Frost Advisory 2, NWS Los Angeles, CA

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1002 PM PST Wed Jan 2 2019

.SYNOPSIS...02/358 PM.

Gusty Santa Ana winds and offshore flow will keep the region dry
through Friday. A Pacific storm system is expected to move over
Southwest California between late Friday and Monday and likely
bring rain and mountain snow to the region along with periods of
gusty winds.

&&

.SHORT TERM (WED-SAT)...02/827 PM.

Cold upper level low pressure system has now shifted well eastward
into New Mexico this evening, while an upper level ridge of high
pressure builds in from the west. Still have some offshore flow
near the surface as evident by the -3.2 mb gradient between LAX-
Daggett but much less upper level wind support from this time
yesterday evening. The LAX-Daggett gradient is expected to climb
to around -4.5 mb which will maintain offshore breezes across the
mountains of LA/Ventura counties through Thursday morning, with
gusts generally in the 25-35 mph range.

Still a chilly air mass in place across the region tonight but
has moderated a bit from last night. However, with dry air in
place and weaker winds, do expect another round of chilly
overnight lows, but generally a few degrees warmer than last
night. Still have freeze warnings in effect for the Ojai Valley
and Central Coast for later tonight. Temperatures on Thursday
are expected to be a few degrees warmer with building heights,
with little change into Friday.

*** From previous discussion ***

Friday will begin with more warming and increasing cloudiness but
the ridging aloft will break down later on Friday as a developing
storm system over the west- central Pacific Ocean will move
across the eastern Pacific Ocean through late week.

The storm, currently just a wave northwest of Honolulu, will
develop into a cut-off trough between Friday and Saturday off the
West Coast. Afternoon high temperatures will be near normal on
Friday.

Saturday will see the effects of the storm system reaching into
our area, beginning in SLO County and then moving fairly quickly
down the coast. Southerly flow and ample moisture should make this
a good rain producer for our area.  Model solutions are
advertising around 1-1.5 inches of rainfall with the storm
system, but there is still a fairly large spread in ensemble
solutions between several hundredths and 2 inches. QPFs fall
inline with CNRFC and WPC guidance for now. Snow should start
around 5500' but the move higher during the event.

.LONG TERM (SUN-WED)...02/127 PM.

The storm system should be through the area by Sunday evening,
with colder than normal temperatures expected. The synoptic
pattern moves to a more neutral condition Monday and a brief
period of ridging on Tuesday will bring temperatures back up to
normal before another Pacific storm system could move into the
area on Wednesday/Thursday.

&&

.AVIATION...03/0601Z.

At 06Z, there was no marine inversion at KLAX.

VFR conditions are expected through the period. No wind impacts
are expected at this time.

KLAX...VFR conditions are expected through the period. Any east
winds should remain less than 7 knots.

KBUR...VFR conditions are expected through the period. No wind
impacts are expected at this time.

&&

.MARINE...02/827 PM.

Moderate to high confidence in the current forecast. Winds and
seas are expected to remain below Small Craft Advisory (SCA)
levels through Friday. An approaching cold front will bring
increasing southerly winds to the Coastal Waters Friday night
through Saturday, and winds will remain gusty as they shift to
the northwest late Saturday night into Sunday.

For the northern waters, including the nearshore waters north of
Point Sal, there is a 60% chance of SCA conditions developing
Friday night and continuing through Sunday. The gusty south winds
will spread over the southern waters Saturday. The Southern Outer
Waters (PZZ676) will see SCA conditions through Sunday, while the
nearshore waters south of Point Conception will see SCA winds
Saturday through Saturday evening.

A moderate period WNW swell will move into the waters Friday night
into Saturday, building to 15-19 feet at 13-15 seconds over the
outer waters and PZZ645 Saturday night. Seas of 6-10 feet will be
possible over the nearshore waters in the SoCal bight. The seas
will gradually diminish through Sunday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Freeze Warning in effect until 9 AM PST Thursday for zones
      35-44. (See LAXNPWLOX).
PZ...NONE.

&&

.HAZARD POTENTIAL OUTLOOK (SAT-WED).

A storm system will likely bring rain and mountain snow to the
region late Friday night through Monday. Gusty southerly winds
with the storm system could develop between Friday and Saturday.

&&

PUBLIC...Gomberg/jld
AVIATION...Hall
MARINE...Smith
SYNOPSIS...Smith

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