Nevada, 2023

Debris Flows and Avalanche in Nevada, March 9 to 12, 2023

March 9 to 12, 2023 · NWS REV · 20 events in 9 counties and zones

Strong, even damaging west-southwest winds increased travel hazards especially to high profile trucks but also increased the danger for destructive avalanches across the region. Snow started at all elevations Thursday evening with snow levels rapidly rising Friday morning.

Where it happened

Every event with a place to put it; 6 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.

  • Tornadoes
  • Tropical storms and surge
  • Floods
  • Wind
  • Hail
  • Winter weather
  • Heat and drought
  • Cold
  • Fire, smoke and dust
  • Marine and coastal
  • Other

Open the live radar over this ground

The toll

Deaths
0
Injuries
0
Property damage
None recorded
Crop damage
None recorded
Events
20

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.

What happened

The episode as NWS REV wrote it up.

Strong, even damaging west-southwest winds increased travel hazards especially to high profile trucks but also increased the danger for destructive avalanches across the region. Snow started at all elevations Thursday evening with snow levels rapidly rising Friday morning. Heavy, wet snow (Sierra Nevada Cement) fell across higher elevation areas as snow levels rose to 7000 feet over the region. Heavy rainfall increased the possibility of flooding for lower elevation creeks, streams, along with urban drainage issues due to snow berms. Significant rises on mainstem rivers were monitored for flooding. Deep, cold snowpack absorbed most liquid precipitation during this second AR supported storm system.

What forecasters said that day

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 Reno, NV wrote its last area forecast discussion before the first event at Mar 8, 3:10 PM PST, 11 hours 50 minutes earlier.

Area forecast discussion, Mar 8, 3:10 PM PST, 11 hours 50 minutes before
Area Forecast Discussion
National Weather Service Reno NV
310 PM PST Wed Mar 8 2023

.SYNOPSIS...

After a short break in storm activity through Thursday morning, a
potent atmospheric river storm will bring rising snow levels with
strong winds, heavy mountain snow and lower elevation rain
Thursday afternoon through Friday, with possible flooding in poor
drainage areas. Additional waves of moisture will keep rain and
snow chances going at times from this weekend into next week.

&&

.DISCUSSION...

Some bands of light snow showers will linger into the evening
across parts of western Nevada along the I-80 corridor to the
north and south to Highway 50. Snow accumulations will remain
generally light with only minor impacts for roads already cleared
of snow. Breezy conditions accompanying the short wave trough
passage, along with areas of blowing dust across the Basin and
Range north of I-80 and east of Highway 95 will begin to diminish
into the evening. A quick moving short wave ridge will then bring
a brief period of clearing overnight into Thursday morning before
the next winter system moves into the region later in the
afternoon. -Amanda

A very active and impactful weather pattern for the upcoming week
will be highlighted by a surge of atmospheric river moisture
accompanied by a 150 kt subtropical jet headed directly into the
Sierra starting Thursday afternoon, then spreading across western
NV. Peak precip rates, wind speeds and impacts are expected
Thursday evening through Friday afternoon. Additional waves of
moisture, although not as intense or warm, are projected to
continue through the weekend.

Highlights for the first storm from Thursday night through the
weekend:

* WINDS: 700 mb flow of 60-70 kt, with jet stream level flow of
  120-130 kt over the Sierra, will bring strong and potentially
  damaging winds late Thursday evening through Friday evening. The
  peak gusts are likely to reach western NV during the day Friday.
  Even with some dampening of the wind speeds with precip
  occurring, wind gusts of 60-70 mph remain possible at times,
  with Sierra ridge gusts surpassing 120 mph.

