A series of eastern Pacific winter storm pulses, occasionally aided by induction of warmer sub-tropical moisture, caused a variety of hazardous winter conditions that disrupted holiday travel and commerce over the Sierra and western NV.
Every event with a place to put it; 13 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 REV wrote it up.
A series of eastern Pacific winter storm pulses, occasionally aided by induction of warmer sub-tropical moisture, caused a variety of hazardous winter conditions that disrupted holiday travel and commerce over the Sierra and western NV.
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 Dec 21, 3:08 AM PST, 4 hours 52 minutes earlier.
Area Forecast Discussion
National Weather Service Reno NV
308 AM PST Tue Dec 21 2021
...MAJOR TRAVEL DISRUPTIONS MID WEEK THROUGH THE HOLIDAY WEEKEND...
.SYNOPSIS...
Stormy weather returns late Tuesday and Wednesday with rain and
snow, mainly for the Sierra and northeast California. Be prepared
for major travel disruptions and delays in the Sierra by
Wednesday. Snow potential increases in western Nevada by late
week with travel headaches due to snow possible this holiday
weekend.
&&
.SHORT TERM...
** Main Message for Sierra Travel Through the Holiday Weekend**
Once the snow starts this evening, travel across the Sierra will
become progressively more difficult to nearly impossible at times
through this weekend. Be prepared for long delays and quickly
changing conditions over area passes.
Low stratus will likely continue to linger over the Honey Lake area
through the morning. There are indications this morning that
freezing fog will once again redevelop over some previously affected
areas. Chances do remain low, however, due to dampened radiation
cooling under an umbrella of mid and high level cloudiness. Locations
affected could see freezing fog quickly thicken over their area
with the potential for significantly reduced visibilities and
slick surfaces.
Turning to the broader weather picture, the next appetizer storm is
forecast to move into the region this evening. Timing of Winter
Weather Advisory for 7 PM tonight still looks consistent with
latest high resolution models.
Hi-Res ensemble guidance (HREF) brings in snow across the the higher
elevation areas of the Sierra in western Lassen and Plumas county
early this evening (00-03Z Wed). Snow will spread overnight into
Wednesday morning east into the rest of northeast CA, and south
along the Sierra Crest into eastern El Dorado/Alpine counties on
the western fringe of the Lake Tahoe Basin.
Snow levels are expected to fluctuate in those areas south of
Lassen/Plumas as this first wave of precipitation moves into the
region. Extra complications arise as snow amounts could vary
widely in some Sierra valleys where localized colder air enhances
snowfall in those areas. Generally speaking expect snow levels
between 5000-6000' with travel impacts expected to begin in the
Sierra later tonight into Wednesday morning. For details on snow
amounts check the Winter Weather Advisories.
Moderate snow showers will continue in the Sierra on Wednesday with
increasingly strong storms forecast through the Christmas weekend.
- Amanda
.LONG TERM...Thursday through the holiday weekend...
Short Attention Span Highlights:
* Unsettled conditions will impact much of the West through the
holiday weekend. Check your flight status routinely and keep an
eye on road conditions by checking with CALTRANS and NDOT.
* Periods of most concern: Late Wed-Thurs and Sat-Sun. Intense and
heavy snow may produce the most impactful and hazardous travel
conditions.
* SIERRA and NORTHEAST CA PASSES -- Major travel impacts with very
long travel times and possibly periodic road closures,
especially starting Wednesday night. While snowfall rates may
lessen late Thursday night and Friday, snow-covered roads will
likely continue to create travel issues. Heavier snow returns
over the weekend.
* WRN NV VALLEYS and FOOTHILLS- rain or a rain/snow mix through
Thursday afternoon with little to no impact. Snow levels plummet
late Thursday afternoon into Friday (Christmas Eve) with
increasing potential for travel disruption due to snow,
especially for the weekend.
More Detailed Overview:
Persistent anomalous ridge parked between the Bering Sea and the
Gulf of Alaska will help to keep a trough anchored near the West
Coast through much of the week and into next week. This setup will
facilitate rounds of cold, continental air diving southward into the
West, while also allowing broad swaths of subtropical moisture to
slide under the ridge into the West Coast.
* WEDNESDAY NIGHT INTO THURSDAY STORM *
- A broad moisture feed off the Pacific will combine with forcing
from an upper wave moving into the West Coast to intensify
already ongoing precipitation in the Sierra and NE CA. Shortwave
passage will also herald spillover into western Nevada. Possible
fly in the ointment...latest ensemble cluster analysis shows 35%
of the simulations with the trough (and cold air) placement far
enough south to drop the snow levels, but there are a couple
clusters showing a 'split' solution. While it's a low chance
scenario, if this occurs the best dynamics and forcing with the
shortwave would be targeted elsewhere and result in lower
QPF|Snow totals.
