Winter Storm in Idaho, December 13 to 14, 2021

Name: Winter Storm in Idaho, December 13 to 14, 2021
Start: 2021-12-13T21:00
End: 2021-12-14T17:00
Location: Idaho

December 13 to 14, 2021 · NWS MSO · 1 event in 1 county or zone

Heavy snow impacted the Camas Prairie, particularly Grangeville, from the evening of December 13th to December 14. A moist and unstable northerly flow focused the heaviest snow across Grangeville.

Where it happened

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.

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

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 1

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.

Heavy snow impacted the Camas Prairie, particularly Grangeville, from the evening of December 13th to December 14. A moist and unstable northerly flow focused the heaviest snow across Grangeville.

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 13, 1:33 PM PST, 7 hours 27 minutes earlier.

Area forecast discussion, Dec 13, 1:33 PM PST, 7 hours 27 minutes before

Area Forecast Discussion
National Weather Service Missoula MT
233 PM MST Mon Dec 13 2021

.DISCUSSION...Warm moist southwesterly flow has set up over the
Northern Rockies today and will persist throughout the night. The
warm air has finally mixed to the surface for locations south of
a line from Stevensville to Deer Lodge, so impacts from
precipitation should be minimal in these locations. While areas
that are hovering or still below freezing will have some impacts
as the next round of precipitation is expected to move through the
Northern Rockies right around sunset and the evening commute.
Multiple winter weather advisories have been sent out for the
areas with the greatest impact. The shower activity will mainly
linger across northwest Montana overnight. A cold front will begin
to make its way across the region late tonight into Tuesday
morning. This front will bring snow to much of north central Idaho
by midnight tonight with the Camas Prairie receiving at least 2
inches of snow. Lemhi county will also experience light snow
tonight through tomorrow, but they will have the addition of gusty
winds causing localized blowing the drifting especially south of
Leadore. Another area of concern is around Anaconda, where a snow
band could redevelop later tonight and linger through the morning
hours.

Drier air should move into the Northern Rockies behind this cold
front allowing for a decrease in precipitation Tuesday night into
Wednesday. Clearing skies and the colder air mass should allow
for some of the coldest temperatures experienced so far this
season.

Another weak low pressure system is anticipated to impact the
Northern Rockies on Thursday. This system has the potential of a
warm front followed by a cold front, so anticipate variable road
conditions.

The Northern Rockies will be under a transitory ridge on Friday
allowing for a dry period, but temperatures will be hovering at
seasonal readings. The models are indicating the potential for a
more robust system for the weekend. This system should bring
significant snow to the higher terrain with gusty westerly winds.
These winds will create downsloping effects in the broader
valleys.

&&

.AVIATION...A warm front moving across the region is causing light
precipitation across the region. Any locations with rain this
evening will quickly turn back to snow an hour or two after
sunset. Snow or rain and low ceilings are expected to impact all
area terminals tonight except KBTM. Timing of precipitation bands
is difficult, and short range models haven't been handling the
timing of bands very well. Using radar we've usually been able to
get half an hour to a couple hours lead time on IFR conditions.
And when VLIFR conditions occur, they generally last an hour or
less. Tomorrow morning a cold front will move through the region
and cause some snow showers with even KBTM being affected after
18Z.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory from 5 PM this afternoon to 5 PM MST
     Tuesday Butte/Blackfoot Region.

     Winter Weather Advisory from 8 PM this evening to 11 AM MST
     Tuesday Bitterroot/Sapphire Mountains.

     Winter Weather Advisory until 11 AM MST Tuesday
     Missoula/Bitterroot Valleys.

     Winter Weather Advisory until 11 AM MST Tuesday Lower Clark Fork
     Region.

     Winter Weather Advisory until 11 AM MST Tuesday Flathead/Mission
     Valleys.

     Winter Weather Advisory from 5 PM this afternoon to 11 AM MST
     Tuesday West Glacier Region.

     Winter Weather Advisory from 5 PM this afternoon to 11 AM MST
     Tuesday Kootenai/Cabinet Region.

     Winter Weather Advisory until 11 AM MST Tuesday Potomac/Seeley
     Lake Region.

ID...Winter Weather Advisory from 5 PM this afternoon to 11 AM MST
     Tuesday Eastern Lemhi County...Western Lemhi County.