* PRECIP AMOUNTS: Impressive precipitation totals are projected
  from Thursday afternoon through Saturday night, with recent
  guidance indicating 6-9" of liquid equivalent along the Sierra
  crest, 3-6" in Sierra communities, 1-2" along US-395 from
  northeast CA to the main urban areas of far western Nevada, 2-4"
  for foothill areas mainly west of US-395, and 0.25-0.5" for the
  west central NV Basin & Range. The latter portion of the
  weekend could bring another 0.50" liquid to the Tahoe area with
  around 1" near the Sierra crest, but western NV likely becomes
  more shadowed out with minimal additional rainfall through
  Sunday. These precip amounts will be capable of producing
  flooding concerns--see the hydrology segment for additional
  details.

* SNOW LEVELS/AMOUNTS: This continues to be the wild card as snow
  levels start rather low (near 4500-5500 feet) with the initial
  moisture push Thursday afternoon. The most likely scenario
  raises snow levels quickly through Thursday evening-night to
  near 8000-8500 feet. While more intense precip could
  occasionally lower snow levels by 1000-1500 feet, the majority
  of precip below 7500-8000 feet will most likely fall as rain or
  a rain-snow mix until some cooling arrives Friday afternoon-
  night. Snow levels then look to dip to 5000-6000 feet by early
  Saturday for Tahoe and western NV between I-80 and US-50, near
  7000 feet for Mono County and western NV south of US-50, but
  fall down to near 4000 feet for northeast CA-far northwest NV
  where the colder air mass makes more progress. The cold front
  then stalls and lift northward before becoming more poorly
  defined during the remainder of the weekend, with resultant snow
  levels generally around 5500-6000 feet north of I-80 and
  6000-7000 feet from I-80 southward. Snow amounts for the Sierra
  will vary quite widely by elevation but with expectations for
  several feet in the higher elevation sites, the watches for the
  eastern Sierra/Tahoe area will be upgraded to Winter Storm
  Warnings--see our latest statement for more details on potential
  snowfall amounts. For the main western NV urban areas, this
  event will be nearly all rain, with a few foothill sites above
  5000-5500 feet maybe receiving up to an inch or so of snow at
  the onset (Thursday evening) and the tail end (early AM
  Saturday) of the main storm.

For early-mid next week, the Sierra may not see much of a break as
upslope snow showers continue Sunday night-Monday. Then another
colder storm system moves through with a round of moderate-heavy
snow Monday night into Tuesday. Even beyond that, another fast
moving storm is on track for midweek. While these storms currently
appear to be colder compared to the Thursday-Saturday event and
reduce the overall flood risk, the tracks still could vary and
bring a period of higher snow levels. However, the colder storm
scenario would further compound the winter impacts for areas
already overwhelmed by excessive season-long snowfall, including
the new snow coming prior to next week. For lower elevations of
western NV, significant snowfall isn't likely, but short bursts
of snow could produce some travel impacts for the Tuesday and
Wednesday morning commutes. MJD

&&

.AVIATION...

* Some light snow showers will linger in the vicinity of Sierra
  terminals with bands of light snow showers diminishing across
  western Nevada going into the evening. A lingering light snow
  shower or two may briefly bring MVFR/IFR conditions in CIG/VIS
  for KLOL and KNFL. For the most part VFR conditions will prevail
  for western Nevada terminals overnight through Thursday morning.
  Later Thursday morning, snow shower chances will begin to
  increase across northeast California, which will spread periods
  of IFR conditions east and south towards Sierra terminals (KSVE-
  KTRK-KTVL) Thursday afternoon.

* Moderate turbulence and LLWS will subside briefly overnight but
  begin to increase once more late Thursday morning as Sierra
  ridgetop wind gusts surge to 90 kts. FL100 winds will also
  increase to 50-60 kts by 00Z Friday as well. Sierra terminals
  will see southwest wind gusts increasing to 20-30 kt Thursday
  afternoon and evening, with western Nevada terminals seeing
  wind gusts to 25 kts.

