Area Forecast Discussion
Issued by NWS Los Angeles, CA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS66 KLOX 220613
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1013 PM PST Mon Jan 21 2019

.SYNOPSIS...21/954 PM.

Gusty offshore winds will continue through Wednesday across many
mountain and valley areas and will be strongest during the morning
hours. Temperatures will gradually warm through the week as
conditions remain dry.

&&

.SHORT TERM (MON-THU)...21/835 PM.

Vigorous upper level trough digging into Arizona this evening,
bringing strong upper level northerly wind support to Southwest
California. Latest NAM model showing a strong 100-110 knot core
at 500 mb level, with even wind of 45-55 knots being detected at
700 mb level. While north-south offshore pressure gradients are
only moderate tonight, this wind event being driven by the
strong upper level wind support and cold air. Winds advisories
in effect for many areas south of Point Conception with this
northerly wind event. The strongest winds will be focused across
the mountains (especially I-5 corridor and Santa Ynez mountains)
where gusts of 50 to 60 mph will occur, with isolated gusts
over 60 mph in favored mountain and foothill locations, such as
Whitaker Peak and Montecito Hills. For coast and valley areas,
will continue to see wind gusts between 35 and 50 mph, with some
of the strongest winds currently focused across the Santa Clarita
Valley, San Fernando Valley, foothills of the San Gabriel Valley,
and Los Angeles Coast (especially Malibu to Hollywood Hills and
405 corridor through west Los Angeles). The gusty north winds will
peak this evening before shifting to the northeast after
midnight. The most significant wind impacts include the continued
potential for downed trees and powerlines, power outages, and
northerly cross winds at LAX.

There will continue to be some residual clouds and isolated snow
showers on the north facing mountain slopes tonight. As the winds
shift to the northeast later tonight into Tuesday, there will
continue to be fairly strong upper level wind support (up to 50
knots at 850 mb level) along with cold air advection. Once again,
the low level offshore gradient will be fairly modest, likely
peaking in the -4 to -5 mb range on Tuesday morning. At this
point, winds will mainly be focused across typical northeast
facing passes and canyons of Los Angeles and Ventura counties,
with gusts in the 50-60 mph range across the mountains, and 35-50
mph for coastal/valley areas. Once again, would not be surprised
to see a couple favorable locations in the LA county mountains and
adjacent foothills have gusts over 60 mph on Tuesday morning.
Temperatures will mostly remain the mid to upper 60s with
Tuesday`s offshore wind event, then warm into the lower to mid 70s
by Wednesday as upper level ridge of high pressure builds over
the region.

*** From previous discussion ***

It will be warmest on Thursday with above normal temps just about
everywhere thanks to offshore flow and warming at 850 mb and in
the boundary layer. Look for highs in the warmest vlys and inland
coastal areas to reach the mid to upper 60s on Tue, the upper 60s
to lower 70s on Wed, and generally in the 70s to near 80 on Thu.
Low temps will also be quite cool the next couple of nights with
the coldest sheltered vlys dropping to near or slightly above
freezing. However, widespread frost is likely for the SLO County
interior vlys, with freezing conditions in the mid to upper 20s
expected for the Antelope Vly.

.LONG TERM (FRI-MON)...21/205 PM.

The EC and GFS are in generally good agreement with the synoptic
features over the ern Pac to western U.S. for Fri thru Sun. On Mon,
the EC dives an upper level trof deep into the Great Basin, with
srn CA under a broad northerly flow aloft and lowering 500 mb
heights. The GFS, however, keeps weakening upper level ridging
over CA Sun night and Mon. Will lean more toward the GFS for Mon,
with milder temps continuing. At any rate, both the EC and GFS
bring dry weather to the forecast area thru the extended period.

Gusty offshore winds night and morning hours can be expected across
swrn CA Fri and Sat, with gusts possibly reaching advisory levels in
the wind-prone areas. Weaker offshore flow can be expected into Sun,
with a transition to some onshore flow on Mon. Mostly clear skies
will prevail across the region Fri thru Sun, then some mid and hi
level clouds could move in for Mon with partly cloudy skies as a
whole.

