A powerful winter storm impacted Central and Southern California with heavy rain and snow, gusty winds and widespread urban flooding. The heaviest rainfall totals (4-10 inches) fell across San Luis Obispo and Santa Barbara counties due to the influence of an atmospheric river.
Every event with a place to put it; 1 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS LOX wrote it up.
A powerful winter storm impacted Central and Southern California with heavy rain and snow, gusty winds and widespread urban flooding. The heaviest rainfall totals (4-10 inches) fell across San Luis Obispo and Santa Barbara counties due to the influence of an atmospheric river. With such rainfall totals, numerous reports of flooding were received in these areas. Across Ventura and Los Angeles counties, rainfall totals were less, but still significant. Ventura county received 2 to 6 inches of rainfall with 1-4 inches across Los Angeles county. With snow levels around 5000 feet, significant snowfall fell in the mountains of Ventura and Los Angeles counties with 1 to 2 feet of snowfall reported. Along with the precipitation, southerly winds, gusting up to 80 MPH, impacted the area.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Los Angeles, CA wrote its last area forecast discussion before the first event at Jan 27, 5:56 AM PST, 4 minutes earlier.
Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
556 AM PST Wed Jan 27 2021
.SYNOPSIS...27/320 AM.
A well defined and strong storm system will bring heavy rain
across San Luis Obispo and Santa Barbara Counties through
Thursday with lighter amounts to the south. The front sags
southward into Ventura and Los Angeles Counties by Thursday
afternoon into Friday. Heaviest rainfall across the southern
counties will occur Thursday night into Friday morning. Several
inches of rain are expected with flooding concerns including recent
burn areas. Several feet of high elevation mountain snow is also
expected, along with moderate to strong south winds. Much quieter
weather expected over the weekend into early Monday.
&&
.SHORT TERM (TDY-FRI)...27/312 AM.
An impressive and well defined storm system will bring copious
amounts of precipitation across San Luis Obispo and Santa Barbara
Counties this morning through Thursday before the frontal boundary
starts to sag southward affecting Ventura and Los Angeles Counties
with the heavier rain Thursday afternoon or evening through Friday
morning. Showers will start to taper off through Friday afternoon
and evening.
Latest GOES-17 WV Imagery (lower level) indicated a well defined
Atmospheric River developing across the NW portion of San Luis
Obispo County this morning. Rain will become heavy today as a
moist deep layer plume within southwest flow and with good divergence
aloft enhancing lift will move across San Luis Obispo County and
the Santa Barbara Central Coast this morning. Rainfall started across
the NW portion of SLO County last evening where a half inch of rain
has already fallen. The main focus of the Atmospheric River will
continue across SLO and SBA Counties as the front stalls through
at least Thursday before it starts to sag south across Ventura and
L.A. Counties Thursday late afternoon/Evening through the early
Friday morning when the heaviest rain is expected to occur.
Latest deterministic model runs keep things pretty consistent
from earlier runs. Have tweaked POPs down a tad for eastern L.A.
County this morning as some warm frontal moisture will develop
across Ventura County and western L.A. County by mid morning with
lighter rainfall expected. Rain is expected to become more
widespread across L.A. County by this afternoon, but remain
relatively light. This will be a slow moving system through
Thursday afternoon. In fact, as the upper trough becomes more
elongated N to S off the coast, the storm will pivot to a more S
to N direction which should bring a temporary stop to rain across
L.A. County, or at least most of the County this evening through
mid- morning Thursday. However, by Thursday, the cold front will
start to move south into Southern Santa Barbara and Ventura
Counties and then across L.A. County by Thursday late afternoon or
evening and bring a good 6 hours of heavy rain and snow over the
area before tapering off late Friday morning into the afternoon.
With such a long period of steady heavy rain across San Luis Obispo
expected through Thursday, 3-6 inches of rain, with locally 8-10
inches expected across foothills, especially around the Santa Lucia
Range. A Flash Flood Watch is in effect early this morning through
Thursday evening for the San Luis Obispo coast and foothills including
the Avila Burn Scar. Rainfall rates near 2 inches in 3 hours could
result in dangerous flash flooding to roads and creeks as well as
debris flows.
Heavy rainfall is also expected across the Santa Barbara South Coast
and adjacent foothills 2-5 inches for coast and foothills 5-8
inches in the Santa Ynez Range. The heaviest rain is not expected
to reach these areas until Thursday morning. There is a good
chance that a Flash Flood Watch will be needed for the Cave Burn
Scar in Santa Barbara County Thursday morning, but will let the
day shift look at this closer.
For Los Angeles and Ventura Counties, 1.5 to 3.5 inches are expected,
and 2 to 5 inches in the foothills and mountains...with the upper end
of that range in Ventura County as they will be in the plume longer.
With these types of amounts, expect peak rain rates between 0.25
and 0.75 inches per hour. When the system moves through the area Thursday
into Friday, more Flash Flood Watches may be needed, especially for
the recent burn areas in L.A. County. As the front sags south on Thursday,
cold air will filter in from the north and cause the atmosphere
to become more unstable. Slight chance for thunderstorms are in
the forecast for the tail end of the storm Thursday night into
Friday. Snow levels will generally be 5000 to 6000 foot range,
except closer to 4500 Thursday night into Friday behind the front.
