Heavy Snow and High Wind in Montana, December 13 to 15, 2021

Name: Heavy Snow and High Wind in Montana, December 13 to 15, 2021
Start: 2021-12-13T08:45
End: 2021-12-15T08:00
Location: Montana

December 13 to 15, 2021 · NWS TFX · 5 events in 3 counties and zones

As an upper level trough moved across the area in mid-December, snow showers developed across Southwestern Montana, bringing snow to the area, especially across the higher terrain. While snowfall amounts were generally 1-3 inches across the lower elevations, some of the mountains received upwards of a foot of snow.

The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 5

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 TFX wrote it up.

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 Great Falls, MT wrote its last area forecast discussion before the first event at Dec 13, 4:39 AM MST, 4 hours 6 minutes earlier.

Area forecast discussion, Dec 13, 4:39 AM MST, 4 hours 6 minutes before

Area Forecast Discussion
National Weather Service Great Falls MT
439 AM MST Mon Dec 13 2021

...AVIATION SECTION UPDATED...

.SYNOPSIS...

Afternoon high temperatures will remain near to above seasonal
averages through Tuesday, before cooling below average for the
remainder of the week. Accumulating snow can be expected along the
Continental Divide and over the central and southwest Montana
mountains through Tuesday. By Tuesday night, an approaching trough
will bring some lower-elevation snow, followed by occasional hit-
and-miss snow showers through the remainder of the work week.

&&

.DISCUSSION...

Today through Wednesday...

Periodic snow showers continue through this morning along the
Continental Divide and parts of southwest and west-central Montana
today under an increasingly amplifying upper-level pattern as a deep
closed low moves south off the Pacific Northwest coast. The snow
will taper off a bit this afternoon into tonight as downstream
ridging strengthens a bit over central and eastern Montana. The
upper low then weakens into an upper trough and lifts out across the
area later Tuesday into Wednesday, pushing a cold front west to east
across the region bringing accumulating snow to much of the
mountains as well as the southwest valleys and central Montana. Snow
accumulations during the height of the event will favor the
southeastern one-third to one-half of the NWS Great Falls forecast
area, with accumulations generally in the 1 to 3 inch range for
lower elevations with up to 10 inches for the higher elevations for
the mountains surrounding the West Yellowstone and Big Sky areas.
Given the current elevation-based Winter Weather Advisory in effect
for southwest Montana with the current snow event, will hold off at
least another period before contemplating/issuing any additional
winter weather advisories for the Tuesday night & Wednesday snow
event.

Wednesday night through next Sunday...

An unsettled northwesterly flow aloft will help maintain below
normal temperatures and increased snow shower chances going for much
for the week. Thursday night looks to be the best time to see the
most widespread light snow chances as a fast moving trough passes
through the region. Longer range ensembles are in decent agreement
in bringing slightly milder temperatures, and increased surface
winds for the first half of next weekend, followed by another cool
down and mostly mountain snow shower activity. -RCG

&&

.AVIATION...

439 AM MST Mon Dec 13 2021 (13/12Z TAF period)

VFR conditions are generally expected for much of the TAF period.
However, Brief MVFR conditions will be possible through 13/16Z,
particularly for KHLN. Light snow chances and associated potential
for MVFR conditions then increase over the far southwest later
tonight. Also, there will be periods of mostly mid- and high level
cloudiness and mountain obscuration for much of the period. Strong
southwesterly flow aloft is expected to maintain surface wind gusts
to the 25 to 35 kt range at KEKS. Low level wind shear will also be
possible, mostly south of a KHLN to KLWT line. -RCG

Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  44  28  38  13 /  10  10  20  30
CTB  33  15  25   1 /  10  10  20  10
HLN  44  32  40  18 /  30  20  40  40
BZN  47  32  45  18 /  20  20  50  70
WYS  33  25  33  11 /  90  80 100  80
DLN  41  30  38  13 /  30  40  60  50
HVR  38  21  31   5 /  10   0  10  20
LWT  42  30  43  14 /  10   0  20  60

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 5 AM MST Tuesday Beaverhead...
Gallatin...Madison.

&&

http://www.weather.gov/greatfalls

In the hours before

Local storm report, Dec 13, 7:22 AM MST, 1 hour 23 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
722 AM MST MON DEC 13 2021

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

0540 AM     HEAVY SNOW       6 WNW WEST YELLOWSTONE  44.69N 111.22W
12/13/2021  M14.0 INCH       GALLATIN           MT   PUBLIC

            REPORT RELAYED VIA SOCIAL MEDIA. SNOWFALL
            SINCE 12/12.

&&

MOLDAN

Event by event

3 heavy snow, 2 high wind. Local standard time, as filed.

Heavy Snow, Gallatin

When: December 13, 8:45 AM MST to December 14, 8:45 AM MST
Where: Gallatin forecast zone
Reported by: COOP Observer

Co-op observer station wygm8 west yellowstone. the period of the heavy snow event was 24 hours.

Heavy Snow, Beaverhead

When: December 13, 11:00 AM MST to December 14, 11:00 AM MST
Where: Beaverhead forecast zone
Reported by: Mesonet

Estimated 11 inches of new snow in the past 24 hours at the lakeview ridge snotel.

High Wind, Gallatin

When: December 14, 4:00 AM MST
Where: Gallatin forecast zone
Measured: 54 kt (62 mph) measured gust
Reported by: Mesonet

Mesonet station gnfhy 10.7 w emigrant (avalanche).

Heavy Snow, Madison

When: December 14, 8:00 AM MST to December 15, 8:00 AM MST
Where: Madison forecast zone
Reported by: SNOTEL

Snowtel site reports 12 inches of snowfall in the previous 24 hours at clover meadow.

High Wind, Madison

When: December 14, 10:15 AM MST
Where: Madison forecast zone
Measured: 52 kt (60 mph) measured gust
Reported by: AWOS

Awos station keks ennis big sky awos.

What these are

Heavy Snow: Snowfall reaching the local warning threshold without the other hazards of a winter storm.
High Wind: Sustained non-thunderstorm winds of 40 mph or more for an hour, or gusts of 58 mph or more.

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

The same day elsewhere

Every storm in Montana in 2021 Every state in 2021 This day in weather history Warnings in Montana, 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: 996716, 996715, 996709, 996722, 996713.