000
FXUS66 KLOX 011345
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
545 AM PST Fri Mar 1 2024

.SYNOPSIS...01/537 AM.

A cold storm system will move through southwest California today
through Sunday morning, bringing periods of rain and mountain snow,
along with gusty to locally damaging winds. There will be a fairly
long duration of mostly light, but occasionally moderate rain and
snow. The heaviest precipitation is expected late tonight through
Saturday evening. Dry and cool weather should follow late Sunday
and continue through least early Tuesday. There is another chance
of rain later Tuesday into early Thursday, but confidence in the
details of that system are low. At this point, it looks as though
it would only bring light precipitation to the area.

&&

.SHORT TERM (TDY-SUN)...01/544 AM.

Skies were mostly cloudy across the region early this morning,
except still partly cloudy in the Antelope Valley, the far
interior valleys of SLO and SBA Counties, and some higher mountain
locations. Skies will likely become mostly cloudy in those areas
by afternoon. Gusty southwest winds have developed in the
Antelope Valley and in the mtns, but so far were below advisory
level. Light rain has spread into SLO County and northern SBA
County early this morning, and there was patchy drizzle elsewhere.

A very cold upper low was located about 500 NM W of Vancouver
early this morning, with a trough extending southward through the
eastern Pacific to the west of CA. The upper low will drop slowly
south southeastward today, and will be located about 400 NM W of
Seattle late this afternoon. Its associated trough will continue
to dig southward, causing heights across the forecast area to
fall. Increasing southwest to west flow aloft will bring a
deepening layer of moisture into the forecast area as the day
progresses. As the heights fall, mid level lift will increase,
which should cause rain to become more widespread from north to
south later today. Rain will become likely in most areas this
afternoon, though there is still just a chance of rain across
L.A. County this afternoon. Southwest winds will increase, and
will likely reach Wind Advisory levels across the valleys and
mountains of SLO/SBA Counties, the northern mountains of Ventura
County, the Antelope Valley and adjacent foothills, and most
mountain areas of L.A. County. Wind gusts of 45 to 50 mph are
expected by late afternoon, except 35 to 45 mph in the valleys of
SLO/SBA Counties. Snow levels should remain above 6000 feet for
most of the day, with local snow accumulations of 1 to 3 inches
above 6000 feet by evening. The highest snow totals through this
evening will be in the northern mountains of Ventura County, where
a Winter Weather Advisory begins at noon today.

The upper low will move slowly eastward tonight thru Sat night,
with a couple of distinct short wave troughs rotating around it
into the Pacific Northwest. Meanwhile, the associated trough will
continue to deepen down the West Coast through Sat night, with the
southern end of a couple of frontal systems pushing into forecast
area. This will bring rain to the region much of the time tonight
through Sat night. Rain will be mostly on the light to moderate
side, but there could be some heavier embedded showers late
tonight into Saturday evening, as colder air aloft brings
increasing instability to the region. At this point, there is no
mention of thunderstorms in the official forecast, because the
best dynamics and coldest air aloft will remain to the north of
the forecast area. However, it is not a zero percent chance, and
if any thunderstorms occur, they would be most likely Sat into Sat
evening. Steady rain will decrease late Sat night, then turn to
scattered showers Sun. Skies may become partly cloudy in some areas
Sun afternoon. It will be very chilly today thru Sun, with max
temps 6 to 12 degrees below normal in most areas, and locally 15
to 20 degrees below normal Sat and Sun.

Rainfall totals of one half inch to one inch are expected in most
areas, with 1.0 to 2.5 inches in the foothills and mtns, highest
in eastern L.A. County and across SLO/SBA Counties. In northwestern
SLO County, rainfall totals of 2.5 to 4 inches are likely.

Snow levels will lower to 5000 to 5500 ft by Sat, then to 4000 to
4500 feet Sat night and early Sunday. Winter Storm Warnings are
in effect for the eastern San Gabriel Mountains, where there is a
good chance of 8 to 16 inches of snow above 7000 feet, and 4 to 8
inches of snow above 5500 feet. Light snow accumulations are
possible at elevations as low as 4500 feet late Sat thru Sun
morning. In the Ventura County mountains, there will be somewhat
less precipitation, so A Winter Weather Advisory is in effect for
4 to 8 inches of snow above 5500 feet. At this point, it appears
that there is only a 10% chance of accumulating snow affecting I-5
through the Grapevine. In addition to the snow, wind gusts to 60
to 65 mph are likely in the eastern San Gabriel Mountains at
times late this evening thru Sun morning.