Mountains above 6000 feet should expect several feet of snow,
depending on how long they are in the moisture plume. Winter Storm
Warnings are in effect for Santa Barbara and Ventura Counties and
the Winter Storm Watch will be likely be upgraded later today for
the L.A. County Mountains as the bulk of the snow will occur
Thursday afternoon through Friday morning. Expect strong southerly
winds across the mountains ahead and with the front. The strong
winds are highlighted in the winter products. For the other
locations, Expect gusty southerly winds for most other areas
sometime this week, strongest and most persistent across Santa
Barbara and San Luis Obispo Counties...as well as the Ventura
Mountains. This includes the San Luis Obispo County Coasts and
hills, where a High Wind Warning is in effect. High temperatures
will continue to remain around 10 degrees below normal for this
time of year.
.LONG TERM (SAT-TUE)...27/441 AM.
Friday's storm system will move out quickly Friday night with mostly
sunny skies through the weekend. There will be some lingering clouds
hanging around the foothills on Saturday. High temperatures will trend
up 3-6 degrees on Saturday with an additional 3-6 degrees of warming
Sunday. High temperatures will be near normal by Sunday. Latest
models are in pretty good agreement through Tuesday as a weak system
brushes across San Luis Obispo and Santa barbara Counties and northern
slopes Monday through Tuesday. Impacts look minimal with only
light rain expected.
&&
.AVIATION...27/1350Z.
At 12Z at KLAX, there was no marine layer nor an inversion, but
there was a moist layer up to 12000 feet.
Across SLO County and most of SBA Counties, expect widespread
MVFR cigs, except LIFR to VLIFR cigs in the foothills and mtns
through the period. There will be light to moderate rain much of
the time, (except snow in the highest mountain elevations.
Across Ventura and Los Angeles Counties, expect skies to be mostly
cloudy through the period. There will be a chance of light rain,
especially in the foothills and mountains, with snow at higher
elevations. Conditions will be mostly low VFR or high MVFR,
except LIFR to VLIFR in the foothills and mountains.
Gusty SE to S winds are expected from Ventura County northward and
in the mountains. Winds will be strongest across SLO County and in
the mtns of SBA County.
KLAX...Moderate confidence in the 12Z TAF. Expect mostly cloudy
skies though the period, with conditions mostly VFR. However,
there is a 20-30% of MVFR cigs at times. There is a 20% chance of
light rain, mainly this afternoon into tonight. There is a 20-30%
chance of an east wind component as high as 12 kt through 18Z
this morning. There is a 20% chance that east or southeast winds
will persist all day. There is a good chance of an extended
period of east winds tonight through Thursday night.
KBUR...Moderate confidence in the 12Z TAF. Expect mostly cloudy
skies though the period, with conditions fluctuating between low
VFR and high MVFR. There is a 30% chance of light rain, mainly
this afternoon into tonight. There is a 30% chance of SE wind
gusts over 25 kt this afternoon into tonight.
&&
.MARINE...27/522 AM.
Moderate to high confidence in the forecast. Conditions across
the coastal waters will continue to deteriorate today, especially
for the northern waters.
Across the inner coastal waters north of Pt. Sal and across the
northern outer waters zone (PZZ670), STORM FORCE SE to S winds
of 30 to 40 kt with gusts to 50 kt are expected thru early Thu.
There could be isolated gusts to 55 kt. There will also be large
hazardous seas as high as 14 to 18 ft. Winds are expected to
diminish to Small Craft Advisory (SCA) levels by mid morning Thu,
then below SCA level Thu night. However, seas will remain at or
above SCA levels thru at least Fri, and possibly Fri night.
Across the central outer waters zone (PZZ673), Gale force SE to S
winds are expected thru early Thu. Local STORM FORCE wind gusts
to 50 kt are possible this afternoon into tonight. Seas will also
become very large, at 14 to 17 ft. Winds are expected to diminish
to SCA levels by mid or late morning Thu, then below SCA levels
Thu night. However, seas will remain at or above SCA levels thru
Fri night.
Across the southern outer waters zone (PZZ676) SCA level SE to S
winds will increase to Gale force by mid morning, then persist
through Thu afternoon. Winds will drop to SCA levels by late Thu
afternoon, and below SCA level late Thu night, but seas will
likely remain at or above SCA levels thru Fri.
Across the Santa Barbara Channel, SCA level SE winds will
increase to Gale force this afternoon. Gale force winds will
continue through early Thu evening, then winds will shift to
SW and diminish, falling below SCA levels by midnight. Winds will
be strongest across western portions. Steep short period seas are
expected later today thru Thu evening.
Across the souther inner waters. SCA levels SE-S winds will
develop this morning, then continue through late Thu night before
winds shift to SW and diminish below SCA levels. Winds will be
strongest across western sections today thru Thu morning, then
will become widespread Thu afternoon and evening. Steep short
period seas are expected, especially late tonight thru Thu night.
&&
.BEACHES...27/531 AM.
