000
FXUS66 KLOX 291414
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
614 AM PST Sun Jan 29 2023

.SYNOPSIS...29/614 AM.

A dynamic and cold, albeit moisture starved winter storm will push
through the region today through Monday morning bringing rain and
low elevation snow to the area. Scattered rain and snow showers
will linger into Monday afternoon or evening. Low elevations snow
may affect travel on many highly traveled roads through the
mountains. Gusty northeast winds may affect portions of Los
Angeles and Ventura Counties late Mon through Tuesday. Ridging
behind this system will bring warmer weather during the daytime
hours during midweek, but the nights will remain quite cold.

&&

.SHORT TERM (TDY-TUE)...29/606 AM.

The marine layer has deepened dramatically during the past 12
hours, and has now basically morphed into just a deep moist layer
across the region. Skies were cloudy everywhere except for the
higher mountain tops, and much of the Antelope Valley. Rain gauges
were showing a few locations reporting very light amounts of measurable
rain, mainly in the foothills and mtns in Los Angeles County.

A potent short wave trough and associated vort was dropping
southward thru the Pac NW early this morning. It will evolve into
a closed upper low near Redding late this morning, then drop
southward to near San Francisco late this afternoon, and to a
position just to the northwest of Pt. Conception late tonight.
Crashing heights, increasingly cyclonic flow and improving low and
mid level lift will likely bring precipitation to the entire
forecast area by tonight.

There will be a chance of light rain just about anywhere today,
with rain becoming likely in areas north of Pt. Conception this
afternoon. With favorable upslope low level flow, more widespread
precipitation is also likely across eastern L.A. County this
afternoon, particularly in the foothills and mtns.

Gusty southwest to west winds will probably reach low end advisory
level in the Antelope Valley, particularly in the foothills late
this morning through this evening, with winds possibly getting
close to advisory levels in the L.A. County mtns through the
Highway 14 Corridor. Max temps will be down significantly again
today, with highs likely 6 to 12 degrees below normal in most
areas, and locally more than 15 degrees below normal. Snow levels
will likely drop to between 4000 and 4500 feet late in the day.

Precipitation is likely across the entire region tonight, though
the chance of rain will decrease below the likely category across
SLO and most of SBA Counties late tonight as it turns more showery.

The upper low will track from just northwest of Pt. Conception
late tonight, to about 200 nm west of San Nicolas Island late
Monday morning to about 150 nm west of San Diego Mon afternoon.
With this track. the system may have a chance to pick up some
Pacific moisture, which could increase precipitation amounts.
mainly across eastern L.A. County, where the flow direction will
be best and there will be the longest fetch over water. Of course,
the trend of the models has been to the west with each run, so
there is a danger that it could track too far west. At this point,
that does not look to be the case.

While this still does not look to be a major precipitation
producer for most of the region, there will be some higher totals
in the mtns, particularly in the eastern San Gabriels, and snow
levels will be quite low, so it may be quite impactful. In
general, expect most areas to receive one third of an inch of
precipitation or less, except one third to two thirds of an inch
in the mtns and across eastern L.A. County, and one half to one
inch in the eastern San Gabriel mountains.

Expect snow levels to drop to between 3000 and 3500 feet tonight
and Mon morning, with snow possibly falling as low as 2500 feet in
heavier showers.

The low snow levels will likely cause travel problems tonight and
Mon on Interstate 5 and Highway 14 in L.A. County, and on Highway
33 in Ventura County, and to Lockwood Valley Road. Snow will
likely fall in the foothills surrounding the Antelope and Cuyama
Valleys, and possibly occasionally to the valley floor. Snow could
also affect the higher peaks of the Santa Ynez Range.

As the upper low tracks south of the region, low level flow will
turn northeasterly which could cause some upslope enhancement of
the snow across the Antelope Valley late tonight and Mon. Have
decided to expand the Winter Weather Advisory to the Antelope
Valley, where at least 1 to 3 inches of snow looks likely in the
foothills, with snow possibly occasionally reaching the valley
flow. Winter Weather Advisories are already in effect for the
interior mountains of SBA County and Ventura County for 1 to 3
inches of snow between 3000 and 4500 feet and 3 to 6 inches of
snow above 4500 feet. Across the L.A. County mtns excluding the
Santa Monicas, except 2 to 5 inches of snow between 3000 and 4500
feet, and 4 to 8 inches at 4500 feet. Local totals up to 12
inches are possible in the eastern San Gabriel Mountains, and the
Winter Weather Advisory may well have to be upgraded to a Winter
Storm Warning.

