Storm Warning 1, NWS Los Angeles, CA

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
951 AM PST Mon Jan 6 2025

.SYNOPSIS...05/356 PM.

Quiet weather is expected through Monday with warm and dry
conditions, then a major north to northeast wind event will
develop Tuesday. The winds will peak on Wednesday and continue
into Thursday with widespread damaging winds and critical fire
weather conditions. Residents should look for updates about this
event over the next few days.

&&

.SHORT TERM (TDY-WED)...06/819 AM.

***UPDATE***

Latest satellite and surface observations indicate mostly clear
skies across the area. Some north to northeast winds, gusting
30-40 MPH, are observed across the mountains.

Forecast-wise for the immediate short term, no significant issues
are anticipated. Skies will remain mostly clear through this
evening with only some scattered cirrus clouds. As for winds,
winds should generally exhibit a diurnal trend with weak onshore
winds developing this afternoon, before the winds start turning
back offshore this evening. Speeds are expected to remain below
advisory levels. As for temperatures, interior sections will be a
few degrees warmer today, but some slight cooling will be observed
west of the mountains.

Overall, current forecast has good handle on the immediate short
term. So, no significant updates are expected. For the afternoon
forecast suite, attention remain on a strong offshore wind event
Tuesday through Thursday.

***From Previous Discussion***

***STRONG AND DAMAGING WINDS WITH DANGEROUS FIRE WEATHER
   CONDITIONS FOR PORTIONS OF VENTURA AND LOS ANGELES COUNTIES
   TUESDAY THROUGH THURSDAY***

Today will be the calm before the storm (windstorm). NW flow
covers the state. An impulse is just starting to work its way into
the north of the state. Offshore flow continues and is between 3
and 5 mbs offshore from both the N and E. Sub advisory gusts are
occuring below passes and canyons. Look for mostly sunny conditions
today. Max temps will be in the 60s at the beaches but in the 70s
for the rest of the csts/vlys.

A dangerous offshore wind event will start to develop tonight. A
high amplitude ridge will push into Oregon and will help develop a
sharp pos tilt trof extending from Utah to Las Vegas. in between
these two features will be a stream of fast moving NE to SW winds
that will be right over Srn CA. Offshore flow at the sfc will
increase by a mb or two. While the sfc flow is only moderate the
amount of NE winds aloft coupled with a grip of cold air advection
will set the stage for a major wind event.

Advisory level NE winds will develop in the mtns around midnight
tonight and will then work their way into the western LA vlys and
eastern VTA vlys and then reaching the western Santa Monica mtn
Malibu area around dawn. Warning level gusts will then become
possible during the morning diurnal peak.

After a short lived dip in wind speeds Tuesday afternoon the winds
will accelerate to dangerous levels. The river of fast moving air
(60 mph at 700 mb) will shift to the south and will be directly
over LA and VTA counties. Offshore sfc flow will increase to
between 6 and 7 mbs form both the N and E. Warning level wind gusts
from 60 to 80 mph (some ridgetops may see 90+ mph) will develop
Tuesday evening and will spread through the western LA vlys and
eastern VTA vlys over the Santa Monica mtns and out through
Malibu. There may be some slight adjustments to the location of
the strongest axis of winds and there is a chance the winds will
be a little more northerly with the strongest winds a little more
to the east than fcst.

Of particular note is the possibility of the creation of strong
breaking mtn waves. These occur when very strong winds aloft
intercept mountain tops at nearly perpendicular angles which will
happen with these events. These short lived and very difficult to
predict events can cause considerable local damage wherever they
occur. The most likely areas for this phenomena are the eastern
San Fernando Vly and the northern San Gabriel Vly.

HIGH WIND WARNINGS have been issued for LA county to include the
mountains (including the Santa Monicas), San Fernando/San
Gabriel/Santa Clarita Valleys and the Calabasas area from 1000 AM
Tuesday through 600 PM Wednesday. In VTA county HIGH WIND WARNINGS
have been issued for the southeastern valleys and the Santa
Susana Mountains for the same time period. Given the of the
exact location of the wind axis High Wind Watches cover most of
the rest of LA and VTA counties and will either be converted to
warnings or advisories as the event draws nearer. Please see the
product LAXNPWLOX for all of the details on the wind warnings and
advisories.

The offshore flow will affect SLO and SBA counties as well, but
will not be nearly as strong. Advisory level gusts are likely for
the mtn areas but the csts/vlys there will likely only see sub
advisory gusts.

Humidities will drop as well, esp on Wednesday, and this will
create dangerous fire weather conditions. Please see the fire
weather discussion below for more details.

Residents across Southern California are urged to remain vigilant
and monitor the latest forecasts. There is high confidence in
strong offshore winds with the potential to be the strongest wind
event of the season, especially for the Southland valleys. Trees,
large tree branches, and power lines may be downed by the wind
next week. Residents living the near the foothills and mountains
are advised to review the Ready,Set,Go! fire plan. Most residents
should be in the Set stage and being prepared to go in the event
of the fire evacuation.

Max temperatures will be interesting with this event. There will
be so much cold air advection Tuesday that it will totally
overwhelm the usual compressional heating that occurs with Santa
Ana winds. Max temps Tuesday will cool 5 to 10 degrees across the
board. On Wednesday there will be much less cold air advection and
max temps will rise by about the same 5 to 10 degrees.

Overnight lows Wednesday night will be very cold in wind sheltered
locations with clear skies, dry air and a cool airmass.

.LONG TERM (THU-SUN)...06/1214 AM.

There is good agreement with the deterministic mdls and the
ensemble means, which mean that there is better than average
confidence in the xtnd fcst.