* Latest model scenarios continue to show a very active pattern
  starting Thursday night though Saturday and a followup lower
  confidence storm Monday through Wednesday next week. Aviators
  should expect periods of strong winds and turbulence, along with
  heavy precipitation to impact the region Thursday night-Saturday
  and again Monday to Wednesday next week. -Amanda

&&

.AVALANCHE WEATHER...

High confidence for a strong atmospheric river storm Thursday
night through Saturday, producing very heavy precipitation with
variable snow levels and significant impacts for avalanche
concerns.

* 24-hr Snow Water Equivalent (SWE): High-end SWE of 3-6" along
  the crest from Thursday evening through Friday afternoon, with
  hourly rates of 0.25-0.50" at times during peak intensity. SWE
  rates decrease by Friday night but additional 1-3" possible
  through the weekend.

* Snow-Liquid Ratios: Lower snow-liquid ratios of 7-10 to 1,
  except 10-13 to 1 for the Sierra crest above 9000 ft through
  Friday. Cooler air will increase snow-liquid ratios to 10-14 to
  1 for Friday night-Saturday morning.

* Winds: Strong southwest winds expected with gusts to 100-125
  mph across the ridges Thursday afternoon through Saturday
  morning.

Active pattern will continue through the middle of next week with
the highest probability for more impactful snow and wind Monday
night-Wednesday. MJD

&&

.HYDROLOGY...

Bottom Line: Increasing confidence in flooding along creeks and
streams and areas of poor drainage where deep snow may confine
flow and limit drainage. Significant rises are expected on main
stem rivers. While flooding is not currently forecast, rises to
monitor stage are now forecast for several points, and minor to
moderate flooding can't be ruled out if the system overperforms
in terms of precipitation amounts and/or prolonged periods of
higher snow levels occur.

The flood threat does not go away Sunday. Any additional rains next
week could lead to additional rises, and some rivers will be slow
to respond to the Thursday-Saturday event.

Late Thursday through Saturday, rain combined with strong winds
and high humidity will add considerable energy into our record to
near-record deep regional snowpack at mid to lower elevations.
While higher elevation and deepest snowpacks will continue to
accumulate snow and water equivalent, deep mid-elevation
snowpacks are expected to retain most of the projected rain. Some
of these areas may begin to develop preferential pathways for melt
and start releasing rainfall after prolonged periods of rain, but
are unlikely to contribute significant snowmelt to the runoff. It
is the areas of relatively shallow snowpack on the order of
inches to a couple of feet that we are most concerned about having
significant melt and contributing to the flood concerns.
Fortunately, these areas are confined to low elevation drainages
and to limited portions of the main stem rivers.

Our greatest concern continues to be creeks and streams draining
large areas of terrain with shallow snowpacks (below ~5500 feet)
and urban poor drainage areas where deep snow may be restricting
drainage. Confidence is increasing in flood impacts for these
areas.

The main-stem rivers forecasts have ramped up somewhat, but still
remain below flood stages. Keep a close eye on the Pit River into
Big Valley, the Susan River, The Middle Fork of the Feather, and
the forks and main stem of the Carson River. The Susan River will
respond very rapidly to heavy rain, while the response for the
Pit River into Big Valley and the Middle Fork of the Feather may
take several days. The latest guidance from the CNRFC now has the
East fork of the Carson and the main stem Carson River near
Carson City exceeding monitor stages.

The potential for additional rainfall early next week will require
close monitoring as the Thursday - Saturday system will help prime
the snowpack and stream responses. Check back for forecast
updates at cnrfc.noaa.gov. Changes in storm track could lead to
changes in precipitation and or rain snow elevation that could
exacerbate or mitigate flooding concerns. -Bardsley

&&

.REV Watches/Warnings/Advisories...
NV...High Wind Watch from Thursday evening through Friday evening
     NVZ001-003>005.

     Flood Watch from Thursday afternoon through Sunday morning
     NVZ001>003.

     Winter Storm Warning from 4 PM PST Thursday to 11 AM PDT Sunday
     NVZ002.

