Idaho, 2021

Heavy Snow and Strong Wind in Idaho, December 10 to 11, 2021

December 10 to 11, 2021 · NWS MSO · 2 events in 2 counties and zones

Strong southerly winds developed in Grangeville on December 11th as a Pacific cold front moved into eastern Oregon and Washington. Peak wind gusts in excess of 50 mph were observed, with limited damage to property and power infrastructure.

Where it happened

Every event with a place to put it; 2 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

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The toll

Deaths
0
Injuries
0
Property damage
$13,000
Crop damage
None recorded
Events
2

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 MSO wrote it up.

Strong southerly winds developed in Grangeville on December 11th as a Pacific cold front moved into eastern Oregon and Washington. Peak wind gusts in excess of 50 mph were observed, with limited damage to property and power infrastructure. Heavy snow impacted the northern Clearwater Mountains, leading to areas of power outages.

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 Missoula, MT wrote its last area forecast discussion before the first event at Dec 10, 2:07 AM PST, 6 hours 38 minutes earlier.

Area forecast discussion, Dec 10, 2:07 AM PST, 6 hours 38 minutes before
Area Forecast Discussion
National Weather Service Missoula MT
307 AM MST Fri Dec 10 2021

...HEAVY SNOW IN NORTHWEST MONTANA AND THE CLEARWATER MOUNTAINS IN
IDAHO THIS WEEKEND...
...STRONG WINDS IN GRANGEVILLE AND THE CAMAS PRAIRIE SATURDAY...

.DISCUSSION...Scattered snow showers have again brought light snow
accumulations to the mountains and valleys of western Montana and
north-central Idaho overnight. Expect to experience isolated
slick spots on area roadways in the valleys, particularly west-
central Montana, and snow covered roads over Lookout and Lolo
Passes. Plan accordingly and check area road conditions before
heading out this morning.

The high impact weather disturbance that we have been advertising
is still on track for this weekend, with little changes from the
past 24hrs. On Saturday, a trough of low pressure will deepen off
the coast off the Pacific Northwest, allowing for a strong
southwest flow to develop over the Intermountain West. As a
result, an Atmospheric River associated with a very strong upper
level jet stream in excess of 150 mph, will move over the Northern
Rockies. This will bring strong winds to the higher terrain,
along with significant snow accumulations, and strong winds to the
Camas Prairie.

First, the Camas Prairie will see strong southerly winds
developing Saturday morning, and continuing through the afternoon.
Sustained winds of 30 to 40 mph with gusts up to around 60mph, may
create power outages and downed trees in Grangeville and the
Camas Prairie.

Strong winds are also expected in the mountains of western
Montana and north-central Idaho, where winds in excess of 50 mph
will be common. The highest peaks of northwest Montana along the
Idaho border and the Continental Divide near Glacier National Park
may see wind gusts approaching 70 mph.

Along with the wind, will come snow. The mountains of northwest
Montana, and the Clearwater Mountains of Idaho will likely see
snowfall amounts of 1 to 2 feet Saturday through Sunday. Lookout,
Lolo, and Marias Passes are expected to see around a foot,
possible more during this period. The valleys of extreme northwest
Montana (Troy, Libby, and the Yaak Region), could see significant
snow accumulations as well. Though with an Atmospheric River,
often comes with rising snow levels. So the valleys will see
periods of snow changing to rain in the afternoon Saturday and
Sunday, then changing back to snow in the evenings. This could
limit some of the accumulations. Having said that, this storm
system is likely to bring the highest snow totals to the region so
far this season. There is roughly a 70-75% chance for 6 inches of
snow in a 48hr period, and a 50% chance of 8 inches of snow. If
you plan to travel over area passes or throughout northwest
Montana this weekend, keep up to date on the area forecast, as we
do have a number of Winter Storm Watches in place for the areas
mentioned above.

Details on the Winter Storm Watches and the High Wind Watch, can
be found by visiting our webpage at www.weather.gov/missoula.

The active winter pattern is expected to continue into next week,
though the strength of the next weather system isn't expected to
be as strong as the weekend storm. However periods of valley
snowfall is expected, along with a building mountain snowpack.

&&

.AVIATION...Convective snow showers continue to develop and move
over west-central Montana and north-central Idaho this morning.
This has brought light snow accumulations KMSO and expected to see
a couple more round of light snowfall through 10/1500Z this
morning. Snow showers will slow diminish through the day today,
and will likely remain confined to area mountains this afternoon.
Expect periods of mountain obscurations throughout the day across
the Northern Rockies. KBTM will see increasing westerly winds this
afternoon with gusts up to 20kts around 10/1800Z, continue through
10/2300Z. Strong winds are expected for all aviation sites
Saturday as a 145kt jet stream enters the region.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory until 9 AM MST this morning
     Missoula/Bitterroot Valleys...Potomac/Seeley Lake Region.

