Area Forecast Discussion
Issued by NWS Los Angeles, CA

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730
FXUS66 KLOX 250105
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
505 PM PST Sat Feb 24 2018

.SYNOPSIS...24/326 PM.

Winds will be breezy through early Sunday along the Central Coast
and portions of Ventura and Los Angeles Counties. After another night
of very cold temperatures in wind sheltered areas, afternoon temperatures
will be near normal on Sunday then cool to below normal through the
work week. Breezy winds and a chance of light precipitation return to
the region Monday and Tuesday, then again Thursday through Saturday.
Snow levels will be at or below some passes at times this week.

&&

.SHORT TERM (TDY-TUE)...24/127 PM.

Another cold night is expected tonight, but with some influx of
moisture and 500 MB heights on the rise, temperatures should be
up a few degrees compared to last night. A few isolated coastal
and valley areas will approach freezing, with the Ojai Valley
being the coldest and Frost Advisory will be issued.

Moderate north-to-south surface pressure gradients will continue
to generate breezy northwest to north winds through this evening,
then weaken become more northeasterly Sunday morning as the east-
to-west gradients strengthen. Besides the mountains in the
morning, not expecting the northeast winds to be near advisory,
but they should team up with a warmer airmass to push temperatures
to around normal for the first time since last Sunday. Highs near
70 should be common over the coastal and valley areas under
mostly sunny skies.

A cold low pressure system currently over the Gulf of Alaska will
drop into Northern California on Monday, then sweep through
Southern California on Tuesday. This track, like the last few
systems we have had, is extremely troublesome with precipitation
potentials highly sensitive to just a shift of a 100 miles in the
track. The 00Z ECMWF teased us with the more westerly and wetter
track, but the 12Z run has popped back inland a little and matches
perfectly with the GFS. Still expecting some wobbling in the
projections as we get closer, but the stability of the GFS
solution and the way this winter has been going puts a lot of
favor in the GFS solution. So the most likely picture for Monday
and Tuesday is a lot like what happened Sunday and Monday of this
week. Moist west-to-northwest flow should bring showers to areas
north of Santa Barbara, the Tejon Pass, and possibly far eastern
LA County. There is a decent chance that Ventura and southern SBA
will be in the rain shadow of the northwest flow and mostly dry
from this. The storm track and position in the current models
would suggest the possibility of wrap-around moisture with
precipitation for the Antelope Valley. Advisory level snow cannot
be ruled out either for the Interstate 5 Corridor in the Los
Angeles and Ventura County Mountains and across the Antelope
Valley. During the day on Tuesday, will keep 20-30 PoPs over much
of the area in case there is a drift off shower or two like what
occurred last Monday. Rainfall totals will be highly variable with
about 0.33 inch on the upper end of the rain, but most of the
area should be less than 0.20 inch range. Snow levels look low,
down to 2,500 feet Monday night into Tuesday, and 1-3 inches is
possible on the north slopes of the Ventura and LA County
Mountains...including the I-5 Tejon Pass. The thunderstorm
potential is not zero, but not high enough to mention in the
forecast. There will be some gusty winds during this time, but it
does not look as windy as earlier this week. Maybe Santa Barbara
County and the LA/Ventura Coastal areas will need a low end wind
advisory, but that looks about it for now. Daytime temperatures
will be down from the Sunday peak, by about 10 degrees or so, but
night time temperatures should be up with the increased moisture.

.LONG TERM (WED-SAT)...24/127 PM.

Sub-freezing temperatures look likely over some coastal and
valley areas in the morning, otherwise Wednesday looks pretty
benign sitting between the two weather systems of note, with below
normal temperatures and locally breezy southwest flow.

Still expecting a cold low pressure system parking itself off
Washington state by Thursday, then slowly pushing to the east
Friday and Saturday. The position of the low remains favorable for
a cold front moving down the California coast Thursday into Friday,
with a decent chance of it holding together through southern
California. Confidence is growing for some widespread rain, but
confidence is still low as to how much as computer projections
continue to vary from run-to-run. With that said, the potential
exists for moderate rainfall with several of the course resolution
ensemble members showing about one inch or more for the area. If
the wetter solutions hold out, debris flows will threaten areas
around recent burn scars, but more likely of the minor variety.

Shower chances look to linger Friday night into Saturday with
moist westerly flow sticking around. Temperatures will remain
below normal.

&&

.AVIATION...25/0104Z.

At 00Z, the marine layer depth around 630 feet.

VFR conditions are expected throughout the period, except for a
chance of VLIFR conditions at KPRB. There is a chance of moderate
wind shear and turbulence at all terminals through 18Z.

KLAX...VFR conditions are expected throughout the period. There
is a 30 percent chance of moderate wind shear and turbulence
between 07Z and 12Z. Any east winds should remain less than 7
knots.

KBUR...VFR conditions are expected throughout the period. There
is a 30 percent chance of moderate wind shear and turbulence
between 05Z and 13Z.

&&

.MARINE...24/105 PM.

For the Outer Waters, moderate confidence in current forecast.
Small Craft Advisory (SCA) level northwesterly winds this
afternoon should increase to Gale Warning levels by sunset and
continue this evening. SCA winds should then persist late tonight
through Thu, although there is a 40% chance of Gale force gusts
Monday afternoon through Tue.

For the Inner Waters, generally high confidence in current
forecast. For the waters north of Point Sal, SCA level northwest
winds are expected each afternoon/evening from today through
Tue. For the waters south of Point Conception, there is a 70%
chance of SCA level winds this afternoon/evening for zone PZZ650,
with a 30% chance of SCA gusts western portions of PZZ655. From
Monday afternoon through Tuesday night, there is a 60% chance of
SCA level winds, especially across western sections during the
afternoons and evenings.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 9 PM PST this evening for zones
      34-35. (See LAXNPWLOX).
     Frost Advisory in effect from 1 AM to 9 AM PST Sunday for
      zone 44. (See LAXNPWLOX).
     Wind Advisory in effect until 10 AM PST Sunday for zones
      53-54. (See LAXNPWLOX).
     Wind Advisory in effect until 3 AM PST Sunday for zone 59. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 9 PM PST Monday for zone
      645. (See LAXMWWLOX).
     Small Craft Advisory in effect until 9 PM PST this evening
      for zone 650. (See LAXMWWLOX).
     Gale Warning in effect until 9 PM PST this evening for zones
      670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (TUE-SAT).

A cold storm system will bring light precipitation to the area
into early Tuesday. Snow is possible down to the 2,500 foot
elevation, which would affect mountain pass travel, as well as
gale force winds and dangerous sea conditions. There could be
frost or freeze across the region Tuesday night and early Wed.
Another storm is expected Thursday into Friday, with potentially
moderate rain and a chance for flooding issues.

&&

$$

PUBLIC...Kittell/Hall
AVIATION...Hall
MARINE...Sirard
SYNOPSIS...Kj

weather.gov/losangeles



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