Winter Storm, North Rocky Mountain Front
- When
- December 20, 5:00 PM MST
- Where
- North Rocky Mountain Front forecast zone
- Reported by
- Department of Highways
MT DOT reported severe winter driving conditions along US-2 from Browning to Marias Pass.
Winter Storm in Montana, December 20, 2016
A low pressure system moved quickly east-southeastward from west-central British Columbia on the morning of Tuesday, December 20th and redeveloped over southern Alberta, in the lee of the Canadian Rockies, by Tuesday afternoon before moving farther to the east. Westerly and moist flow accompanying this system allowed upslope snow, heavy at times, to spill-over the Continental Divide and impact…
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 TFX wrote it up.
A low pressure system moved quickly east-southeastward from west-central British Columbia on the morning of Tuesday, December 20th and redeveloped over southern Alberta, in the lee of the Canadian Rockies, by Tuesday afternoon before moving farther to the east. Westerly and moist flow accompanying this system allowed upslope snow, heavy at times, to spill-over the Continental Divide and impact portions of the northern Rocky Mountain Front, including Marias Pass along US-2.
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 20, 5:00 PM MST, 0 minutes earlier.
Area forecast discussion, Dec 20, 5:00 PM MST, 0 minutes before
Area Forecast Discussion National Weather Service Great Falls MT 500 PM MST Tue Dec 20 2016 .DISCUSSION... Quick update as of 420 pm...Have increased snow/rain coverage across the area this evening associated with the passage of a cold front. Left PoPs after midnight as is. Coulston Today through Thursday...Snow continues over the Rocky Mountains and most of the Southwest MT ranges amid a moist westerly flow. Water vapor imagery and surface observations reveal a potent shortwave system over the southern Canadian Rockies, with lee side pressure falls over souther Alberta. The trailing surface front is moving through northern Idaho, and will be expected to emerge across the Rockies around 00Z this evening. Winds have been gradually strengthening today, but so far have remained below high wind criteria. However, the Alberta clipper system is forecast to intensify and strengthen the pressure gradient. Winds are forecast to increase near high wind criteria for a short time as the front moves across North-central MT from west to east this evening. Therefore, a high wind warning remains in effect starting at 4pm MST and continue through midnight. Conditions improve overnight, with very light orographic snow continuing in NW flow through Wednesday morning. Skies clear Wednesday and Thursday as dry air moves across the region. Breezy conditions continue with the strong westerly flow aloft. PN Thursday Night through Tuesday...This period continues to be marked by forecast model uncertainty for a strong Pacific shortwave trof coming into the West Coast late Fri. A consensus-type forecast of the varying model solutions indicates the leading edge of precipitation from this system should reach our region starting Sat morning and followed by the primary moisture plume Sat night through most of Sunday. That translates into a fairly steady period of light snow through the Christmas holiday weekend, with most locations receiving a few inches of accumulation before the system heads into the Upper Midwest states on Sun night. Expect mostly dry conditions on Mon and Tues, but our brief run of above-freezing temps comes to an end with the Christmas system, as a colder Canadian airmass settles into the state as the shortwave exits. High temps drop back to 20s on Sat and re && .AVIATION... /Updated 0000Z/ VFR conditions are expected for most of the period across the forecast area, unless otherwise mentioned. A shortwave trough with an associated cold front will move east across the area through 06Z. A band of showers associated with this system will affect the terminals through this time, bringing scattered rain and snow showers and occasional mountain obscuring MVFR conditions. The band is currently over a line from Chester southwest to Dillon, over KGTF and KHLN. This band will move into the KHVR/KLWT/KBZN areas through 03Z, then out of the area by 06Z. A northwest flow aloft will follow in the wake of this system, keeping a chance of showers over the Rocky Mountain Front, but bringing clearing skies elsewhere. Strong winds associated with the frontal passage will bring winds of 20 to 35 kt with gusts of 45 to 60 kt to much of the area through 06Z, but they will decrease from the west overnight. Coulston && .PRELIMINARY POINT TEMPS/POPS... GTF 23 32 21 34 / 60 0 0 0 CTB 22 32 17 33 / 30 0 0 0 HLN 17 31 8 30 / 70 10 0 0 BZN 12 28 6 29 / 30 10 0 0 WEY -5 21 -12 21 / 80 30 0 0 DLN 8 26 4 26 / 30 10 0 0 HVR 19 32 19 36 / 10 10 0 0 LWT 19 30 17 35 / 40 10 0 0 && .TFX WATCHES/WARNINGS/ADVISORIES... High Wind Warning until midnight MST tonight Cascade... Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton... Judith Basin...Liberty...Toole. Winter Weather Advisory until 11 PM MST this evening Beaverhead...Central and Southern Lewis and Clark...Gallatin... Jefferson...Madison...Southern Rocky Mountain Front. Winter Storm Warning until 11 PM MST this evening above 5000 feet for Northern Rocky Mountain Front. Winter Weather Advisory until 11 PM MST this evening below 5000 feet for Northern Rocky Mountain Front. && weather.gov/greatfalls
Event by event
1 winter storm. Local standard time, as filed.
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
More
Every storm in Montana in 2016Every state in 2016This day in weather historyWarnings in Montana, December 2016
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: 663148.