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One Tiny Snow Band Leads to Nearly a Foot of Snow in Montana

A few inches of snow in mid-December in Montana isn’t usually that big of a deal, except for one exceptional snow band that set up shop over the capital of Treasure State on Monday night.

Mostly light snowfall blanketed much of Montana with an early week storm, but one tiny, 20-mile wide band left the state’s capital, Helena, with 10 inches of snow while most surrounding areas saw 1-3″.

Likely aided by a howling jet stream overhead, a narrow band of heavy snow developed over the sixth-largest city in Montana around 4pm on Monday and lasted until around midnight local time.

Jet-induced ‘banding’ of snowfall is common with strong polar jet streams in the winter, resulting in narrow bands of intense, rapidly-accumulating snowfall. The ferocious winds, sometimes approaching 150 to 200 miles-per-hour (MPH) within the strongest wind belts, forces the air to go up over the mountains, creating a major ‘upslope’ component to snowfall, acting to ‘squeeze’ out all of the available moisture in the atmosphere due to the rapidly rising air. Also aiding the cause for higher accumulations was Helena’s bitterly cold temperatures on Monday and Monday night, with a high of just 12° on Monday afternoon and mostly single-digit readings through the duration of the event.

Local TV station KXLH reported several minor accidents and traffic was significantly slowed from the snowfall, but no serious accidents were reported.

More snow overspreads the region later this week, as a major Pacific storm spreads moisture north and east into the Bitterroot Mountains and western Montana, perhaps delivering more widespread double-digit snow totals.

Winter is here and it’s here to stay, especially in Helena.

For WeatherNation: Meteorologist Chris Bianchi

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