     Winter Weather Advisory from 7 PM this evening to 10 AM PST
     Tuesday Northern Clearwater Mountains...Southern Clearwater
     Mountains.

     Winter Weather Advisory from 10 PM this evening to 10 AM PST
     Tuesday Lower Hells Canyon/Salmon River Region...
     Orofino/Grangeville Region.

&&

In the hours before

Local storm report, Dec 13, 4:52 PM PST, 4 hours 8 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
552 PM MST MON DEC 13 2021

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

0900 AM     SNOW             1 E WOODLAND            46.31N 116.06W
12/13/2021  M6.5 INCH        IDAHO              ID   COCORAHS

            COCORAHS STATION ID-ID-5 WOODLAND.

0800 AM     SNOW             GRANGEVILLE             45.93N 116.12W
12/13/2021  M5.2 INCH        IDAHO              ID   COCORAHS

            COCORAHS STATION ID-ID-10 GRANGEVILLE.

0800 AM     SNOW             GRANGEVILLE             45.92N 116.13W
12/13/2021  M4.2 INCH        IDAHO              ID   COCORAHS

            COCORAHS STATION ID-ID-1 GRANGEVILLE.

0800 AM     SNOW             3 SW OVANDO             46.99N 113.17W
12/13/2021  M2.5 INCH        POWELL             MT   COCORAHS

            COCORAHS STATION MT-PW-3 2 WSW OVANDO.

0700 AM     SNOW             3 WNW WEST VALLEY       46.17N 113.09W
12/13/2021  M2.3 INCH        DEER LODGE         MT   COCORAHS

            COCORAHS STATION MT-DL-1 7 NW ANACONDA.

0830 AM     SNOW             10 SSE OROGRANDE        45.57N 115.45W
12/13/2021  M2.1 INCH        IDAHO              ID   CO-OP OBSERVER

            CO-OP OBSERVER STATION DXEI1 DIXIE 1 N.

0800 AM     SNOW             1 E SEELEY LAKE         47.18N 113.46W
12/13/2021  M2.0 INCH        MISSOULA           MT   COCORAHS

            COCORAHS STATION MT-MS-26 1 E SEELEY LAKE.

0900 AM     SNOW             2 NW CLINTON            46.79N 113.74W
12/13/2021  M2.0 INCH        MISSOULA           MT   COCORAHS

            COCORAHS STATION MT-MS-22 1 NW CLINTON.

0700 AM     SNOW             5 SW PORTERS CORNER     46.20N 113.41W
12/13/2021  M2.0 INCH        GRANITE            MT   COCORAHS

            COCORAHS STATION MT-GT-3 7 WNW GEORGETOWN.

0700 AM     SNOW             EVERGREEN               48.22N 114.27W
12/13/2021  M1.4 INCH        FLATHEAD           MT   COCORAHS

            COCORAHS STATION MT-FH-29 EVERGREEN.

0800 AM     SNOW             5 E WEEKSVILLE          47.54N 114.89W
12/13/2021  M1.3 INCH        SANDERS            MT   COCORAHS

            COCORAHS STATION MT-SN-5 5 N PLAINS.

0700 AM     SNOW             2 E FLORENCE            46.63N 114.04W
12/13/2021  M1.3 INCH        RAVALLI            MT   COCORAHS

            COCORAHS STATION MT-RV-17 FLORENCE 1.8 ESE.

0700 AM     SNOW             TURAH                   46.84N 113.83W
12/13/2021  M1.0 INCH        MISSOULA           MT   COCORAHS

            COCORAHS STATION MT-MS-23 TURAH.

&&

The radar

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

Open the radar archive at this moment

Event by event

1 winter storm. Local standard time, as filed.

Winter Storm, Orofino / Grangeville Region

When: December 13, 9:00 PM PST to December 14, 5:00 PM PST
Where: Orofino / Grangeville Region forecast zone
Reported by: Law Enforcement
Coordinates: 46.259, -115.562 (the zone’s center; the record gives no point)

A foot or more of snow was measured in Grangeville, leading to power outages and school closures. Avista Utilities reported 4,504 customers without power. The Idaho County Sherriff's office received numerous calls for vehicle slide offs and 20 calls involving downed power lines and power poles.

What these are

Winter Storm: A storm that brought snow, sleet or freezing rain at warning levels, usually over several hours or days.

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

The same day elsewhere

Every storm in Idaho in 2021 Every state in 2021 This day in weather history Warnings 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: 997254.