LA Area Forecast Discussion

000
FXUS66 KLOX 310106
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
506 PM PST Mon Jan 30 2023

.SYNOPSIS...30/244 PM.

Rain and mountain snow showers will taper off this evening. Gusty
Santa Ana winds will affect wind prone areas tonight through
Wednesday, strongest on Tuesday. Near to below freezing
temperatures expected each morning through Thursday, coldest on
Wednesday. Daytime temperatures will increase through Wednesday or
Thursday, but remain below normal. Light rain possible north of
Santa Barbara Friday, then again Saturday night into Sunday. Gusty
north winds possible Monday and Tuesday next week.

&&

.SHORT TERM (TDY-THU)...30/156 PM.

A closed and cold upper level low pressure system, currently
centered about 200 miles south-southeast of Santa Barbara, will
continue to push toward the southeast and into northern Baja by
Tuesday morning. As this system pushes further to the south, it
will carry the shower activity along with it and out of the area
by later this evening. Until then, slightly unstable air currently
getting into Orange County will push northward and likely bring
additional showers into the early evening, especially over Los
Angeles County and the waters up to Santa Barbara. Any of these
showers may bring 5 to 10 minutes of brief heavy rain, small hail,
and even a lightning strike. With snow levels still in the 3,500
foot neighborhood, brief heavy snow showers are also possible
mainly over the Los Angeles County Mountains. Slippery roads for
the afternoon commute should be expected, especially over Los
Angeles County. Will keep the Winter Weather Advisory going over
the interior Los Angeles County Mountains, but end the other
advisories as the threat for impactful snow accumulations is on
the decline everywhere else. The threat for the I-5 Tejon Pass
is still present through the early evening, but it too is on the
decline.

As the focus on precipitation decreases, the focus will turn to
the wind and cold. Northeast winds are already forming thanks to
strengthen winds aloft (due to the position of our current storm
system), and the healthy -7 offshore millibar trend over the last
24 hours. These trends will increase tonight into Tuesday, setting
up a moderate Santa Ana wind event. Ensemble solutions have locked
into an event of the peak gusts to 30 to 50 mph variety over most
of Los Angeles and Ventura Counties, while weaker but still breezy
winds will continue over the SLO coast and hills tonight. This
will dry us out quickly, and push daytime temperatures into the
60s south and west of the mountains. Would expect a few extra
power outages and a weakly rooted tree or two to come down. These
winds will weaken by around 10 mph Tuesday Night and Wednesday.

A cold air mass will linger behind our system, and with fast
drying due to the offshore flow, night-time / early morning
temperatures will be downright frigid. Wednesday looks to be the
coldest, with the best combination of clear skies, dry air, and
less wind. Interior valleys and mountains will be the coldest,
with lows commonly in the 20 to 30 degree range. This includes
the Antelope Valley, which could dip below 20 degrees for several
hours Tuesday morning (20% chance) or Wednesday morning (50%
chance). A Hard Freeze Watch will be issued for Wednesday morning.
The other interior areas should stay above 20 and since they all
have already had more than 2 freeze events, will not be considered
for any frost freeze hazards. On the coastal side of the
mountains, several areas will be flirting with freezing
temperatures. The Central Coast and area around Ojai have the best
chances, and a Frost Advisory and Freeze Watch will also be
issued to cover that. More areas will likely need frost advisories
for Wednesday morning.

Early morning temperatures will remain cold but improved on
Thursday as a narrow high pressure ridge forms aloft. This should
bring temperatures up to almost normal away from the beaches.

.LONG TERM (FRI-MON)...30/217 PM.

The majority of projections are showing a trough of low pressure
pushing into northern California early Friday, with a cold front
pushing down the coast. By all indications, this front will
dissipate somewhere over southwest California. As such, the
potential for any rain decreases drastically further to the south.
Taking the hint from the various ensemble models (EPS GEFS CCMC),
those chances decrease quickly from San Luis Obispo County (50
percent) to Los Angeles County (10 percent). The most likely
scenario keeps any rain north of Santa Barbara. If rain
materializes, it will be light, with only a 10 percent chance of
reaching 0.50 inches for San Luis Obispo. Another weak system
looks to impact the area in a similar way Saturday night through
Sunday, with any rain likely staying north of Santa Barbara.
Between those two systems, weak offshore flow is possible on
Saturday with a narrow ridge aloft. As a result, Friday through
Sunday looks rather mild temperature-wise.