Showers will decrease in coverage from northwest to southeast across
the region Mon afternoon, with showers likely only confined to
southern and eastern L.A. County Mon evening. Monday will likely
be one of the coldest days of the winter so far across the region.
with all locations likely having highs in the 50s or lower.

Clouds will decrease by late Mon night, and Tue will be mostly
sunny and cool. Low level NE winds may be strong enough for some
low end Wind Advisories across portions of L.A./VTU Counties
prone to Santa Ana winds. Where skies clear early enough and the
winds drop off Mon night, it will be very cold, with frosts or
freezes likely in the valleys and even some interior coastal
zones. Max temps on Tue will be on the rebound but will still be
several degrees below normal everywhere.

.LONG TERM (WED-SAT)...29/555 AM.

An upper ridge will build into the region Wed and persist into Thu.
This will bring warming to the region Wed, with perhaps a touch
more warming Thu. However, max temps will still be below normal.
It will be cold both Tue night and Wed night, but especially Tue
night, when frosts are likely in the valleys of Ventura County and
possibly western L.A. County, on the Central Coast, across
interior portions of the Ventura County coastal plain and the
south coast of SBA County.

High clouds will likely increase across the region Thu as the
ridge axis moves east of the area ad a weakening trough approaches
the West Coast. The southern end of a surface front may bring
light rain to far northern areas Thu night and early Fri, but most
ensemble members do not even have measurable rain for KSBP.
Another ridge will bring some warming Sat, but that ridge will
flatten out Sun as another trough moves into the eastern Pacific.

&&

.AVIATION...29/1122Z.

At 1045Z, the marine inversion at KLAX was based at 5000 feet.
The top of the inversion was 7200 feet with a temperature of
5 degrees Celsius.

Overall, low to moderate confidence in 12Z TAF package. Deep
inversion and approaching system will bring CIG restrictions to
all sites through the TAF period. MVFR CIGs are anticipated to
develop later this morning and continue through tonight, but
timing of arrival of MVFR CIGs is low. Also, given the deep moist
layer, conditions may fluctuate between MVFR and VFR levels
through the period. Light showers are expected, beginning this
afternoon and continuing through tonight. However, timing of
shower activity is low confidence forecast.

KLAX...Low confidence in 12Z TAF. There is a 50% chance of MVFR
CIGs developing 12Z-21Z. For this afternoon and tonight, moderate
confidence in MVFR CIGs, but low confidence in timing of shower
activity. No significant easterly wind component is expected.

KBUR...Low confidence in 12Z TAF. There is a 50% chance of MVFR
CIGs developing 12Z-21Z. For this afternoon and tonight, moderate
confidence in MVFR CIGs, but low confidence in timing of shower
activity.

&&

.MARINE...29/322 AM.

For the Outer Waters, moderate to high confidence in current
forecast. Through this evening, high confidence in Small Craft
Advisory (SCA) level winds. For tonight and Monday, high
confidence in winds and seas remaining below SCA levels. For
Monday night and Tuesday, there is a 40-50% chance of SCA level
northeast winds across PZZ676. For Wednesday and Thursday, high
confidence in winds and seas remaining below SCA levels for all
the Outer Waters.

For the Inner Waters north of Point Sal, high confidence in
current forecast. There is a 20% chance of SCA level winds late
this afternoon and evening. Otherwise, high confidence in winds
and seas remaining below SCA levels through Thursday.

For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. Today through Monday, high
confidence in winds and seas remaining below SCA levels. For
Monday night and Tuesday, there is a 50% chance of SCA level
northeast winds from Ventura south to Santa Monica. For Wednesday
and Thursday, high confidence in winds and seas remaining below
SCA levels.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Winter Weather Advisory in effect from 3 PM this afternoon to
3 PM PST Monday for zones 53-353. (See LAXWSWLOX).
Winter Weather Advisory in effect from 3 PM this afternoon to
10 PM PST Monday for zone 54. (See LAXWSWLOX).
Wind Advisory in effect until 7 PM PST this evening for zone
59. (See LAXNPWLOX).
Winter Weather Advisory in effect from 10 PM this evening to
10 PM PST Monday for zone 59. (See LAXWSWLOX).
PZ...Small Craft Advisory in effect until 9 PM PST this evening
for zones 670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...DB
AVIATION...RAT
MARINE...RAT
SYNOPSIS...DB

weather.gov/losangeles

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