     Lake Wind Advisory until 6 PM PST this evening NVZ004.

CA...High Wind Watch from Thursday evening through Friday evening
     CAZ070.

     Flood Watch from Thursday afternoon through Sunday morning
     CAZ071>073.

     Winter Storm Warning from 4 PM PST Thursday to 11 AM PDT Sunday
     CAZ071.

     Winter Storm Warning from 4 PM PST Thursday to 11 AM PDT Sunday
     CAZ072.

     Winter Storm Warning from 4 PM PST Thursday to 11 AM PDT Sunday
     CAZ073.

&&

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

6 heavy rain, 4 flood, 4 debris flow, 3 high wind, 2 heavy snow, 1 avalanche. Local standard time, as filed.

Flood, Lyon

When
March 9, 3:00 AM PST to March 10, 3:00 AM PST
Where
Lyon County, Wellington to 4 mi WNW of Smith
Cause
Heavy Rain
Reported by
Public
Coordinates
38.750, -119.380

The public reported 4.0 mi SE of Wellington, NV, that Smith Valley fields are ponding and backing up into culverts causing additional problems near desert creek at SR-338.

Heavy Rain, Douglas

When
March 9, 6:00 AM PST to March 10, 6:00 AM PST
Where
Douglas County, 3.9 mi S of Gardnerville to Minden
Reported by
CoCoRaHS
Coordinates
38.874, -119.730

A COCORAHS (NV-DG-11 Gardnerville) located 3.9 mi S of Gardnerville, NV, and a CO-OP Observer (MINN2) located in Minden, NV, reported 24-hour rainfall totals of 1.78 and 1.52 inches respectively.

Heavy Rain, Carson City (C)

When
March 9, 6:00 AM PST to March 10, 6:00 AM PST
Where
Carson City (C) County, 3.6 mi NNW of Carson City to 3.26 mi WNW of Carson City Arpt
Reported by
CoCoRaHS
Coordinates
39.218, -119.806

A COCORAHS, NV-CC-20 Carson City, located 3.6 mi NNW of Carson City, NV, reported a 24-hour rainfall total of 1.62 inches.

Heavy Rain, Douglas

When
March 9, 7:00 AM PST to March 10, 7:00 AM PST
Where
Douglas County, 5.7 mi W of Gardnerville to 0.24 mi NNE of Mottsville
Reported by
CoCoRaHS
Coordinates
38.930, -119.836

A COCORAHS (NV-DG-23 Gardnerville) located 5.7 mi W of Gardnerville, NV, reported a 24-hour rainfall total of 2.27 inches.

Flood, Washoe

When
March 9, 7:00 AM PST to March 10, 7:00 AM PST
Where
Washoe County, 2.04 mi NNE of Steamboat to 2.03 mi NNE of Steamboat
Cause
Heavy Rain
Reported by
Public
Coordinates
39.398, -119.736

The public reported 7.0 mi NE of Washoe City, NV, that Toll Road is flooded at Geiger Grade road.

Heavy Rain, Washoe

When
March 9, 8:00 AM PST to March 10, 8:00 AM PST
Where
Washoe County, 9 mi W of Reno to 22.1 mi NNW of (Rno)cannon Arpt Ren
Reported by
CoCoRaHS
Coordinates
39.520, -119.989

A COCORAHS, NV-WH-164, located 22.1 mi NNW of Reno, NV, and COCORAHS, NV-WH-19 Verdi, located 9.0 mi W of Reno, NV, reported 24-hour rainfall totals of 1.7 inches and 1.8 inches respectively.

Heavy Rain, Lyon

When
March 9, 8:00 AM PST to March 10, 8:00 AM PST
Where
Lyon County, 2.4 mi S of Smith to 0.8 mi NE of Yerington
Reported by
COOP Observer
Coordinates
38.765, -119.320

A CO-OP observer (YRGN2) located 0.8 mi NE of Yerington, NV, and mesonet station (NSMV) located 2.4 mi S of Smith Valley, NV, reported 24-hour rainfall totals of 1.50 inches and 1.44 inches respectively.