Fairly high confidence of gusty north winds forming Sunday Night
through Tuesday (70 percent chance of gusts over 35 mph in the
mountains). Initially, lingering moisture may bring light showers
to the north mountain slopes Sunday Night through Monday morning.
Otherwise it should be clear and dry. Temperatures are very
uncertainly however. The ECMWF ensemble 500 millibar heights give
a great picture of that, with the range of possible outcomes
between 550 decameters (cold) and 575 decameters (sort of warm).
We will have to see what shakes out.

&&

.AVIATION...31/0106Z.

At 0005Z at KLAX, there was no marine layer nor a sfc based
inversion.

Good confidence in Cig/Vis fcst (LA county sites may hold on to
the VFR cigs for a few hours longer than fcst). Moderate
confidence in wind fcsts. NE winds may start 2 hours earlier than
fcst. KLAX and KSMO may get 5 kt NE wind 11Z-18Z.

Gusty winds may create UDDFS, lgt-ocnl mdt turbc and LLWS 12Z-18Z.

KLAX...Good confidence in TAF. There is a 40 percent chc of
06006kt winds 11Z-18Z.

KBUR...Good confidence in Cig/Vis fcst (SCT conds may not arrive
until 09Z) There is a 30 percent chc of 06025g35kt winds 13Z-18Z.

&&

.MARINE...30/144 PM.

For the Outer Waters, moderate to high confidence in current
forecast. For PZZ670/673, high confidence in winds and seas
remaining below Small Craft Advisory (SCA) levels today through
Friday. For PZZ676, high confidence in winds and seas remaining
below SCA levels through tonight. On Tuesday, there is a 50%
chance of SCA level northeast winds. For Tuesday night through
Friday, high confidence in winds and seas remaining below SCA
levels.

For the Inner Waters north of Point Sal, high confidence in
current forecast. Winds and seas will remain below SCA levels
today through Friday.

For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. For tonight through Tuesday
morning, there is a 70% chance of SCA level easterly winds from
Ventura south to Santa Monica. Therefore, a SCA has been issued
for the inner nearshore waters from Ventura to Santa Monica.
Otherwise, winds and seas are expected to remain below SCA levels
through Friday.

There is a 50-60 percent chance of gusty winds reaching the front
side of Avalon Harbor between 3 am and 10 am Tuesday. The winds
are expected to reach 15 to 25 knots with 3 to 5 foot wind waves.

There is the possibility of isolated thunderstorms today across
the coastal waters south and east of the Channel Islands. Any
thunderstorms that develop will produce brief gusty winds, rough
seas, small hail and dangerous cloud to surface lightning.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 6 PM PST Tuesday for zones
      53-54-88-358-359-363-547. (See LAXNPWLOX).
     Winter Weather Advisory in effect until 8 PM PST this evening
      for zone 54. (See LAXWSWLOX).
     Hard Freeze Watch in effect from late Tuesday night through
      Wednesday morning for zone 59. (See LAXNPWLOX).
     Frost Advisory in effect from 1 AM to 8 AM PST Tuesday for
      zones 340-341-346-347-356-357. (See LAXNPWLOX).
     Freeze Watch in effect from late Tuesday night through
      Wednesday morning for zones 340-341-346-347-356-357. (See LAXNPWLOX).
     Wind Advisory in effect from 3 AM to 6 PM PST Tuesday for
      zones 354-355-362. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect from 10 PM this evening to 9
      AM PST Tuesday for zones 650-655. (See LAXMWWLOX).

&&

$$

PUBLIC...Kittell
AVIATION...Rorke
MARINE...Sweet/RAT
SYNOPSIS...RK

weather.gov/losangeles

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

NWS LOX Office Area Forecast Discussion