280
FXUS66 KLOX 121559
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
859 AM PDT Wed Mar 12 2025

.SYNOPSIS...12/356 AM.

A series of storm systems will bring periods of rain, mountain
snow, gusty winds, and much colder temperatures through the end
of the week and possibly into the weekend. The strongest system
will move into the area tonight into Thursday morning with rain
and snow heavy at times, and potentially damaging across the
interior valleys and mountains.

&&

.SHORT TERM (TDY-FRI)...12/526 AM.

A cold low pressure system sits over the eastern Pacific and along
the West Coast this morning. The trough, sitting near 39N and
132W, will move over the region through Thursday. Light
precipitation will increase in coverage today as a weak warm
frontal boundary moves over the region. PoPs have been nudged much
higher over the previous forecast for today as high-resolution multi-
model ensemble members suggest high probabilities for measurable
rain. Some weak echoes are present on the latest radar mosaic, but
the radar beam is very likely above the depth of the shower
activity.

The cold frontal band sits off the California coast this morning
and stretching out to the southwest. A few lightning strikes are
already being observed along the frontal boundary and behind it with
the trough currently. Sub-tropical moisture can be seen starting
to interact with the front early this morning as the storm moves
southeast into the region. GOES precipitable water imagery suggest
values on the order of 0.8-0.9 inch currently. This agrees well
with EPS/GEFS ensemble precipitable water value means which
indicate values expected to top out between 0.8-1.0 inch. This
would be on the order of 125-150 percent of normal for this time
of year. As the front moves closer to the California later today,
a difluent flow pattern will develop along the Central Coast, then
spread south into Southland through Thursday morning. The forecast
is pretty much unchanged offering up a definite chance of rain and
mountain snow, but a few tweaks were made to adjust for the
timing of the storm. The latest model solutions are speeding up
the storm movement slightly and there is some concern that the
storm QPF amounts could be overdone slightly. While the forecast
stays consistent with 1 to 2 inches of rain across the coast and
valleys with up to 2 to 4 inches, amounts were ticked down
slightly as the storm is moving a tad faster. Maximum hourly
rainfall rates DO NOT change though, remaining consistent toward
values exceeding 0.50 inch/hour. There is a high chance of
rainfall rates exceeding 0.75 inch which is favorable to create
flooding in urban areas and cause significant debris flow on
recent burn scars. A flood watch will remain in effect for areas
south of Point Conception, including the recent burn scars, such
as the Eaton and Palisades burn areas. In addition, isolated
thunderstorms are possible due to the difluent flow pattern and
the colder air mass aloft being ushered in.

A low-level jet approaching 35-50 knots at 850 mb will push into
the region along the front later today and into tonight. High Wind
Watches were converted to a High Wind Warnings across interior
San Luis Obispo County between this afternoon and late tonight,
while wind advisory headlines were issued for all remaining areas
outside of the Winter Storm and High Wind Watches north of Point
Conception. A wind advisory was also added for the lower mountain
areas, such as the Santa Susana and Santa Monica mountain ranges
and the Antelope Valley. With 850 mb winds approaching 40-50 knots
across the Antelope Valley, a high wind watch was added for late
tonight for the southwesterly winds, but there is another period
of potentially damaging west to northwest winds that could affect
the Antelope Valley on Thursday afternoon.

Snow levels will still remain high initially with a potential for
one to two feet of snow above 6500 feet, but behind the front on
Thursday, snow levels will crash to between 2500 and 3500 feet.
While the Winter Storm Warning handles the heavy snowfall expected
along with gusty and potentially damaging winds across the
mountains from late today through Saturday morning, there is a
high chance that Winter Weather Advisories may be needed for the
lower mountain passes and into interior San Luis Obispo County.
There is growing concern that accumulating snow could occur on
Highway 58 across the Carrizo Plain, Highway 166 in the Cuyama
Valley, and Highway 154 near the San Marcos Pass, especially as
the colder air aloft punches in on Thursday morning and again
Thursday night.

Another weak and cold storm system will move over the region
between Friday and Saturday and bring another chance of light
rainfall across the area. The forecast goes with NBM values for
now to focus detailed attention on the short-term hazards with
the immediate storm, but a cooler and showery pattern will
redevelop.

.LONG TERM (SAT-TUE)...12/527 AM.

High pressure aloft will establish over the weekend and bring a
drying trend for Saturday and Sunday. Gusty northerly winds are
likely to persist into Saturday morning through the Interstate 5
Corridor and possibly across southern Santa Barbara County.

Another storm system will move into the region early next week. The
latest ensemble members are skewing the storm to affect the
northern areas between Monday and Tuesday. While still more than
half of the EPS members have precipitation for KOXR and KLAX,
virtually almost all of the members of the EPS, GEFS, and CMC
ensembles have precipitation for KSBP and KSDB. Stay tuned as this
storm could bring colder temperatures and gusty winds to the
region.

&&

.AVIATION...12/1141Z.

