A strong and steady jet stream stalled over the region. A few scattered showers and a favorable atmosphere allowed those stronger winds from aloft to reach down to the surface in southwest Phillips Counties.
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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 GGW wrote it up.
A strong and steady jet stream stalled over the region. A few scattered showers and a favorable atmosphere allowed those stronger winds from aloft to reach down to the surface in southwest Phillips Counties.
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 Glasgow, MT wrote its last area forecast discussion before the first event at Dec 22, 9:22 AM MST, 2 hours 17 minutes earlier.
Area Forecast Discussion...CORRECTED National Weather Service Glasgow MT 922 AM MST Tue Dec 22 2020 .DISCUSSION... Didn't make too many changes, just tweaked things toward going model guidance. Look for the strongest winds to hit most late this afternoon/evening then winds diminish from NW to SE late tonight. TFJ Previous Discussion... High Wind Warning has replaced the High Wind Watch for this afternoon and overnight. Upper trof moving into the northern Rockies with surface low spinning up along the Alberta/Montana border this morning. Most of the warm frontal precipitation has lifted into North Dakota or Saskatchewan, with clear skies over much of northeast Montana. Some low cloud or fog lingers in Phillips county but seems to be dissipating. Low will track east along the international border into North Dakota today. Strong cold air advection, high lapse rates and tight pressure gradient will help bring mid-level winds of 50-60kt down to the surface through the afternoon and overnight hours, so upgrading to high wind warning seemed warranted. Wrap around precipitation mainly in the form of snow will also help drag the stronger winds down. Snow amounts not expected to amount to much but visibility may be reduced by wind driven snow at times. Conditions will slowly improve from the northwest early Wednesday morning. Colder air will linger on Wednesday even as upper ridge begins to rebound over the west. Temperatures will then moderate into the end of the week. A shortwave trof pushes through the ridge over the weekend with the potential for some light precipitation and temperatures dropping closer to normal. RAE && .AVIATION... VFR to MVFR. A couple cold fronts will move through today. The first one will switch winds around toward the West then the second push will come in late this afternoon from the North/NW. Expect sudden wind direction changes with speed surges with these fronts today! Otherwise, LLWS is expected ahead of the fronts, with winds mixing to the surface behind the front. Flight conditions will also lower as low clouds and snow move into the region behind the front. Conditions will slowly improve Wednesday morning. TFJ && .CLIMATE... December 2020 is shaping up to be one of the warmest for northeast Montana. For more information, visit our website and click on Climate. We'll also pass some of this information on our Facebook and Twitter pages over the coming days. TFJ && .GLASGOW WATCHES/WARNINGS/ADVISORIES... High Wind Warning until 11 PM MST this evening for Central and Southeast Phillips...Central and Southern Valley...Garfield... Northern Phillips...Petroleum...Southwest Phillips. High Wind Warning until 5 AM MST Wednesday for Dawson...McCone... Prairie...Wibaux. High Wind Warning from 2 PM this afternoon to 5 AM MST Wednesday for Daniels...Eastern Roosevelt...Northern Valley...Richland... Sheridan...Western Roosevelt. && weather.gov/glasgow
The national radar mosaic for the moment the first event began.
1 high wind. Local standard time, as filed.
At the Malta South US-191 DOT site (MTMAL), short peak wind gusts of 58 mph were recorded in the late morning and early afternoon on the 22nd.
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: 934936.