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000 
FXUS66 KLOX 210602
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA 
1002 PM PST Tue Feb 20 2018

.SYNOPSIS...

20/902 PM

A broad trough over the West will keep temperatures below normal 
into Saturday. Precipitation is possible on Thursday when the best
energy and moisture move over the region. High pressure will build 
in over the weekend to warm temperatures to near normal, then 
another trough should arrive Monday and bring cooler temperatures
and possible precipitation early next week.

&&

.SHORT TERM (TUE-FRI)...

20/856 PM

Shortwave ridging aloft is breaking down this evening as a weak
and mainly dry trough of low pressure over Northern California
dips south. Most of the low-level moisture will remain offshore
as the trough's land-mass track has starved it of moisture.
Mainly mid-level to high-level cloudiness will stream over the
area late tonight through Wednesday night. A few showers or
sprinkles will stream offshore tonight and into Wednesday morning.
The main story will continue to be the cold air mass in place as a
northerly flow aloft, piping colder air from Canada south into the
region, will remain intact. A few tweaks to clouds and
temperatures will be made in the latest update, but for the most
part, the forecast is in good shape.

*** FROM PREVIOUS DISCUSSION ***

A slightly stronger/colder system will come through late Thu into
Friday but again it's mostly inland so not a lot of moisture to
work with. Could see some very light showers across SLO/SB
Counties, the north slopes near the Kern County line, and eastern
LA County into early Thu otherwise just some clouds and 
increasing west to northwest winds which will generate subsiding 
air to the lee of the mountains. Snow levels will be pretty low,
around 4000 Thu then dropping to 1500-2000 feet early Fri but
limited moisture will confine accumulations to a few inches or 
less. Any precip should be tapering off Friday morning with the
exception of the Kern County line area which could see some light
precip into early afternoon with favorable wind support there.

.LONG TERM (SAT-TUE)...

20/125 PM

A quiet weekend expected with temperatures climbing back to near
normal levels by Sunday. Early next week another trough looks to
be taking a similar track as the last several systems though there
are some indications that it could still tap into enough moisture
to generate slightly more widespread, though mostly light precip.
Still a lot of uncertainty and the ECMWF wasn't available for 
comparison so didn't make much change to the forecast. Likely cool
and breezy again, especially Mon night into Tuesday.

&&

.AVIATION...

21/0601Z

At 0535Z at KLAX, there was no marine nor was there a sfc inversion.

Good confidence in CAVU TAFs.

KLAX...Good confidence in CAVU TAF. Any east winds will remain 
less than 7 knots.

KBUR...Good confidence in CAVU TAF.

&&

.MARINE...

20/856 PM

For the Outer Waters, high confidence in the current forecast. 
Small Craft Advisory level winds will continue through late
tonight or Wednesday morning. After a lull on Wednesday and
Wednesday night, winds will likely increase to advisory levels 
again on Thursday. There is a 60 percent chance of winds
strengthening to Gale Warning levels Thursday night. Small Craft
Advisory level winds are likely from Friday through Sunday.

For the Inner Waters, high confidence in current forecast. Small
Craft Advisory level winds are likely on Thursday and Thursday 
night across the northern nearshore waters. There is a 60 percent
chance of winds reaching Gale Warning levels Thu afternoon and 
Thursday night. For the Southern Inner Waters, advisory level 
winds are likely Thursday afternoon through Friday morning. There
is also a 60 percent chance of Gale Warning level winds for 
Thursday night into Friday morning.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Freeze Warning in effect until 9 AM PST Wednesday for zones
      34>36-39-40-45-46-88-547. (See LAXNPWLOX).
     Hard Freeze Warning in effect until 9 AM PST Wednesday for
      zones 38-44. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PST Wednesday for
      zones 670-673. (See LAXMWWLOX).
     Small Craft Advisory in effect until 9 AM PST Wednesday for
      zone 676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (FRI-TUE).

Rain and mountain snow could return to the area into Friday and 
again early next week, possibly making for hazardous travel in the
mountains.

&&

$$

PUBLIC...Hall/MW

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