- SNOW: While there is still some variability with the snow
levels, areas above 6000 to 7500 feet from Lassen to Mono County
should plan on significant snow (1 to 3 feet). At Lake Tahoe
level there may be a wide range of eventual snow totals for this
Wed PM - Thurs time frame, with anywhere from only 5 to 14
inches possible. For example, the EC ensemble meteogram for KBLU
@ 5284 feet shows QPF values 1-3", but the snow is only 0-5".
For KTVL @ 6269 feet, QPF ranges from 1.5-3.5" and the snow in
the 15"- 25" range. Keep in mind these are not the exact
forecast values...this is simply to highlight the ranges in
variability for a small elevation difference AND it is only
looking at the EC ensemble solutions.
- WIND: Damaging wind scenarios remain in the minority amongst
ensemble guidance this morning. The arrival of heavier
precipitation should dampen the strongest winds and lessen the
duration as well. The ridge winds will be howling through the
event, honestly much of the week, but localized stronger wind
gusts may arise at wind-prone areas in the lee of the Sierra as
well. Primary impact of concern for now is the potential for
blowing snow in the eastern Sierra, especially near gaps along
Highway 395.
* THURSDAY NIGHT INTO FRIDAY: A break? *
- Snow levels will drop down to most valley floors with
accumulating snow 'down here' becoming more probable heading
into the holiday weekend. Simulations are showing the potential
for a short break in widespread precipitation for Thursday night
into Friday. During this 'break', the Sierra and mountain
communities may transition to light-moderate snowfall, but
western Nevada (5000 feet and below) may have to sit tight until
the weekend for actual snowfall accumulations.
* CHRISTMAS DAY THROUGH NEXT MONDAY STORM POTENTIAL *
- Another round of snow will be possible through the weekend as
colder shortwaves drop into CA and NV. It's too early to nail
down exact amounts, but we can say that major travel disruptions
are likely in western NV and the Sierra through the holiday
weekend! Unlike for the lower elevation, for the Sierra, we can
venture to say with some confidence that this setup will likely
drop several more feet of snowfall in the highest terrain with a
couple more feet possible down into the Lake Tahoe Basin and
perhaps 1-2 feet for the eastern Sierra along the Highway 395
corridor.
Hope you're all prepared! Tonight's storm kicks off a doozy of a
week.
-Edan
&&
.AVIATION...
Although chances for another bout of freezing fog falls off
considerably early this morning, increased southwest winds aloft
will bring periods of LLWS and moderate turbulence to the Sierra
and far western NV terminals today. Otherwise, VFR conditions
will continue for for all regional terminals through today.
Starting tonight, the first in a series of winter systems will
bring rounds of moderate to heavy mountain snow. KTRK and KTVL
could see -SN accumulating after 06Z Wed with periods of LIFR/IFR
conditions through Wednesday. Visibility will be diminished
greatly with mountain obscurations likely across the region. Light
to moderate precipitation that could see rain/snow transitions
will produce varying airfield conditions that fluctuate quickly
between MIFR/IFR at far western NV terminals (KRNO-KCXP-KMEV).
Flight conditions will also include in-cloud rime/mixed icing and
wind gusts that will create moderate to severe turbulence and LLWS
over Sierra terminals and KRNO. Later Thursday afternoon into
Thursday night, snow levels will drop to valley floors bringing
increased snow chances to all terminals.
-Amanda
&&
.REV Watches/Warnings/Advisories...
NV...Winter Weather Advisory from 7 PM this evening to 4 AM PST
Thursday NVZ002.
Winter Storm Warning from 4 AM Thursday to 4 PM PST Sunday
NVZ002.
CA...Winter Weather Advisory from 7 PM this evening to 4 AM PST
Thursday above 5000 feet in CAZ071.
Winter Storm Warning from 4 AM Thursday to 4 PM PST Sunday
CAZ071.
Winter Storm Warning from 4 PM Wednesday to 4 PM PST Sunday
CAZ073.
Winter Weather Advisory from 7 PM this evening to 4 AM PST
Thursday CAZ072.
Winter Storm Warning from 4 AM Thursday to 4 PM PST Sunday
CAZ072.
&&
For more information from the National Weather Service visit...
http://weather.gov/renoThe national radar mosaic for the moment the first event began.
9 heavy snow, 7 heavy rain, 3 high wind, 1 winter storm. Local standard time, as filed.
The public reported a 7 day storm total snow amount of 83 at Mammoth Mountain Ski Base and 78 at June Mountain Ski Base.
The public reported a 7 day storm total snow amount of 78 at Heavenly Ski Base.
