High Wind Warning 5, NWS Los Angeles, CA

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
952 AM PST Sun Jan 19 2025

.SYNOPSIS...19/346 AM.

Offshore flow will return today, with local northeast breezes,
less morning low clouds, and a few degrees of warming. Mostly
clear and locally breezy conditions are expected Sun night into
early Monday, then Santa Ana winds will increase during the day. A
moderate to strong Santa Ana wind event will likely affect
Ventura and Los Angeles Counties Monday night and Tuesday, with
weaker offshore flow continuing for much of next week.
Temperatures will be below normal Monday and Tuesday, with a
warming trend later next week. Humidity will be low to very low
most of next week. Frost or freezing temperatures are possible in
wind sheltered areas each night Monday through Thursday.

&&

.SHORT TERM (TDY-TUE)...19/911 AM.

***HIGH WIND WATCHES IN EFFECT LATE MONDAY AFTERNOON THROUGH
TUESDAY MORNING FOR MOST OF VENTURA COUNTY AND PORTIONS OF LOS
ANGELES COUNTY DUE TO A HIGH RISK OF WIDESPREAD DAMAGING WINDS***

***DANGEROUS FIRE WEATHER CONDITIONS EXPECTED FOR MUCH OF VENTURA
AND LOS ANGELES COUNTIES LATE MONDAY MORNING THROUGH TUESDAY
EVENING POSSIBLY CONTINUING THROUGH THURSDAY***

***UPDATE***

There is just a 1 mb onshore push to the east and a 1 mb offshore
push from north. The marine layer is 2000 ft deep and low clouds
cover most of the csts/vlys. Due to the diurnal onshore trends
forecast this afternoon clearing will be slow and a few beaches
may stay cloudy all day. It looks like there will be another
robust marine layer tonight. The deeper marine layer will keep max
temps a little cooler than fcst today.

Current wind forecast looks on track and the wind watches will
very likely be upgraded to wind warnings this afternoon.

forecast was updated to increase clouds and lower temps.

***From Previous Discussion***

A strong upper level ridge of high pressure in the eastern
Pacific will become even more amplified later today and tonight,
with the ridge axis extending well into British Columbia by late
tonight. Upper level flow will become northerly across the
western states later today and tonight. A short wave trough will
drop southward through Nevada and eastern CA tonight and early
Mon, carving out a positively tilted trough over Arizona and far
eastern CA on Monday. There are differences as to how far west the
developing trough will be, and this will affect where the best
height gradients, strongest winds aloft and best subsidence will
occur. The placement of the strongest upper level support will be
absolutely critical in determining how strong the upcoming Santa
Ana wind event will get, and what areas are most likely to receive
damaging winds. Unfortunately, at this time, confidence in these
details remains below average for this close to an event, mainly
because our most used computer models show subtle but important
differences with the upper levels pattern and support for winds.

The WRF shows the upper low digging slightly (but importantly)
farther west Monday and Mon night. For this reason, it shows more
in the way of upper level support, with stronger winds at 850 and
700 mb, better subsidence, and very strong cold air advection. It
also maintains upper support into early Tue afternoon. Winds at
850 mb on the WRF are forecast to reach 60 to 65 kt over portions
of L.A. and VTU Counties Mon night, with 55 kt winds up to 700 mb.
The GFS, which is similar to the EC, shows less digging with the
system, weaker flow aloft, and keep any upper support over the
region for shorter period of time.

At the surface, all models show a very strong an cold surface high
of around 1050 mb dropping into the central Rocky mountains Mon
night and early Tue. Surface pressure gradients between KLAX and
KDAG are forecast to peak around -9 mb offshore early Tuesday
morning according to the WRF and -6.5 to -7.5 according to the GFS
and EC.

It does appears that a Santa Ana wind event will unfold fairly
rapidly Mon, beginning in the mtns of L.A. County in the afternoon,
then working into the valleys and to coastal areas in the evening
or early Mon night. While most of VTU County, the mtns and most
valley areas of L.A. County, and the Malibu Coast are likely to
have a period of at High Wind Warning level winds (or at least
close to warning level winds) late Mon into Tue, there remains
uncertainty as to the magnitude and placement of the strongest
winds. Also uncertain is whether or not mountain wave activity
will force damaging winds down into the foothills of the San
Gabriel Valley and the northeastern San Fernando Valley Mon
evening through early Tue. The WRF suggests it is a distinct
and dangerous possibility, while the mid and upper pattern shown
by the GFS and EC is not as favorable. Will let the next shift
look at the 12Z model runs to see if they provide more clarity.

Widespread northeast wind gusts of 60 to 80 mph are likely (70-80%
chance) in the mountains/foothills of L.A./Ventura counties, with
the potential for isolated gusts in the 80-100 mph range across
the most favored mountain areas. For now, that appears to be the
San Gabriel mountains, Santa Susana mountains, southern Ventura
mountains near the Highway 126 corridor, and the western Santa
Monicas. For the valleys of L.A./VTU Counties, the VTU County
coast, and the Malibu Coast (especially western sections, peak
gusts of 50-70 mph are most likely.

With the potential for mountain wave induced winds, it is
important to note that there could be locally higher gusts than
advertised in foothill and elevated valley communities near the
Highways 118 and 210 corridors extending from Simi Valley/Moorpark
eastward into the northern San Fernando Valley, and the foothills
of the San Gabriel Valley. If the upper level support is closer
to that indicated by the WRF, even typical wind sheltered areas of
the LA Basin and the San Gabriel Valley floor could see some
gusty winds at times (mostly in the 30-50 mph range).

