Flash Flood Warning 3, NWS Los Angeles, CA

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1006 AM PST Sun Feb 4 2024

.SYNOPSIS...04/1002 AM.

A powerful atmospheric river will arrive today. This storm will
bring very heavy rain and potentially life-threatening flash
flooding, and high elevation mountain snow to much of the region
through Tuesday morning. This storm will be followed by showers
and lowering snow levels through the week.

&&

.SHORT TERM (TDY-TUE)...04/1002 AM.

***UPDATE***

A very strong storm system is arriving into the area right now and
is starting to bring one of the most dramatic weather days in
recent memory. The biggest change is a shift of the heaviest rain
and longest rain duration eastward, now centered over Los Angeles
County. Heavy rain and a high risk of dangerous flooding still
exists for Ventura and southern Santa Barbara Counties even with
this shift.

This is a DANGEROUS SYSTEM with major risks to life and property.
Many roads and freeways will flood or shutdown. Canyon roads will
experience significant rockslides. Low-lying neighborhoods will
see waters over curbs with a foot or two of water into vulnerable
homes and businesses. Many parked cars will be damaged. Mudslides
will occur over vulnerable areas. Recent burn scars will
experience deep debris flows. Several creeks and the Ventura River
will overflow their banks. Strong flows in all creeks and rivers
will pose a risk for drowning for anyone in the channels,
including the unhoused and anyone camping. Many trees will fall,
including in urban areas. Power outages could occur anywhere.
Mountain communities above 6,000 feet may be shut off for a day or
two with heavy snow covering access roads. Very large and steep
waves will make the seas extremely dangerous over the open waters
and along the coastline. Residents should heed any evacuation
orders. Stay off the roads, especially the freeways, this
afternoon through at least Monday morning.

The surface pressure gradient between KLAX and KSFO is 18.3.
This afternoon it is projected to be 20.8 mb which is only 1.2 mb
away form the all time record set in January 2008. This is one
indicator of just how very strong and dangerous this storm is.

This major storm will bring a multitude of dangerous weather
conditions to the area.

RAIN...
The deep moisture plume embedded in the warm front will interact
with very dynamic forcing this afternoon and tonight bringing a
rapid increase in the rain both in coverage and intensity. The
main rain band will move to the south tonight into Monday, and
many of the projections are now semi-stalling the band over Los
Angeles County through as late as Monday Night...which is
resulting in an increase in totals there. Behind the main band,
many showers and possible thunderstorms will bring occasionally
heavy rainfall through Tuesday morning. These showers will likely
organize into at least one band bringing a few hours of steady moderate
to heavy rain. With the flow staying southerly through the event,
favored south-facing slopes will continue to see amplified
rainfall totals, including the watersheds to several creeks and
rivers which will enhance the risk for flooding.

Impressive rain totals are still on track. The latest projections
create the need to break the totals down. Lower totals of 2 to 4
inches are expected for San Luis Obispo and northern Santa Barbara
Counties, with 4 to 8 inches in the mountains and foothills. That
is still a lot of rain which will pose flooding risks. For all
other areas, 4 to 8 inches are expected, with Los Angeles County
likely seeing the upper end of that range. Favored mountains and
foothills should fall into the 8 to 15 inch range. Rainfall rates
are expected to peak in the 0.50 to 1.00 inch per hour range, but
isolated rates up to 1.50 inches per hour are possible near
thunderstorms, the heaviest cells, and in the favored south-facing
slopes. Also, given the sheer amounts of rainfall expected in the
time period, the 3-6 hour rain rates could be problematic,
exceeding USGS thresholds which could lead to mud/debris flow
issues as well as swift water rescues in the local rivers and
streams. A FLOOD WATCH remains in effect for all areas. See
LAXFFALOX for the latest details.

WIND...
Widespread wind gusts of 50 to 70+ mph are already being reported
over San Luis Obispo and northern Santa Barbara Counties. Power
outages are starting to occur, including where our Santa Barbara
weather radio transmitters are located (currently down). These
winds will work down to the south later this afternoon and while
they will weaken some, they will remain strong through most of
tonight. Winds will peak through 6pm over San Luis Obispo and
Santa Barbara Counties, and 1pm to 1am over Ventura and Los
Angeles Counties. Expecting many trees down and many areas with
experiencing power outages. High Wind Warnings (or Winter Storm
Warnings for the combination of heavy snow and strong winds)
blanket most of the area. Winds will likely decrease significantly
late tonight into Monday.