At around 08Z at KLAX, there was no marine layer or inversion.

Low confidence in TAFs. High uncertainty in timing of rain due to
spotty showers forming over the region during the period. Higher
confidence in RA to +RA beginning at northern sites first and then
working southward. Gusty SW to SE winds will pick up in the
morning and impact the terminals most of the period until the
front passes. Then, winds will quickly turn NW to W winds and
precip intensity should lighten up. Cigs and vsbys may vary
frequently when rain is occuring. IFR to MVFR conds are the most
likely worst conditions for most of the period, but heavier rain
may decrease conds to as low as VLIFR at times.

There is a 10-20% chance for thunderstorms beyond 00Z. Any
thunderstorm may produce gusty, erratic winds, small hail, and
lightning.

KLAX...Low confidence in TAF. -SHRA is possible at any point and
IFR to MVFR conds are possible at any point during rainfall. RA to
+RA will begin impacting the terminal after 06Z as the front
rolls through, and conds may be as low as VLIFR. Winds will
remain generally from the east before switching more southerly
around 18Z-20Z. Gusts up to 20 kt are possible, especially after
03Z. Then, a rapid shift to west winds will occur around 12Z, with
gusts up to 25 kt possible. West winds and light rain will then
prevail through the remainder of the period.

KBUR...Low confidence in TAF. -SHRA is possible at any point and
IFR to MVFR conds are possible at any point during rainfall. Gusty
winds from a southerly direction are likely after 18Z, but may
occur as early as 15Z. RA to +RA will begin shortly after 06Z and
conds may be as low as VLIFR during this time. Winds will shift
more westerly upon the passage of the front towards the end of the
period.

&&

.MARINE...12/858 AM.

Hazardous sea conditions through Friday. Stay in safe harbor.
Wait for the weekend with improved conditions.

Very confused seas will continue through Thursday, with a combo
long period northwest to west swell and short period southwest
swell along with southerly wind waves.

A moderate to strong cold front will move through the area from
northwest to southeast beginning this afternoon through the
overnight hours. All areas will see at least a few hours of high
end Small Craft Advisory (SCA) level south winds today, with low
end Gale Force winds expected north of Point Conception. For the
waters south of Point Conception, there is a 40-50% chance of
brief Gale Force winds as the front passes through the region, but
winds will be localized and short lived, thus a Gale Warning will
not be issued at the moment. Rain will be heavy at times, with a
chance of thunderstorms (through Thursday afternoon) and
associated hazards like locally strong winds, lightning, and
waterspouts.

Post-frontal west to northwest winds will quickly form tonight
into Thursday, with a 40-60% chance of reaching Gale Force south
of Point Conception. Best chances in zones PZZ650/655 especially
for the nearshore waters from Ventura to Santa Monica.

Another storm will move through the area on Friday, with another
round of gusty south winds and post frontal west to northwest
winds. Winds should be weaker than today/Thursday, but SCA-levels
are likely over most waters.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 10 PM PDT this evening for
      zones 38-340>343-346>349-351. (See LAXNPWLOX).
     Flood Watch remains in effect from 6 PM PDT this evening
      through Thursday afternoon for zones
      87-88-349>352-354>358-362-366>375-378>380-548. (See LAXFFALOX).
     High Surf Advisory in effect from 9 PM this evening to 9 PM
      PDT Friday for zones 340-346. (See LAXCFWLOX).
     High Wind Warning in effect from 2 PM this afternoon to 2 AM
      PDT Thursday for zones 344-345. (See LAXNPWLOX).
     Winter Storm Warning remains in effect from 4 PM this
      afternoon to 5 AM PDT Saturday for zones 353-376>382. (See LAXWSWLOX).
     High Surf Advisory in effect from 9 AM Thursday to 3 PM PDT
      Friday for zones 354-362-366. (See LAXCFWLOX).
     Wind Advisory in effect from 10 PM this evening to 6 AM PDT
      Thursday for zones 369-370-375. (See LAXNPWLOX).
     Wind Advisory in effect from 3 PM this afternoon to midnight
      PDT tonight for zone 383. (See LAXNPWLOX).
     High Wind Watch in effect late tonight for zone 383. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until noon PDT today for zones
      645-670-673. (See LAXMWWLOX).
     Gale Warning in effect from noon today to 9 PM PDT this
      evening for zones 645-670-673. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 PM this afternoon to
      noon PDT Thursday for zones 650-655. (See LAXMWWLOX).
     Gale Watch in effect from Thursday afternoon through Thursday
      evening for zones 650-655. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 PM this afternoon to 9
      AM PDT Thursday for zone 676. (See LAXMWWLOX).
     Gale Watch in effect from Thursday morning through Thursday
      afternoon for zone 676. (See LAXMWWLOX).

&&

$$

PUBLIC...Hall
AVIATION...Lewis
MARINE...Phillips/Lewis/Black
SYNOPSIS...Hall

weather.gov/losangeles

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