Winds will remain gusty thru Sun morning, so wind advisories will
remain in effect for the areas earlier mentioned thru Sun morning.
Wind advisories may have to be expanded late tonight and Sat to
include the Central Coast, the Salinas Valley, and the Santa
Clarita Valley. In the foothills above the Antelope Valley, and
through the Highway 14 Corridor, winds are expected to increase to
damaging levels tonight, with gusts to 60 to 65 mph at times from
late this evening through at least Sat night. Therefore the High
Wind Watch for those area has been upgraded to a High Wind Warning.

.LONG TERM (MON-THU)...01/526 AM.

With lots of low level moisture lingering into Sun night, skies
should remain partly to mostly cloudy. A few model ensemble
members keep some shower activity in northern areas and in the
mtns, but those are a minority, and it is most likely to be dry.

Westerly flow aloft will set up over the region Mon. It should be
a dry and cool day, with partly cloudy skies, and some gusty NW
winds across southern SBA County and through the I-5 Corridor.

The operational runs of the EC and GFS show some big differences
beyond Mon night. The EC shows an upper low moving thru the
eastern Pacific Mon night pushing into northern CA Tue. Some light
rain with the southern end of its associated surface front could
push into areas N of Pt. Conception as early as Tue afternoon.
Another upper trough will follow quickly on its heels Tue night,
the close off and track across Central CA Wed. This system will
track a bit farther south than the first one, and could bring rain
to the entire area Tue night into Wed night. After lingering showers
Thu morning, drier weather will follow later Thu as the upper low
moves into Nevada, and northerly flow filters into the area.

On the other hand, the GFS shows a weaker trough moving into the
Pac NW Tue, well to the north of the forecast area, with dry and
cool weather Tue. It shows an upper low dropping southeastward
thru the eastern Pacific, to a position about 450 NM WSW of Pt.
Conception late Tue night. It shows that system tracking south of
the region Wed/Wed night, with most if not all of its rain passing
south of the area. Another upper low will drop southeastward into
northern CA Thu, but take an inside-slider track, with no southerly
low level flow. It would bring just a chance of showers Thu. At
this point, the ensembles are little help since there is a lot of
variability. For now, have gone with a slight chance of rain Tue
night thru Wed night, with a slight chance of showers Thu, but
that is a very low confidence forecast and is subject to change.

&&

.AVIATION...01/1304Z.

Around 12Z, there was a deep moist layer up to around 5100 feet
deep. The remnant marine inversion was up to around 6700 feet with
a temperature near 6 degrees Celsius.

Low-to-moderate confidence in current forecast. MVFR to VFR
conditions with ceilings at or below 6000 feet are likely through
the period. There is a moderate-to-high (30-50 percent) chance of
IFR conditions in rain. Gusty southwest winds will develop through
this evening, and there is a chance of moderate low-level wind
shear and turbulence at desert terminals after 20Z.

KLAX...MVFR to VFR conditions with ceilings at or below 6000 feet
are likely through the period. There is a 30 percent chance of
IFR conditions in rain through 18Z, and again after 03Z Saturday.
Any east winds should remain less than 7 knots, but there is a 10
percent chance of east winds between 7 and 9 knots. After 07Z
Saturday, there is a 40 percent chance of southerly winds greater
than 10 knots.

KBUR...MVFR to VFR conditions with ceilings at or below 6000 feet
are likely through the period. There is a 30 percent chance of
IFR conditions in rain through 19Z, and again after 05Z Saturday.
There is a 20 percent chance cross winds between 22Z and 02Z
Saturday.

&&

.MARINE...01/504 AM.

Moderate-to-high confidence in the current forecast. Higher
confidence in seas relative to winds.