Heavy Rain, Washoe

When
March 9, 9:00 AM PST to March 10, 9:00 AM PST
Where
Washoe County, 0.9 mi ESE of Incline Vlg to 1.04 mi E of Incline Vlg
Reported by
CoCoRaHS
Coordinates
39.225, -119.934

A COCORAHS, NV-WH-12, located 0.9 mi ESE of Incline Village, NV, reported a 24-hour rainfall total of 2.18 inches.

Avalanche, Greater Lake Tahoe Area

When
March 9, 9:15 AM PST to March 10, 9:15 AM PST
Where
Greater Lake Tahoe Area forecast zone
Reported by
Public
Coordinates
39.789, -119.640 (the zone’s center; the record gives no point)

The public reported 1.0 mi NNW of Diamond Peak Ski Resort that NV-431, the main mountain highway between Reno and Lake Tahoe basin, had been buried by an avalanche. The roadway was covered by some 20 ft. of snow according to the report.

Debris Flow, Lyon

When
March 9, 9:42 AM PST to March 10, 9:42 AM PST
Where
Lyon County, 24.16 mi SSE of Wellington to 25.47 mi SSE of Wellington
Cause
Heavy Rain / Snow Melt
Reported by
Public
Coordinates
38.447, -119.156

The public reported 7.0 mi SSE of Sweetwater Summit (Walker River Canyon) of minor debris flows and rock slides. The route was closed from Bridgeport, CA, to Mason, NV, due to flooding along NV-338 on Nevada side.

Debris Flow, Douglas

When
March 9, 9:45 AM PST to March 10, 9:45 AM PST
Where
Douglas County, 7.53 mi NNW of Topaz Lake to 9.01 mi N of Topaz Lake
Cause
Heavy Rain / Snow Melt
Reported by
Department of Highways
Coordinates
38.727, -119.558

NDOT reported 3.0 mi NNW of Holbrook Junction that US-395 was closed from Holbrook Jct. to Leviathan Mine Road due to mud and water flows on road.

Flood, Storey

When
March 9, 10:00 AM PST to March 10, 10:00 AM PST
Where
Storey County, 5.25 mi ESE of Virginia City to 5.25 mi E of Virginia City
Cause
Heavy Rain
Reported by
County Official
Coordinates
39.304, -119.554

County official reported 2.0 mi WNW Six Mile Canyon that Six Mile Canyon Road was closed from R street in Virginia City, NV, to Sam Clemens St. in Dayton, NV, due to washouts and to allow crews time for road repairs.

Flood, Washoe

When
March 9, 10:00 AM PST to March 10, 10:00 AM PST
Where
Washoe County, 2.14 mi WSW of Steamboat to 2.74 mi SW of Steamboat
Cause
Heavy Rain
Reported by
Broadcast Media
Coordinates
39.355, -119.785

The broadcast media reported that 3.0 mi NE of Washoe City, NV, of flooding in Pleasant Valley, NV.

Debris Flow, Mineral

When
March 9, 10:38 AM PST to March 10, 10:38 AM PST
Where
Mineral County, 11.99 mi WNW of Thorne to 12.14 mi NW of Hawthorne Arpt
Cause
Heavy Rain
Reported by
Department of Highways
Coordinates
38.689, -118.771

NDOT reported that 2.0 mi NW of Walker Lake, NV, US 95 was closed between Schurz, NV, and Hawthorne, NV, due to a major rockfall.

Debris Flow, Lyon

When
March 9, 5:50 PM PST to March 10, 5:50 PM PST
Where
Lyon County, 3.7 mi E of Wilson Canyon to 3.52 mi E of Wilson Canyon
Cause
Heavy Rain
Reported by
Department of Highways
Coordinates
38.821, -119.202

NDOT reported on social media 8.0 mi ENE of Smith, NV, that SR-208 in Wilson canyon was closed due a rockslide.