The public reported a 7 day storm total snow amount of 132 1.0 mi SSW of the Northstar Ski Base.
According to the U.C. Berkeley Central Sierra Snow Lab, Lake Tahoe has seen a record-breaking amount of snow in December - 214 inches. The Sierra Snow Lab reported that the Dec 2021 snowfall was the third snowiest on record per tracking from the lab that started in 1970.
Trained spotter located 6.0 mi SSE of Susanville, CA in Lassen County reported 3.5 of wet snow at an elevation of 4800 .
CO-OP Observer, COCORAHS station (CA-MN-6), and mesonet sites reported heavy rain ranging from 0.55 -0.65 in Lee Vining and up to 2.00 at mesonet site (CRVC 1) 1.0 mi SSW of Crestview, CA.
Mesonet stations located at various locations around Meyers, CA reported heavy rain amounts ranging 2.0 to 3.0 from Fallen Leaf Lake to Lake Baron, CA.
CO-OP Observer station (VERC1) located 2.0 mi W of Verdi, NV (or 2.0 mi SSE of Dog Valley, CA) reported heavy rain amount of 2.07 .
Mesonet station (MTH03) located 1.7 mi S of Mammoth Mountain Ski summit reported a wind gust of 106 mph.
COCORAHS Station (CA-NV-51) located 1.6 mi N of Truckee, CA reported heavy rain amount of 2.45 .
COCORAHS station (CA-ED-20) located 4.9 mi SW of South Lake Tahoe, CA (or 2.0 mi NW Meyers, CA) reported heavy rain amount of 1.8 .
COCORAHS station (CA-MN-5), AWOS, and mesonet sites reported heavy rain ranging from 0.72 at Benton, CA (BETC1), to 1.16 from AWOS located at USMC MWTC Bridgeport, and 2.47 at the mesonet site (CRVC1) located 1.0 mi SSW of Crestview, CA.
The public reported 24hr heavy snowfall amounts ranging 31 -40 at Mammoth Mountain Ski Base.
Mesonet stations located 3.0 mi SSE of Frenchman Lake and 5.0 mi NNE of Cromberg reported heavy rain amounts of 1.24 and 1.74 respectively.
The public reported 24hr heavy snowfall amounts of 10 at Mammoth Mountain Ski Base and June Mountain Ski Base.
Mesonet station (TADC1) located 4.0 mi WNW of Truckee, CA reported wind gust of 66 mph.
Mesonet station (MTH03) located 1.7 mi S of Mammoth Mountain Ski summit and Mesonet station (SE089) located 1.3 mi SW of Conway Summit both reported a wind gusts of 98 mph.
A trained spotter located 5.0 mi WNW of Susanville, CA reported 24hr heavy snowfall amount of 25 with current snow depth of 37 .
The following information was included in High Impact Event report issued 12/26/2021 and 12/27/2021.
Interstate-80 was closed through at least mid-day Monday when the conditions were re-evaluated. Based on the heavy snow forecast Interstate remained closed until Tuesday with no specific estimated opening time. Virtually all trans-Sierra routes are closed due to snow and/or wind impacts - this is also unusual to have so many routes disrupted this long. Caltrans received email briefings from both WFO Reno and WFO Sacramento.
Southwest Airlines, the largest carrier in Reno, had cancelled all flights today and tonight (12/26/2021), due to wind concerns. Coordination with Reno Airport operations on snow and wind trends.
Accident involving 20-cars on Interstate 580 between Reno and Carson City with at least 6 injuries requiring hospitalization. Blowing slow occurring at the time of accident.
Highway 395 in the Eastern Sierra closed for prolonged periods, due to measured wind gusts near the highway of 85 to 98 mph, blowing snow, and low visibility. This is a major route between LA, Mammoth, and Reno.
All ski areas in the Tahoe region were closed due to dangerous conditions and high winds. Massive impacts likely to people on holiday who may now be stranded at these resorts possibly into Monday and Tuesday.
Several avalanche reports in the Eastern Sierra but no damage or injuries reported. One occurred near Alpine Meadows closing the only road in and out of the ski area.|An avalanche occurred in the Tahoe area, closing CA 89 which is the main route from Tahoe to I-80. This along with the continued hazardous snowfall and winds, had resulted in the closure of all ski areas in the Tahoe-Truckee region through Monday (12/27/2021).
The public reported 24hr heavy snowfall amounts 14 at Mammoth Mountain Ski Base and 22 at June Mountain Ski Base.
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, December 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: 992725, 992743, 992745, 992662, 992656, 992719, 992750, 992748, 992718, 992747, 992751, 992720, 992721, 992749, 992722, 992744, 992723, 992746, 992663, 992724.