A strong pressure gradient set up along the Rocky Mountain Front as an upper level ridge moved into the area. This would result in gusty winds along the Rocky Mountain Front, which would combine with freshly fallen snow to result in areas of blowing snow.
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 TFX wrote it up.
A strong pressure gradient set up along the Rocky Mountain Front as an upper level ridge moved into the area. This would result in gusty winds along the Rocky Mountain Front, which would combine with freshly fallen snow to result in areas of blowing snow.
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 24, 8:28 AM MST, 1 hour 54 minutes earlier.
Area Forecast Discussion National Weather Service Great Falls MT 828 AM MST Thu Dec 24 2020 .UPDATE... High clouds are moving across the region on a northwesterly flow aloft. Fog is present this morning around West Yellowstone. Drifting snow continues in gusty winds close to the Northern Rocky Mountain Front. All these elements are addressed in the forecast, so updates will not be posted this morning. && .SYNOPSIS... An upper level high pressure ridge moving into the region will maintain dry and relatively mild conditions through Christmas Day. A Pacific weather system will bring some light snow to the area at times this weekend with temperatures cooling back to near seasonal averages by Sunday. && .AVIATION... 425 AM MST Thu Dec 24 2020 (24/12Z TAF period) Upper level ridge of high pressure centered over the Pacific NW drifts east across the region through Friday for continued dry NW flow aloft and VFR conditions at all sites. Scattered high level cloud-cover spilling over the ridge increases tonight through tomorrow. Gusty SW surface winds at most N-central MT sites continue today before decreasing some tonight, while winds in broader SW MT valleys remain light. Hoenisch Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PREV DISCUSSION... /ISSUED 425 AM MST Thu Dec 24 2020/ Upper level ridge progresses east into the Northern Rockies today and across the region tomorrow for dry and unseasonably mild conditions through Christmas Day. Little cloud-cover today will give way to some increasing high level clouds tonight through Friday as some upper level moisture moves through the ridge. A strong surface pressure gradient remains in place along the east slopes of the Rockies today for continued gusty winds across western and SW portions of north-central MT with strongest gusts along the immediate east slopes of the Rockies. Ongoing blowing/drifting snow over western portions of Glacier county is expected to continue through this morning. Pressure gradient weakens some later today through Friday with winds decreasing slightly but remaining fairly breezy across north-central MT. This and warming temperatures should bring an end to much of the blowing/drifting snow in western Glacier county by this afternoon. A Pacific weather system moving onshore Friday night will spread moisture into the region Saturday and Sunday with temperatures cooling back to near seasonal averages by Sunday as well. The main dynamics and moisture with this system move by to the south of the area but expect some orographically driven snow favoring the mountains and parts of SW MT early Saturday, followed by better chances for some light snowfall further north across north-central MT Saturday night into early Sunday as surface low pressure drifts south and flow aloft turns more northwesterly. Total snow amounts Saturday and Sunday look to be around an inch or less for most lower elevation sites with 1-3 inches in the mountains. A split flow pattern develops early next week with the next Pacific system tracking south through Great Basin and relatively light flow aloft over the Northern Rockies and MT. This will maintain temperatures near seasonal averages with dry conditions likely to persist through at least the first half of the week. Another Pacific system looks to arrive by Thursday or Friday of next week though there is a fair amount of spread among forecast models with the details of its track and moisture impacts to the region. Hoenisch && .PRELIMINARY POINT TEMPS/POPS... GTF 47 30 46 27 / 0 0 0 0 CTB 44 26 40 23 / 0 0 0 0 HLN 39 18 39 22 / 0 0 0 0 BZN 37 10 39 17 / 0 0 0 0 WYS 22 -8 30 7 / 0 0 0 0 DLN 34 13 36 20 / 0 0 0 0 HVR 44 25 41 22 / 0 0 0 0 LWT 47 25 47 24 / 0 0 0 0 && .TFX WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 2 PM MST this afternoon Northern Rocky Mountain Front. && http://www.weather.gov/greatfalls
2 high wind. Local standard time, as filed.
Sustained winds at 48 mph at time of gust. blowing snow observed on web cam. mesonet station mtbrn two medicine bridge (mt dot).
Mesonet station delmt dellwo (mcscn).
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2020Every state in 2020This day in weather historyWarnings in Montana, December 2020
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: 928378, 928379.