     Winter Storm Watch from late tonight through late Saturday night
     Lower Clark Fork Region.

     Winter Storm Watch from late tonight through Sunday morning West
     Glacier Region.

     Winter Storm Watch from late tonight through late Saturday night
     Kootenai/Cabinet Region.

     Winter Weather Advisory until 9 AM MST this morning
     Bitterroot/Sapphire Mountains.

ID...Winter Weather Advisory until 8 AM PST this morning Northern
     Clearwater Mountains...Southern Clearwater Mountains.

     High Wind Watch from Saturday morning through Saturday evening
     Orofino/Grangeville Region.

&&

In the hours before

Local storm report, Dec 10, 6:58 AM PST, 1 hour 47 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
758 AM MST FRI DEC 10 2021

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

0757 AM     SNOW             1 S CLINTON             46.75N 113.71W
12/10/2021  M2.5 INCH        MISSOULA           MT   TRAINED SPOTTER

            0.16 OF SNOW WATER EQUIVALENT. 15.6 TO 1
            RATIO. FELL SINCE 4 AM THIS MORNING.

&&
Local storm report, Dec 10, 6:59 AM PST, 1 hour 46 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
759 AM MST FRI DEC 10 2021

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

0700 AM     SNOW             3 ENE BIGFORK           48.07N 114.01W
12/10/2021  M1.2 INCH        FLATHEAD           MT   COCORAHS

            COCORAHS STATION MT-FH-16 2 E BIGFORK.

&&
Local storm report, Dec 10, 7:21 AM PST, 1 hour 24 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
821 AM MST FRI DEC 10 2021

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

0800 AM     SNOW             3 WSW RIGGINS           45.41N 116.38W
12/10/2021  M2.4 INCH        IDAHO              ID   COCORAHS

            COCORAHS STATION ID-ID-9 3 W RIGGINS THIS IS
            THE 1ST MEASURABLE SNOWFALL BESIDES THE
            TRACE THAT WAS REPORTED ON NOV 17.

&&
Local storm report, Dec 10, 7:43 AM PST, 1 hour 2 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
843 AM MST FRI DEC 10 2021

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

0700 AM     SNOW             2 E SEELEY LAKE         47.18N 113.44W
12/10/2021  M4.2 INCH        MISSOULA           MT   COCORAHS

            COCORAHS STATION MT-MS-18 2 E SEELEY LAKE
            0.34 INCHES OF SNOW WATER EQUIVALENT.

&&
Local storm report, Dec 10, 7:44 AM PST, 1 hour 1 minute before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
844 AM MST FRI DEC 10 2021

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

0800 AM     SNOW             PIERCE                  46.49N 115.80W
12/10/2021  M3.0 INCH        CLEARWATER         ID   CO-OP OBSERVER

            CO-OP OBSERVER STATION PIRI1 PIERCE.

&&
Local storm report, Dec 10, 7:46 AM PST, 59 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
846 AM MST FRI DEC 10 2021

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

0700 AM     SNOW             4 NNE LOLO              46.81N 114.05W
12/10/2021  M3.5 INCH        MISSOULA           MT   NWS EMPLOYEE

&&

The radar

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

Open the radar archive at this moment

Event by event

1 strong wind, 1 heavy snow. Local standard time, as filed.

Strong Wind, Orofino / Grangeville Region

When
December 10, 8:45 AM PST to 11:17 PM PST
Where
Orofino / Grangeville Region forecast zone
Measured
39 kt (45 mph) measured gust
Property damage
$13,000
Reported by
Law Enforcement
Coordinates
46.259, -115.562 (the zone’s center; the record gives no point)

Wind gusts in excess of 40 mph were observed in Grangeville from the morning to late evening hours of December 11th. The Idaho County Sheriff's Office reported several cable lines, trees, and a power pole fell down due to strong winds, leading to multiple traffic hazards.

Heavy Snow, Northern Clearwater Mountains

When
December 11, 4:00 AM PST to 1:00 PM PST
Where
Northern Clearwater Mountains forecast zone
Reported by
Public
Coordinates
46.674, -115.657 (the zone’s center; the record gives no point)

Heavy snow, with rates in excess of one inch per hour, was observed in Elk River, Grangemont, Headquarters, and in higher elevations areas of the northern Clearwater Mountains. One to two feet of snow was measured by area SNOTEL sites, with nine inches of snow being reported in Elk River. 264 residents in Elk River lost power, likely due to snow loading.

What these are

Strong Wind
Non-thunderstorm winds below high wind criteria that nonetheless caused damage or casualties.
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 Idaho in 2021Every state in 2021This day in weather historyWarnings in Idaho, December 2021

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: 997237, 997241.