Temps are forecast to be several degrees above normal for many areas
Fri thru Sun, with the warmest day on Sat. Temps for Mon should drop
to near normal for the most part. Highs in the warmest vlys and
inland coastal areas should reach the mid 70s to near 80 on Fri,
upper 70s to low 80s on Sat, lower to mid 70s on Sun, and upper 60s
to low 70s on Mon.

&&

.AVIATION...22/0606Z.

At 0540Z at KLAX, there was no marine layer nor a sfc based
inversion.

Moderate confidence in 00Z TAF package. High confidence in VFR
sky conditions for all sites through the TAF period. Low to
moderate confidence in wind forecast due to some uncertainty of
the timing of changes in strength/direction. With strong upper
level wind support tonight through Tuesday morning, there will be
the potential for strong uddfs and llws for TAF sites south of
Point Conception.

KLAX...High confidence in CAVU conds through the period. Good
confidence that there will be no X-winds or east wind component
greater than 8 kt, however there is possibility of LLWS 12Z-20Z.

KBUR...High confidence in CAVU conds through the period. Moderate
confidence in timing of changes in wind strength/direction.
Northwest-north winds likely gusting between 20 and 30 knots
through tonight, shifting to the northeast on Tuesday morning.
There is the potential for strong uddfs and LLWS through 22Z.

&&

.MARINE...21/822 PM.

For the Outer Waters, moderate confidence in current forecast.
Strong Small Craft Advisory (SCA) level northwest winds will
continue through tonight over the northern waters, with local gale
force gusts over the two southern zones PZZ673-676. There is a 30%
chance the gales will become more widespread through late tonight. On
Tuesday, there is a 30% chance of SCA level winds, except a 60%
chance over PZZ676. Then winds and seas are expected to remain
below SCA levels Wednesday through Saturday.

For the Inner Waters north of Point Sal, high confidence in
current forecast. SCA level northwest winds will continue through
tonight. For Tuesday through Saturday, winds and seas are
expected to remain below SCA levels.

For the Inner Waters south of Point Conception, moderate
confidence in current forecast with gusty N to NE winds developing
overnight into Tuesday. SCA conditions are expected south of
Ventura, and especially from Point Mugu to Santa Monica where
local gale force gusts will be possible, and south of Palos Verdes
where gusts to 30 kt will be possible. The NE winds will diminish
some late Tuesday afternoon and evening, but will likely strengthen
again late Tuesday evening through Wednesday morning. While the
winds on Wednesday are expected to be slightly weaker, they should
still meet SCA criteria. Seas will be hazardous, building to

&&

.BEACHES...21/805 PM.

A westerly swell will produce moderate to elevated surf and
strong rip currents on west-facing beaches through Tuesday. Large
astronomical high tides are also be expected through Tuesday
morning. Due to the higher than normal tides and the surf, there
could be minor coastal flooding near the time of the morning high
tide around 10 AM on Tuesday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement in effect through Tuesday morning for
      zones 34-35-40-41-87. (See LAXCFWLOX).
     Wind Advisory in effect until 10 AM PST Tuesday for zones
      39-52. (See LAXNPWLOX).
     Wind Advisory in effect until noon PST Wednesday for zones
      41-44>46-53-54-88-547. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PST Tuesday for
      zones 645-670-673-676. (See LAXMWWLOX).
     Small Craft Advisory in effect until 1 PM PST Tuesday for
      zones 650-655. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (THU-MON).

Advisory level north to northeast winds will be possible night
and morning hours Thursday and Friday for wind-prone areas of
Ventura and Los Angeles Counties.

&&

$$

PUBLIC...Gomberg/Sirard
AVIATION...Rorke
MARINE...Smith
BEACHES...Smith
SYNOPSIS...Kj

weather.gov/losangeles


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.