (See LAXMWWLOX).
     Small Craft Advisory in effect from 1 PM Thursday to 3 AM PST
      Friday for zone 655. (See LAXMWWLOX).
     Small Craft Advisory in effect until 1 PM PST Thursday for
      zones 673-676. (See LAXMWWLOX).
     Gale Warning in effect from 1 PM Thursday to 3 AM PST Friday
      for zones 673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...MW/Lund/Smith
AVIATION...Schoenfeld
MARINE...Sweet/Schoenfeld
BEACHES...Sweet/Schoenfeld
SYNOPSIS...MW/KL

weather.gov/losangeles

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