THUNDERSTORMS...
As the cold front sweeps through, atmospheric instability will
increase across the area. This instability will combine with
diffluence aloft and a low level jet to bring a threat of
thunderstorms to most areas in the today and Monday with the
threat lingering over Los Angeles county through the day on
Tuesday. Given the forecasted shear profile in the atmosphere,
there will be a threat of waterspouts over the coastal waters and
even small tornadoes over the land. Also, there is the potential
for some strong downburst (straight-line) winds with any convective
activity. As for rain rates, any thunderstorm activity could
generate very high rates, on the order of around 1.50 inches per
hour.

SNOWFALL...
Snow levels are still fairly low (it is snowing at Sandberg), but will
start to slowly rise today in the warm southerly flow and will
increase to 6500-7500 ft today. After the cold front passes the
snow levels will drop to 5000-6000 ft Monday/Monday night. They
will fall further to 4000-5000 ft on Tuesday. Since snowfall
totals of 2-4 feet are likely above 7000 feet with 10-20 inches
between 6000 and 7000 feet and 3-10 inches between 5000 and 6000
feet. With strong southerly winds, potentially gusting up to 80
MPH, significant winter storm conditions are likely and WINTER
STORM WARNINGS are in effect for the eastern San Gabriel Mountains
and the northern Ventura county mountains. Future shifts may need
to issue Winter Weather Advisories for other mountain areas,
depending on how things develop. See LAXWSWLOX for the latest
details.

Temperatures...
High temps each day will be within 2 degrees either side of 60
each day.

.LONG TERM (WED-SAT)...03/121 PM.

For the extended, models are in the best agreement, but the
differences will not impact the forecast too much. Essentially,
for Wednesday through Saturday, the area will remain under a
northwesterly flow aloft. For Wednesday, skies will likely be
partly cloudy and a stray light shower can not be ruled out just
about anywhere. For Thursday/Friday, a weak system is forecast to
move across the area, bringing the possibility of light to
moderate precipitation to the area. On Saturday, conditions look
to improve in the wake of the Thursday/Friday system.

&&

.AVIATION...04/1658Z.

At 1645Z, there was no marine inversion or marine layer at KLAX.

Overall, low confidence in 18Z TAF package. High confidence in
development of moderate to heavy rain with associated CIG/VSBY
restrictions. Heaviest rain will occur across San Luis Obispo and
Santa Barbara counties through early this evening and across
Ventura/LA counties late this evening through the overnight hours.
However, low confidence in timing of flight category changes with
CIGs/VSBYs running the gamut from MVFR to LIFR.

Also, strong southeasterly winds will impact all sites through the
period.

KLAX...Low confidence in 18Z TAF. High confidence in development
of heavy rain this evening and overnight with CIG/VSBY
restrictions. However, low confidence in exact flight categories
and timing of category changes. Moderate confidence in east-
southeast winds, gusting 20-25 kt, 22Z-07Z.

KBUR...Low confidence in 18Z TAF. High confidence in development
of heavy rain this evening and overnight with CIG/VSBY
restrictions. However, low confidence in exact flight categories
and timing of category changes.

&&

.MARINE...04/858 AM.

Very dangerous marine conditions are expected across all the
coastal waters today through tonight. Strong southerly winds will
develop today with STORM FORCE winds (gusts 50-60 kt) likely
across all the Outer Waters, the Inner Waters north of Point Sal
and the Santa Barbara Channel. Strong GALE force winds (gusts
35-45 kt) will impact the Inner Waters south of Point Mugu. Along
with the winds, very large seas will impact the waters with 20-28
foot seas from Point Conception northward and 10-20 foot seas
elsewhere. South-facing harbors, such as Port San Luis and Santa
Barbara Harbor, will be impacted with large, breaking waves.

Late tonight, winds and seas will begin to subside. High
confidence in some combination of Small Craft Advisory (SCA) level
winds and seas will continue through Monday night.

For Tuesday and Wednesday, there is a 60-80% chance of SCA level
winds and seas across the Outer Waters and the Inner Waters north
of Point Sal. Elsewhere, there is a 30-40% chance of SCA level
winds.

For Thursday, high confidence in winds and seas remaining below
SCA levels.

Along with the winds and high seas, there will be a 20 percent
chance of thunderstorms today through Monday. Any thunderstorms
that develop will be capable of brief heavy rain, gusty and
erratic winds, steep and rough seas, dangerous cloud to surface
lightning, and possible waterspouts.

&&

.BEACHES...04/858 AM.

An extended period of high surf will affect southwest California
beaches through Monday. A southerly wind driven swell will
develop today, bringing significant surf to south and southwest
facing beaches. North of Point Conception, surf heights of 14-18
feet with local sets to 20 feet are expected with 8 to 12 foot
surf south of Point Conception.