On Thursday the offshore event will continue, but in a reduced
form. The upper support is still atop of the southern portion of
the state, but the offshore sfc gradients are only half as
strong. There will likely be advisory level gusts across most of
the LA mtns with a slightly less chc in the LA vlys (except for
the San Gabriel) and Santa Monicas. Max temps will mostly be in
the 70s across the csts and vlys. RHs will remain low and the fire
danger will continue through the day.

The upper support continues to weaken on Friday as does the sfc
offshore flow. There will be still be winds through and below
passes and canyons in the morning, but they will be under advisory
levels. The E Pac ridge will nose further into the state and hgts
will climb to 580 dam. The weaker offshore flow will allow a
stronger seabreeze to bring 2 to 4 degrees of cooling to the csts
and lower vlys, while the higher hgts will warm the rest of the
area by the same 2 to 4 degrees.

The ridge will be knocked down by a fast moving trof the will zip
down the CA/NV border. Hgts will collapse to 572 dam. The offshore
flow from the east will reverse to onshore. All of this will
combine to bring 4 to 6 degrees of cooling to most of the area
save for the Antelope Vly where the temps will not change much.

Dry NW flow will set up over the state on Sunday. There will not
be much weather to speak of. Max temps will not change much from
Saturday's values.

Both the EC and GFS both show another possible mdt-stg offshore
event sometime during the 10th through the 12th time period.
Looking even further ahead both the 360 hour runs of the GFS and
EC do not show any rain all the way through the 20th of the month.

&&

.AVIATION...06/1750Z.

At 17Z at KLAX, there was a surface based inversion up to 1600
feet with a maximum temperature of 18 C.

Overall, moderate to high confidence in 18z TAF package. There is
a 10-20% chance of MVFR conds at KSBP after 10Z. Timing of
cigs/vsby restrictions may be off +/- 2 hours and Flight cats
could be off one or two. Timing of wind shifts may be off an hour
or two. Wind gusts may be off +/- 5 kts for KSMX, KBUR, KVNY, and
desert airfields.

After 06Z Tue, LLWS and moderate turbulence will be possible due
to strong N-NE winds over the mtns of LA and Ventura Counties,
especially for KVNY, KBUR, KCMA, KOXR, KSMO, KPMD, and KWJF.

KLAX...Moderate confidence in 18Z TAF. There is a 30% of cigs
<OVC005 from 06Z-15Z. Significant LLWS likely between 12Z-18Z.
There is a 20% chance of an east wind component reaching 6-8 kt
after 06Z.

KBUR...Moderate to high confidence in 18Z TAF, lower confidence
in winds speeds after 10Z Tue.

&&

.MARINE...06/816 AM.

For the Outer Waters, Small Craft Advisory (SCA) level wind
and/or seas are expected to occur much of the time through Tuesday
night. South of the Channel Islands (PZZ676) there is a 70-80%
chance of SCA level NE winds in eastern portion Tuesday night
through Wednesday.

For the Inner Waters north of Point Sal, SCA northeast winds are
likely through this morning, especially for the nearshore waters.
Low confidence in winds there on after, with chance of SCA
northeast winds continuing through at least Wednesday.

For the Santa Barbara Channel, there is a 80% chance of SCA level
NW winds across the western portion of PZZ650 this afternoon thru
Tuesday morning. Moderate to high confidence in Santa Ana winds
impacting eastern portions of the SBA channel Tuesday through
Wednesday.

A strong Santa Ana event is likely tonight through Friday
morning. The peak and most expansive period is expected Tuesday
through Wednesday which has warranted a GALE Watch for the
southern inner waters. Latest guidance suggests these potential
GALES may extend out to PZZ676. At this time, the strongest winds
(GALES) appear to be in favored areas nearshore from Point Mugu
to Santa Monica, with a moderate risk for Catalina Island.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Wind Warning remains in effect from 10 AM Tuesday to 6
      PM PST Wednesday for zones 88-369>375-378>380-548. (See LAXNPWLOX).
     High Surf Advisory in effect until 9 PM PST Tuesday for zones
      340-346. (See LAXCFWLOX).
     High Surf Advisory in effect from 9 PM this evening to 9 PM
      PST Tuesday for zone 354. (See LAXCFWLOX).
     High Wind Watch remains in effect from Tuesday morning
      through Wednesday afternoon for zones
      354>358-362-366>368-376-377. (See LAXNPWLOX).
     Red Flag Warning in effect from 10 AM Tuesday to 6 PM PST
      Thursday for zones 288-358-362-369>376-378>380-548. (See LAXRFWLOX).
     Fire Weather Watch in effect from Thursday evening through
      Friday afternoon for zones 288-358-362-369>376-378>380-548. (See LAXRFWLOX).
     Fire Weather Watch in effect from Tuesday morning through
      Friday afternoon for zones 354-355-377. (See LAXRFWLOX).
     Fire Weather Watch in effect from Tuesday evening through
      Wednesday afternoon for zones 366>368. (See LAXRFWLOX).
PZ...Small Craft Advisory in effect until 9 PM PST this evening
      for zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PST Tuesday for
      zone 650. (See LAXMWWLOX).
     Gale Watch in effect from Tuesday morning through Wednesday
      afternoon for zone 655. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PST Wednesday for
      zones 670-673. (See LAXMWWLOX).
     Small Craft Advisory in effect until 6 PM PST Wednesday for
      zone 676. (See LAXMWWLOX).

&&

PUBLIC...Rorke/Thompson
AVIATION...Black
MARINE...Schoenfeld/Black
SYNOPSIS...30/Smith

weather.gov/losangeles

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