DUE TO THE STRONG WINDS AND VERY LOW RELATIVE HUMIDITY VALUES,
DANGEROUS HIGH END RED FLAG FIRE WEATHER CONDITIONS ARE EXPECTED
LATE MONDAY MORNING THROUGH TUESDAY EVENING. NEW OR EXISTING FIRE
IGNITIONS WILL HAVE A HIGH RISK FOR VERY RAPID FIRE SPREAD AND
EXTREME FIRE BEHAVIOR WITH LONG RANGE SPOTTING. Please refer to
our Fire Weather products (RFWLOX) and the Fire Weather discussion
below for additional details.

.LONG TERM (WED-SAT)...19/601 AM.

An upper ridge in the eastern Pacific will move into the West
Coast Wed and hold in place thru Thu. Low level gradients will
remain offshore, with gusty and possibly advisory level winds at
times across L.A./VTU Counties. There will be significant warming
Wed, with additional warming Thu. Max temps could reach or exceed
80 degrees in some of the warmest valley and inland coastal plain
locations Thu. Very dry and occasionally windy conditions will
likely bring continued significant fire weather concerns to
L.A./VTU Counties thru at least Thu. Due to the very dry and clear
conditions, it will get very cold in wind sheltered interior
locations each night Tue night thru Thu night. The coldest night
will likely be Tue night, and temps could drop into the mid teens
in the Antelope Valley. The may be freezing temps in coastal
sections of SLO/SBA Counties, and the valleys of L.A./VTU Counties.

It continues to be a low confidence forecast for Fri and Sat. An
upper low will bring a 20-30 percent chance of fairly widespread
and mainly light rain and mountain snow with the potential for low
snow levels by Sat. There is a 10 percent chance of a thunderstorm
should the associated upper low pass close to our area. This
would increase the threat for localized heavier rainfall. There is
also a 30-40 percent chance that the system will pass far enough
to the east for no rain across most of the region. Either way a
cool down is likely next weekend with breezy conditions,
especially in the interior.

&&

.AVIATION...19/1213Z.

At 07Z at KLAX, there was no marine layer nor an inversion.

Overall, moderate confidence in 12Z TAF Package. Highest
confidence for desert airfields and moderate confidence for
remaining TAF sites. Timing of Cigs/vsby restrictions may be off
+/- 2 hours. Flight cats could be off one or two especially during
worst conditions.

There is a 30% chance of IFR conds or lower at KSMX from 00Z to
12Z Mon. Similar chances for MVFR conds at KSBA from 06Z to 12Z
Mon. There is a 20% chance of LIFR conds at KSBP thru 18Z Sun.

KLAX...Moderate confidence in 12Z TAF. Timing of flight cat
changes may be off by up to +/- 2 hours. There is a 10% chance of
BKN/OVC005-010 IFR conds from thru 18Z Sun. Good confidence that
any east wind component remains below 8 kt thru the fcst pd.

KBUR...Moderate to high confidence in 12Z TAF. There is a 10%
chance of ~BKN/OVC015-025 thru 18Z Sun.

&&

.MARINE...19/220 AM.

For the Outer Waters, Small Craft Advisory (SCA) level winds are
likely (80-90% chance) Sunday afternoon/eve thru Monday morning.
These conditions will be favored from Point Conception to San
Nicolas Island which includes the waters around and to the west of
the Channel Islands (PZZ676/673). There is a 40-50% chance of
GALE FORCE level NE winds for the waters around and to the south
of the Channel Islands (PZZ676) late Monday night thru Tuesday
morning. Otherwise, sub-advisory conds are expected thru Thursday
night.

For the Inner Waters North of Pt Sal (PZZ645), there is a 30%
chance of SCA level wind gusts Sunday afternoon/eve just offshore
of Port San Luis and Sam Simeon Point. Otherwise, sub-advisory
conds are expected thru late in the week.

For the Inner Waters South of Point Conception, there is a 40-50%
chance of SCA level wind gusts for far western portions of the
Santa Barbara Channel Sunday afternoon thru late evening. From
Ventura Harbor to Santa Monica and out past the Channel Islands,
there is a 60-70% chance of GALE FORCE E/NE wind gusts late Monday
afternoon through Tuesday morning. For the nearshore waters from
Channel Islands Harbor to Malibu and out to Santa Cruz Island,
there is a 20% chance of STORM FORCE wind gusts Monday night into
Tuesday morning. From the Orange County shores through the San
Pedro Channel, there is a 40-50% chance of GALE FORCE wind gusts
Monday evening through Tuesday morning. There is a 60-70% chance
of 25-30 kt winds impacting Avalon Harbor. Steep, choppy seas of 5
to 8 feet will be possible during this time frame.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Wind Watch remains in effect from Monday afternoon
      through Tuesday morning for zones
      88-354-355-358-362-369-371-372-374>380. (See LAXNPWLOX).
     High Wind Watch in effect from Monday afternoon through
      Tuesday morning for zones 373-548. (See LAXNPWLOX).
     Red Flag Warning in effect from 10 AM Monday to 10 PM PST
      Tuesday for zones 288-354-355-358-362-369>380-548. (See LAXRFWLOX).
     Fire Weather Watch in effect from Tuesday evening through
      Thursday evening for zones 288-354-355-358-362-369>380. (See LAXRFWLOX).
PZ...Gale Watch in effect from Monday afternoon through Tuesday
      morning for zones 650-655-676. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 PM this afternoon to 9
      AM PST Monday for zones 673-676. (See LAXMWWLOX).

&&

PUBLIC...DB/RM/Rorke
AVIATION...Black
MARINE...Smith/Black
SYNOPSIS...DB/RM/DMB

weather.gov/losangeles

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