This large wind swell will create breaking waves and a possible
push of water into unprotected SOUTH to SOUTHWEST facing areas
like Port San Luis and Santa Barbara Harbor & Pier, and El Capitan
State Beach.

A combination of strong winds creating large wind driven waves
and higher water levels due to lower atmospheric pressure will
result in a threat of coastal flooding. For south to west facing
beaches along the the Central Coast, moderate coastal flooding
coastal flooding impacts are expected CONTINUOUSLY through the
Monday early morning high tide, due to the luckily miss aligned
high tides and peak surf. For beaches south of Point Conception,
moderate coastal flooding is possible for SOUTH facing harbors
such as Santa Barbara Harbor, mainly during high tide early Monday
morning.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Flood Watch remains in effect through Tuesday afternoon for
      zones 38-87-88-340>358-362-366>383-548. (See LAXFFALOX).
     High Wind Warning in effect until 10 PM PST this evening for
      zones 38-340>344-346>352-549-550. (See LAXNPWLOX).
     High Surf Advisory in effect until 9 PM PST Monday for zones
      87-340-346-349-350-354-362-366. (See LAXCFWLOX).
     Wind Advisory in effect until 6 AM PST Monday for zones
      87-366>368-371>373-548. (See LAXNPWLOX).
     Coastal Flood Advisory in effect from 1 AM to 9 AM PST Monday
      for zones 87-349-350-354-362-366. (See LAXCFWLOX).
     High Wind Warning in effect until 6 AM PST Monday for zones
      88-369-370-375-376-378-379-381>383. (See LAXNPWLOX).
     Coastal Flood Advisory in effect until 9 AM PST Monday for
      zones 340-346. (See LAXCFWLOX).
     High Wind Warning in effect until 4 AM PST Monday for zones
      345-353. (See LAXNPWLOX).
     Wind Advisory in effect until 3 PM PST this afternoon for
      zones 354>358-362-374. (See LAXNPWLOX).
     High Wind Warning in effect from 3 PM this afternoon to 10 PM
      PST this evening for zones 354>358-362-374. (See LAXNPWLOX).
     Winter Storm Warning in effect until 6 PM PST Tuesday for
      zones 377-380. (See LAXWSWLOX).
PZ...Gale Warning in effect until 3 AM PST Monday for zone 655. (See LAXMWWLOX).

&&

PUBLIC...RAT/DB/Rorke/Kittell
AVIATION...RAT
MARINE...RAT
BEACHES...RAT
SYNOPSIS...MW/Schoenfeld/DB

weather.gov/losangeles

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

Preliminary Local Storm Report
National Weather Service Los Angeles/Oxnard CA
1240 PM PST Sun Feb 4 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0920 AM     Non-Tstm Wnd Gst 2 NNE Los Olivos        34.70N 120.10W
02/04/2024  M58 MPH          Santa Barbara      CA   Mesonet

            Mesonet station TT480 Sbcfd Portable 1.

1210 PM     Non-Tstm Wnd Gst 1 SE Santa Ynez         34.60N 120.09W
02/04/2024  M58 MPH          Santa Barbara      CA   Mesonet

            Mesonet station AP901 Santa Ynez.

0700 AM     Non-Tstm Wnd Gst Refugio State Beach     34.46N 120.08W
02/04/2024  M59 MPH          Santa Barbara      CA   Mesonet

            Mesonet station 623SE Sce Refugio Beach.

1000 AM     Non-Tstm Wnd Gst 3 ENE Cayucos           35.46N 120.86W
02/04/2024  M59 MPH          San Luis Obispo    CA   Mesonet

            Mesonet station PG569 Whale Rock Rsvr (PGE).

1010 AM     Non-Tstm Wnd Gst 3 SW Guadalupe          34.93N 120.61W
02/04/2024  M59 MPH          Santa Barbara      CA   Mesonet

            Mesonet station 417PG Guadalupe.

1220 PM     Non-Tstm Wnd Gst 6 ENE Santa Margarita   35.41N 120.53W
02/04/2024  M59 MPH          San Luis Obispo    CA   Mesonet

            Mesonet station PG190 Flying Lady Rd (PGE).

0900 AM     Non-Tstm Wnd Gst 5 W Lompoc              34.67N 120.55W
02/04/2024  M60 MPH          Santa Barbara      CA   Mesonet

            Mesonet station 449PG Renwick Ave.

0928 AM     Non-Tstm Wnd Gst 2 N Orcutt              34.90N 120.45W
02/04/2024  M60 MPH          Santa Barbara      CA   ASOS

            ASOS station KSMX Santa Maria Apt.