High Wind, Western Nevada Basin and Range

When
March 10, 3:47 AM PST
Where
Western Nevada Basin and Range forecast zone
Measured
56 kt (64 mph) measured gust
Reported by
Mesonet
Coordinates
39.927, -118.898 (the zone’s center; the record gives no point)

Mesonet station Cherry Valley (CYVNV) located 7.0 mi E of Dixie Valley, NV, reported a peak wind gust of 65 mph.

High Wind, Greater Reno/Carson City/Minden Area

When
March 10, 5:30 AM PST to 8:00 AM PST
Where
Greater Reno/Carson City/Minden Area forecast zone
Measured
71 kt (82 mph) measured gust
Reported by
Mesonet
Coordinates
39.511, -119.499 (the zone’s center; the record gives no point)

Mesonet station (SLIDE) located 0.9 mi ESE of the Mount Rose Summit (DRI), mesonet station South Verdi (NV052) located 2.0 mi SSE of Verdi, NV, and mesonet station (WASNV) located 1.3 mi SW of Washoe City, NV, reported maximum wind gusts of 82 mph, 76 mph, and 73 mph respectively.

Heavy Snow, Greater Lake Tahoe Area

When
March 10, 7:00 AM PST to March 11, 7:00 AM PST
Where
Greater Lake Tahoe Area forecast zone
Reported by
Public
Coordinates
39.789, -119.640 (the zone’s center; the record gives no point)

The public located 1.0 mi NE of the Diamond Peak Ski Base reported a 24-hour snowfall total of 10.0 inches with a 2-day snowfall total of 14 inches at 8500 feet.

High Wind, Western Nevada Basin and Range

When
March 10, 9:00 AM PST to 11:00 AM PST
Where
Western Nevada Basin and Range forecast zone
Measured
53 kt (61 mph) measured gust
Reported by
Mesonet
Coordinates
39.927, -118.898 (the zone’s center; the record gives no point)

Mesonet station Mill City (UP983) located 1.4 mi W of Mill City, mesonet station Toulon (TOUNV) located 10.1 mi of Trinity Junction, NV, and mesonet station (UP974) located 17.5 mi NE of Gerlach, NV, reported peak wind gusts 59 mph, 60 mph, and 61 mph respectfully.

Heavy Snow, Greater Lake Tahoe Area

When
March 11, 7:00 AM PST to March 12, 7:00 AM PST
Where
Greater Lake Tahoe Area forecast zone
Reported by
Public
Coordinates
39.789, -119.640 (the zone’s center; the record gives no point)

The public located at the Mount Rose Ski Base reported a 24-hour snowfall total of 12.0 inches with a 3-day storm total snowfall of 36-44 inches.

What these are

Flood
Flooding that develops more slowly than a flash flood: rivers leaving their banks, or water standing over land for an extended time.
Heavy Rain
Rainfall totals unusual for the place and season that did not produce a flood.
Avalanche
A mass of snow sliding down a mountainside that caused a death, an injury or damage.
Debris Flow
A fast-moving slurry of mud, rock and debris, usually on a slope soaked by heavy rain or stripped by a fire.
High Wind
Sustained non-thunderstorm winds of 40 mph or more for an hour, or gusts of 58 mph or more.
Heavy Snow
Snowfall reaching the local warning threshold without the other hazards of a winter storm.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

More

Every storm in Nevada in 2023Every state in 2023This day in weather historyWarnings in Nevada, March 2023

Sources

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: 1099342, 1099138, 1099144, 1099140, 1099343, 1099141, 1099145, 1099146, 1099341, 1099344, 1099345, 1099347, 1099350, 1099351, 1099352, 1099134, 1099136, 1099148, 1099133, 1099149.