Wind and seas will gradually increase to Small Craft Advisory
(SCA) levels through early Saturday. There is a 70-100 percent
chance of SCA winds and seas by Saturday afternoon, increasing
from northwest to southeast through Saturday. Widespread SCA
conditions will likely affect the waters through early Monday
with hazardous seas greater than 10 feet being common across most
of the coastal waters by Sunday evening.

Winds will diminish between Sunday night and Monday, but there is
a 50-80 percent chance that hazardous seas may linger through at
least Monday night across the outer waters. There is a 30 percent
chance of seas across the outer waters remaining at or just below
SCA levels through at least Wednesday.

Another storm system will be possible as early as Wednesday night
into early next weekend, possibly bringing hazardous conditions
to the coastal waters. Confidence in exact details is still very
low at this time.

&&

.BEACHES...01/524 AM.

A west to northwest swell with a moderate period of 12-14 seconds
rapidly increase surf between through Saturday, and then surf
will remain high throughout the weekend. Surf heights will peak on
Saturday for beaches north of Point Conception and on Sunday for
beaches South of Point Conception. For the Central Coast, surf
heights will reach 12-18 feet with local damaging sets to 20 feet
across west and northwest facing shores. South of Point
Conception, surf will generally range from 4-7 feet during the
peak of the event, except 7-10 feet across west facing shores in
Ventura County. High Surf Advisories have been issued for all
beaches, especially for Saturday and Sunday when the highest surf
is expected.

There is a low-to-moderate chance of minor coastal flooding along
the immediate coastline at the time of overnight high tide
(Midnight-2AM) through Saturday night. This would primarily be for
beaches most susceptible to west to northwesterly wave energy,
highest chances for beaches near Cayucos and Morro Bay.

In the extended outlook, there is a potential for another high
surf and/or coastal flood event sometime for late next week and
into the weekend. Swell models have been struggling to get a
handle on the specific details, but there is a moderate-to-high
chance for high surf sometime between Wednesday night and Saturday
with a low-to-moderate chance of coastal flooding. For the middle
to latter parts of next week, it is best to continue to monitor
the latest information from the National Weather Service.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect from 4 PM this afternoon to 10 AM PST
Sunday for zones 38-344-345-353-378. (See LAXNPWLOX).
High Surf Advisory in effect from 10 AM Saturday to 8 AM PST
Monday for zones 87-349-350-362-366. (See LAXCFWLOX).
High Surf Advisory in effect until 5 PM PST Monday for zones
340-346. (See LAXCFWLOX).
High Surf Advisory in effect from 4 PM this afternoon to 8 AM
PST Monday for zone 354. (See LAXCFWLOX).
Winter Weather Advisory in effect from noon today to 10 AM
PST Sunday for zone 377. (See LAXWSWLOX).
Wind Advisory in effect from 4 PM this afternoon to 10 PM PST
this evening for zones 379-381-382. (See LAXNPWLOX).
High Wind Warning in effect from 10 PM this evening to 1 PM
PST Sunday for zones 379-381-382. (See LAXNPWLOX).
Winter Storm Warning in effect from 6 PM this evening to 10
AM PST Sunday for zone 380. (See LAXWSWLOX).
Wind Advisory in effect from 4 PM this afternoon to 1 PM PST
Sunday for zone 383. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect from 9 AM this morning to 9 AM
PST Monday for zone 645. (See LAXMWWLOX).
Small Craft Advisory in effect from 9 PM this evening to 9 AM
PST Monday for zone 650. (See LAXMWWLOX).
Small Craft Advisory in effect from 3 AM Saturday to 9 AM PST
Monday for zone 655. (See LAXMWWLOX).
Small Craft Advisory in effect until 3 PM PST Monday for zone
670. (See LAXMWWLOX).
Small Craft Advisory in effect from 9 AM this morning to 3 PM
PST Monday for zone 673. (See LAXMWWLOX).
Small Craft Advisory in effect from 3 PM this afternoon to 9
AM PST Monday for zone 676. (See LAXMWWLOX).

&&

$$

PUBLIC...DB
AVIATION...Hall
MARINE...Hall
BEACHES...Hall
SYNOPSIS...DB

weather.gov/losangeles

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