Gale Warning 48, NWS Los Angeles, CA

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
112 PM PST Wed Dec 30 2020

.SYNOPSIS...30/854 AM.

Dry and warmer weather is expected through Friday along with
breezy north to northeast winds at times. A series of weather
systems will bring increasing chances of rain and mountain snow
late in the weekend into next week. High surf is expected along
the Central Coast through at least Friday.

&&

.SHORT TERM (TDY-SAT)...30/1249 PM.

Breezy northerly winds continuing today though subsiding a bit
this afternoon. Expecting another resurgence tonight into Thursday
as a weak trough passes through and models show enough upper
support and surface gradients to warrant a wind advisory for srn
SB County and the LA/Ventura mtns. May get a few hours of advisory
level winds in the western Antelope Valley as well later tonight
but will hold off on that for now. The northerly flow increase
tonight into Thursday will also be accompanied by some moisture
that may get enough of a lift on the north facing mountain slopes
to spawn a few light showers there Thursday. Snow levels will be
low enough to possibly get a dusting of snow over the Grapevine
and maybe an inch over the higher surrounding peaks but it
shouldn't pose significant travel concerns. Will run the wind
advisory until noon Thu as the typical late mid to late afternoon
onshore trend bring winds below advisory levels.

A second trough Thursday night into Friday will take an inland
trajectory and shift winds and gradients to northeast and create a
more traditional Santa Ana event. Should be a solid advisory
level wind event for LA/Ventura Counties with possibly some
isolated gusts to near 60 in the mountains Friday morning.
Offshore flow will warm areas near the coast but not much change
interior areas with some cold air lingering from the trough
passage offsetting the ridging aloft.

Saturday looks quiet with just some high clouds at times. Cooler
temps at the coast with onshore trends but warmer inland with weak
ridging aloft.

.LONG TERM (SUN-WED)...30/102 PM.

Another quiet day Sunday for the most part though some increasing
clouds and a chance of light rain for mainly western SLO County as
moisture and some warm advection arrive ahead of the next system.
Dry elsewhere through Sunday night. Some ECMWF ensemble solutions,
including the deterministic model are showing some very light
precip making it as far south as LA County Monday afternoon and a
farther south dip of the jet stream as the trough moves through.
Either way a very low impact event with higher snow levels than
with the previous systems.

Forecast gets murkier Tue and beyond as models are struggling
with the details which likely explains the relatively conservative
NBM pops. Chances are still very good that all areas will get
some additional precipitation by Wednesday evening but there's a
large spread of timing and strength possibilities. Some of the
solutions are showing a decent tap of moisture to the southwest
indicating a possible low end atmospheric river event, mainly just
northern areas but the 12z runs have scaled back on that
somewhat.

Another good chance of rain and mountain snow by around next
Friday as well.

&&

.AVIATION...30/1811Z.

At 1658Z, there was no marine layer at KLAX.

Generally high confidence in the current forecast. VFR conditions
are expected through the period. There is an outside chance of
LLWS and UDDFs through the period.

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

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

&&

.MARINE...30/1255 PM.

Low confidence in the current forecast. The greatest uncertainty
concerns the timing and exact placement of stronger winds.

Across the northern waters and south to San Nicolas Island and
west of the Channel Islands, seas will build and winds will
increase across the waters from tonight through Thursday evening.
There is a 60-70 percent chance of gales from early Thursday
morning through Thursday night, especially from Point Conception
south to San Nicolas Island. A large northwest swell is expected
to move into the waters tonight into Thursday, building to near
15 feet at 16 seconds by Thursday night. Another slightly larger
northwest swell will affect the waters Saturday and Sunday.

Inside the southern California bight, marginal offshore winds will
linger across the Santa Monica Bay this morning, then winds and
seas will increase across mainly the western portions of the bight
to SCA levels tonight through Thursday night. However, portions of
the bight neighboring the Santa Monica Mountains may also reach
SCA speeds/gusts. Winds are expected to shift to NNE by Friday
morning and bring another chance of SCA conditions nearshore from
Point Mugu to Santa Monica, and possibly from Newport Beach out to
near Catalina Island.

&&

.BEACHES...30/1255 PM.

A couple of large, fairly long period west to northwest swells
will push through the coastal waters through the weekend,
bringing high surf and dangerous rip currents to many west and
northwest facing beaches.

A High Surf Advisory remains in effect through Friday for the
northwest facing shoreline of the central coast. The breakers may
get close to warning criteria over the weekend.

A High Surf Advisory may be necessary for the Ventura County
beaches beginning Thursday and continuing through the weekend. At
this time, if an advisory becomes necessary by Thursday, the
range of wave heights would be from 4 to 7 feet. Even higher surf
becomes possible Friday and Saturday. The high surf is expected
to spread to the west facing beaches of Los Angeles County on
Friday or Saturday and continue through the weekend. Even west
facing beaches of the south coast of Santa Barbara will see
elevated surf of 3 to 6 feet. Dangerous rip currents are expected
and swimmers should remain out of the water. Be sure to stay off
rock walls and jetties. High surf may return to these areas as
early as Thursday with even larger surf possible over the weekend.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory in effect until 2 PM PST Friday for zones
      34-35. (See LAXCFWLOX).
     Wind Advisory in effect from 6 PM this evening to noon PST
      Thursday for zones 39-52>54. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PST Friday for
      zones 645-650. (See LAXMWWLOX).
     Small Craft Advisory in effect from 10 PM this evening to 3
      AM PST Friday for zone 655. (See LAXMWWLOX).
     Small Craft Advisory in effect until 9 AM PST Thursday for
      zone 670. (See LAXMWWLOX).
     Gale Watch in effect from Thursday morning through late
      Thursday night for zone 670. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PST Thursday for
      zones 673-676. (See LAXMWWLOX).
     Gale Watch in effect from late tonight through late Thursday
      night for zones 673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (SAT-WED).

Periods of moderate to locally heavy rain and mountain snow are
possible late Tuesday into Wednesday next week, creating hazards
to travelers.

&&

PUBLIC...MW
AVIATION...Sweet/Hall
MARINE...Sweet
BEACHES...Sweet
SYNOPSIS...MW

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