Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 220017
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
417 PM PST Wed Feb 21 2018

.SYNOPSIS...21/1122 AM.

Temperatures will remain mostly below normal as a series of dry
cold fronts will continue to pass over the area.

&&

.SHORT TERM (TDY-SAT)...21/153 PM.

Trough moving through the area today causing nothing more than a
few stratocu clouds and possibly a few sprinkles over the eastern
San Gabriel Valley, otherwise a quiet weather day with temps a
couple degrees warmer than yesterday on average. Overnight lows
tonight expected to be a few degrees warmer overall but still some
areas of frost and near freezing temps along the Central Coast
tonight. Will likely need a frost advisory for that area later
tonight.

Another trough, this one a little colder and wetter will come
through late Thursday into Friday morning. Like this one (and many
before it) it will take a mostly inside track through the Great
Basin so it doesn`t have a lot of moisture to work with and mostly
west to northwest flow which isn`t conducive to precip,
especially south of Pt Conception. Still, some pops are warranted
and it will likely sprinkle or shower in many places by early
Friday with the best chances in the north, eastern LA County, and
the north facing slopes near the Kern County. This include the
Grapevine which should see some light snow showers Thu night into
Friday morning as the snow level will be at or just below 3000 ft.
Snow amounts likely to be 1-2" at most but impacts still expected
on Interstate 5 over the Grapevine and other mountain roads in
that area. Rain amounts at lower elevation expected to be a
quarter inch or less and in most areas much less.

Gusty west to northwest winds will develop during the day Thursday
possibly reaching advisory levels near the coast, southern SB
County, and in the Antelope Valley.

After the second trough moves through Friday morning low level
winds will shift to north and northeast and the air mass will dry
out considerably. Likely some gusty north winds again through the
Santa Ynez range and the I5 Corridor through Saturday morning,
with some of that filtering down into the valleys. Temps Fri about
the same as Thu, though colder in the mountains and AV. Then
turning warmer Saturday (though still a few degrees below normal)
as the air mass starts to rebound and light offshore flow
develops.

.LONG TERM (SUN-WED)...21/142 PM.

A third trough will come through late Sat into Sun but this one
will be even farther east and its only impact will be to
strengthen offshore gradients and create some locally gusty
northeast winds and warmer temps. A fourth trough will drop south
along the coast of California Monday afternoon into early Tuesday.
Again minimal moisture to work with due to it`s unfavorable
trajectory but enough to give most of the area at least a threat
of light precip by Monday night. GFS ensembles match up pretty
well with the operational GFS with best chances again north of Pt
Conception, eastern LA County and the Grapevine area. MOS Guidance
favors similar temps Monday but with the strong onshore push ahead
of that night`s trough at least the immediate coast should see
some cooling Monday. Then several degrees of cooling Tuesday with
any rain chances ending during the afternoon as winds shift to
north and drying begins. Slightly warmer Wednesday post-trough and
with some light offshore flow.

&&

.AVIATION...22/0016Z.

At 00Z, the marine layer depth was around 1300 feet.

VFR conditions are expected through at least 10Z, then there is a
chance of MVFR conditions with light rain showers through the
remainder of the period. There is a chance that MVFR ceilings
could be 1000-1500 feet lower than forecast for some terminals.
There is a chance of moderate wind shear at KSBA through 08Z.
Moderate to strong wind shear and turbulence is possible at all
terminals after 20Z.

KLAX...VFR conditions are expected through at least 10Z. There is
a 30 percent chance of MVFR conditions between 10Z and 19Z
increasing to 50 percent chance after 19Z. There is a chance that
MVFR ceilings could be 1000-1500 feet lower than forecast for
some terminals. Moderate wind shear and turbulence is possible
after 20Z. Any east winds will remain less than 7 knots.

KBUR...VFR conditions are expected through at least 16Z. There is
a 30 percent chance of MVFR conditions between 16Z and 19Z
increasing to 50 percent chance after 19Z. There is a chance that
MVFR ceilings could be 1000-1500 feet lower than forecast for
some terminals. Moderate to strong wind shear and turbulence is
possible after 20Z. There is a 20 percent chance of cross winds
greater than 10 knots after 20Z.

&&

.MARINE...21/104 PM.

For the Outer Waters, high confidence in the current forecast.
There will be a short lull in the winds today and tonight. Winds
will likely increase to advisory levels again on Thursday. There
will be local Gale force gusts Thursday night. Small Craft
Advisory level winds will likely persist through Sunday.

For the Inner Waters, high confidence in current forecast. Winds
will be below Small Craft Advisory level today and tonight. Small
craft advisory level winds are likely on Thursday and Thursday
night with local gale force gusts across the western portions.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Frost Advisory in effect from 1 AM to 9 AM PST Thursday for
      zones 34>36. (See LAXNPWLOX).
PZ...NONE.

&&

.HAZARD POTENTIAL OUTLOOK (SAT-WED).

Gusty advisory level winds possible through the Santa Ynez Range
and the I5 corridor early Saturday. Low elevation snow possible
Monday night into Tuesday creating hazardous driving conditions in
the mountains, especially the I5 corridor area.

&&

$$

PUBLIC...MW
AVIATION...Hall
MARINE...Sweet
SYNOPSIS...Fisher

weather.gov/losangeles



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