1120 AM     Non-Tstm Wnd Gst 1 E Big Pines           34.38N 117.66W
02/04/2024  M60 MPH          Los Angeles        CA   Mesonet

            Mesonet station SE547 Ford Observatory
            (SCE).

1210 PM     Non-Tstm Wnd Gst 5 NNE Goleta            34.50N 119.79W
02/04/2024  M60 MPH          Santa Barbara      CA   Mesonet

            Mesonet station 422SE Painted Cave Rd (SCE).

0902 AM     Non-Tstm Wnd Gst 3 SSE San Luis Obispo   35.23N 120.63W
02/04/2024  M61 MPH          San Luis Obispo    CA   ASOS

            ASOS station KSBP San Luis Obispo Apt.

0935 AM     Non-Tstm Wnd Gst 1 WSW Figueroa Mountain 34.73N 120.01W
02/04/2024  M61 MPH          Santa Barbara      CA   Mesonet

            Mesonet station FGMC1 Figueroa Mountain
            RAWS.

1020 AM     Non-Tstm Wnd Gst Gaviota                 34.47N 120.21W
02/04/2024  M61 MPH          Santa Barbara      CA   Mesonet

            Mesonet station SE239 Gaviota (SCE).

0819 AM     Non-Tstm Wnd Gst 4 SSW Lompoc            34.60N 120.49W
02/04/2024  M62 MPH          Santa Barbara      CA   Mesonet

            Mesonet station EW2332 Lompoc.

0950 AM     Non-Tstm Wnd Gst 2 WSW Santa Margarita   35.36N 120.66W
02/04/2024  M62 MPH          San Luis Obispo    CA   Mesonet

            Mesonet station PG119 TV Towers (PGE).

1046 AM     Non-Tstm Wnd Gst 5 WSW Figueroa Mountain 34.73N 120.07W
02/04/2024  M62 MPH          Santa Barbara      CA   Mesonet

            Mesonet station TT594 Sbcfd Portable 2.

1150 AM     Non-Tstm Wnd Gst 3 WNW Refugio State Bea 34.48N 120.12W
02/04/2024  M62 MPH          Santa Barbara      CA   Mesonet

            Mesonet station 367SE Sce Coastal View.

1134 AM     Non-Tstm Wnd Gst 5 W Lompoc              34.67N 120.56W
02/04/2024  M63 MPH          Santa Barbara      CA   Mesonet

            Mesonet station TT414 Vandenberg Portable.

0930 AM     Non-Tstm Wnd Gst 10 WNW Gaviota          34.52N 120.38W
02/04/2024  M64 MPH          Santa Barbara      CA   Mesonet

            Mesonet station SE687 Dangemond (SCE).

1000 AM     Non-Tstm Wnd Gst 5 E Cambria             35.53N 121.00W
02/04/2024  M64 MPH          San Luis Obispo    CA   Mesonet

            Mesonet station PG594 Green Valley Rd (PGE).

0900 AM     Non-Tstm Wnd Gst 8 SSW Lake Nacimiento   35.62N 120.92W
02/04/2024  M65 MPH          San Luis Obispo    CA   Mesonet

            Mesonet station PG494 Adelaida Foothills
            (PGE).

1040 AM     Non-Tstm Wnd Gst 2 E Cayucos             35.45N 120.87W
02/04/2024  M66 MPH          San Luis Obispo    CA   Mesonet

            Mesonet station PG741 Cayucos Road.

1150 AM     Non-Tstm Wnd Gst 8 W Gaviota             34.47N 120.36W
02/04/2024  M66 MPH          Santa Barbara      CA   Mesonet

            Mesonet station SE456 San Agustin (SCE).

0809 AM     Non-Tstm Wnd Gst 2 NW Gaviota            34.49N 120.24W
02/04/2024  M68 MPH          Santa Barbara      CA   Mesonet

            Mesonet station GVTC1 Gaviota Hills RAWS.

1000 AM     Non-Tstm Wnd Gst 2 NE Vandenberg Village 34.73N 120.44W
02/04/2024  M68 MPH          Santa Barbara      CA   Mesonet

            Mesonet station PG825 Divide-Cabrillo.

1020 AM     Non-Tstm Wnd Gst 1 N Morro Bay           35.38N 120.85W
02/04/2024  M68 MPH          San Luis Obispo    CA   Mesonet

            Mesonet station 072PG Hillcrest Drive.

1010 AM     Non-Tstm Wnd Gst 7 E Black Mountain      35.38N 120.22W
02/04/2024  M69 MPH          San Luis Obispo    CA   Mesonet

            Mesonet station PG775 Lewis Ranch Road.