High surf will continue as another storm system will bring large
swells to the coastal waters thru Thu night, and high surf to the
Central Coast into Fri. Very strong southerly winds will continue
across the Central Coast and in the coastal waters through early
Thursday. Surf is expected to peak at 10 to 16 feet later today
into early Thursday.
Moderate coastal flooding is possible this morning and again Thu
morning within a few hours of the high tide along the Central
Coast. The main area of concern will be Port San Luis. There will
be strong and dangerous rip currents on Central Coast beaches
with beach erosion likely.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Wind Warning in effect until 10 AM PST Thursday for
zones 34-51. (See LAXNPWLOX).
Storm Warning in effect until 9 AM PST Thursday for zone 34. (See LAXMWWLOX).
Coastal Flood Advisory in effect until noon PST Thursday for
zone 34. (See LAXCFWLOX).
High Surf Advisory in effect until 6 PM PST Friday for zones
34-35. (See LAXCFWLOX).
Flash Flood Watch in effect through Thursday evening for zone
34. (See LAXFFALOX).
Wind Advisory in effect until 4 PM PST Thursday for zones
35>39. (See LAXNPWLOX).
Winter Storm Warning in effect until 3 AM PST Friday for zone
52. (See LAXWSWLOX).
Winter Storm Warning in effect from 9 AM this morning to noon
PST Friday for zone 53. (See LAXWSWLOX).
Wind Advisory in effect until 3 PM PST Thursday for zone 54. (See LAXNPWLOX).
Winter Storm Watch in effect from Thursday afternoon through
Friday afternoon for zone 54. (See LAXWSWLOX).
PZ...Small Craft Advisory in effect until 3 PM PST this afternoon
for zone 650. (See LAXMWWLOX).
Gale Warning in effect from 3 PM this afternoon to 9 PM PST
Thursday for zone 650. (See LAXMWWLOX).
Small Craft Advisory in effect from 9 AM this morning to 3 AM
PST Friday for zone 655. (See LAXMWWLOX).
Gale Warning in effect until 9 AM PST Thursday for zone 673. (See LAXMWWLOX).
Small Craft Advisory in effect until 9 AM PST this morning
for zone 676. (See LAXMWWLOX).
Gale Warning in effect from 9 AM this morning to 3 PM PST
Thursday for zone 676. (See LAXMWWLOX).
&&
.HAZARD POTENTIAL OUTLOOK (FRI-TUE).
Moderate to heavy rainfall and mountain snow will turn to showers
Friday. There is a slight chance of thunderstorms Friday.
Rainfall intensities could result in debris flow issues for the
recent burn areas. Large surf will likely linger into Friday on
the Central Coast.
&&
PUBLIC...Kaplan
AVIATION...DB
MARINE...DB
BEACHES...DB
SYNOPSIS...Kaplan
weather.gov/losangelesThe Vandenberg AFB radar (KVBX), 47 km away, was scanning. The volume nearest the first event began at 08:59 UTC.
4 high wind, 3 winter storm, 3 flash flood. Local standard time, as filed.
Winter storm conditions impacted the mountains of Santa Barbara county. Snowfall totals of 4 to 8 inches (above 5000 feet) and southerly winds, gusting to 70 MPH, produced hazardous winter weather conditions.
Winter storm conditions impacted the mountains of Ventura county. Snowfall totals around 12 inches were reported at 5000 feet. The snow combined with southerly winds, gusting to 70 MPH, to generate hazardous winter weather conditions.
Winter storm conditions impacted the mountains of Los Angeles county. Snowfall totals of 1 to 2 feet above 5000 feet were reported. The snow combined with southerly winds, gusting to 70 MPH, to generate hazardous winter weather conditions.
Strong and gusty southerly winds impacted the coastal areas of San Luis Obispo county. Some peak wind reports from the local Mesonet include: TV Towers (gust 73 MPH) and High School Hill (gust 62 MPH).
Strong and gusty southerly winds impacted the mountains of San Luis Obispo county. Some peak wind reports from the local Mesonet include: Friis (gust 70 MPH) and Mount Lowe (gust 62 MPH).
Strong and gusty southerly winds impacted the interior valleys of San Luis Obispo county. Some peak wind reports from the local Mesonet include: Lewis Ranch Road (gust 79 MPH), Navajo Flats (gust 70 MPH) and Cholame (gust 66 MPH).
Strong and gusty southerly winds impacted the Cuyama Valley in Santa Barbara county. The sensor at Cuyama reported a peak wind gust of 62 MPH.
Heavy rain produced flash flooding in the community of Cambria in San Luis Obispo county. Along Sherwood Drive, several homes were inundated with water and mud, due to the heavy rain.
Heavy rain produced significant urban flooding in the community of Cambria. Along Windsor Boulevard, a vehicle was stuck with flooding impacted the roadway. The motorist was rescued.
Heavy rain fell over the Avila Fire burn scar, producing a mud and debris flow. The northbound lanes of Highway 101 were closed due to mud and debris from the burn scar.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2021Every state in 2021This day in weather historyWarnings in California, January 2021
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 942745, 942746, 942747, 942741, 942744, 942742, 942743, 942748, 942750, 942749.