1020 AM     Non-Tstm Wnd Gst 4 WNW Atascadero        35.50N 120.76W
02/04/2024  M69 MPH          San Luis Obispo    CA   Mesonet

            Mesonet station PG191 El Monte Rd (PGE).

1135 AM     Non-Tstm Wnd Gst 10 SSW California Valle 35.19N 120.08W
02/04/2024  M70 MPH          San Luis Obispo    CA   Mesonet

            Mesonet station BRHC1 Branch Mtn RAWS.

1040 AM     Non-Tstm Wnd Gst 12 NNE Los Alamos       34.92N 120.22W
02/04/2024  M71 MPH          Santa Barbara      CA   Mesonet

            Mesonet station PG611 Tepesquet Canyon Road.

1200 PM     Non-Tstm Wnd Gst 8 S Agua Dulce          34.39N 118.34W
02/04/2024  M71 MPH          Los Angeles        CA   Mesonet

            Mesonet station SE678 Magic Mtn Truck Trl
            (SCE).

1100 AM     Non-Tstm Wnd Gst 3 NNE Los Alamos        34.79N 120.26W
02/04/2024  M72 MPH          Santa Barbara      CA   Mesonet

            Mesonet station PG665 Cat Canyon Road.

1140 AM     Non-Tstm Wnd Gst 5 ENE Cayucos           35.49N 120.82W
02/04/2024  M72 MPH          San Luis Obispo    CA   Mesonet

            Mesonet station PG633 Old Creek Road.

0950 AM     Non-Tstm Wnd Gst 7 N Cayucos             35.55N 120.91W
02/04/2024  M73 MPH          San Luis Obispo    CA   Mesonet

            Mesonet station PG175 Camino Del Capitan
            (PGE).

0854 AM     Non-Tstm Wnd Gst 12 SE Point Arguello    34.45N 120.47W
02/04/2024  M74 MPH          Santa Barbara      CA   Mesonet

            Mesonet station XCPT Pt. Conception
            Lighthouse.

1210 PM     Non-Tstm Wnd Gst 2 ENE San Luis Obispo   35.28N 120.63W
02/04/2024  M75 MPH          San Luis Obispo    CA   Mesonet

            Mesonet station PG807 High School Hill.

1000 AM     Non-Tstm Wnd Gst 4 NE San Luis Obispo    35.31N 120.60W
02/04/2024  M77 MPH          San Luis Obispo    CA   Mesonet

            Mesonet station PG715 Mt. Lowe (PGE).

1044 AM     Non-Tstm Wnd Gst 4 E Vandenberg Village  34.71N 120.39W
02/04/2024  M77 MPH          Santa Barbara      CA   Mesonet

            Mesonet station PUSC1 Purisima Hills.

0920 AM     Non-Tstm Wnd Gst 7 SSW Lompoc            34.57N 120.50W
02/04/2024  M78 MPH          Santa Barbara      CA   Mesonet

            Mesonet station PG852 De La Concepcion.

1100 AM     Non-Tstm Wnd Gst 5 W Santa Margarita     35.39N 120.71W
02/04/2024  M79 MPH          San Luis Obispo    CA   Mesonet

            Mesonet station PG223 TV Towers Rd 2 (PGE).

0920 AM     Non-Tstm Wnd Gst 3 SSW Atascadero        35.45N 120.71W
02/04/2024  M80 MPH          San Luis Obispo    CA   Mesonet

            Mesonet station PG210 Falcon Rd (PGE).

&&

Preliminary Local Storm Report
National Weather Service Los Angeles/Oxnard CA
1247 PM PST Sun Feb 4 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1243 PM     Non-Tstm Wnd Dmg San Luis Obispo         35.27N 120.66W
02/04/2024                   San Luis Obispo    CA   Emergency Mngr

            Over 22,000 people were reported without
            power in San Luis Obispo county due to the
            strong winds.

1245 PM     Non-Tstm Wnd Dmg Santa Barbara           34.43N 119.72W
02/04/2024                   Santa Barbara      CA   Emergency Mngr

            Over 10,000 people were reported to have
            lost power in Santa Barbara county due to
            the strong winds.

&&

Preliminary Local Storm Report
National Weather Service Los Angeles/Oxnard CA
206 PM PST Sun Feb 4 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0130 PM     Non-Tstm Wnd Dmg 2 E Santa Barbara       34.43N 119.69W
02/04/2024                   Santa Barbara      CA   Public

            Strong winds knocked down a tree, resulting
            in some downed power lines.

&&