For the second time in two weeks, a powerful early-season winter storm is set to unleash double-digit snowfall totals across a wide swath of the northern Plains and Rockies through Friday. Heavy snow, strong winds and near-blizzard conditions are expected.
Winter storm warnings stretch from Wyoming and Montana through western Nebraska, then eastward into the Dakotas to the Canadian border.
The National Weather Service in Bismarck, N.D., is referring to the sprawling storm system as a “potentially historic October winter storm.”
What makes this storm so notable?
“I think, obviously, the magnitude of it, and it being the first storm of the season,” said Patrick Ayd, a meteorologist at the Bismarck NWS office. “It’s so early in the season. Normally we get to ease into things.”
Despite this, Ayd noted that the past five to 10 years have featured several bouts of deeper, early-season snow for the northern Plains, calling this event “not terribly unusual” in that sense.
Light to moderate snow was already falling across the hills and valleys of central and eastern Montana on Wednesday afternoon.
Things are expected to ramp up Thursday morning, when a stream of moisture-laden air from the south starts to kick in, acting as a conveyor belt to aid in snow production. As the storm system intensifies, and its trailing cold front crashes east, any rain in eastern North Dakota will flip to heavy, wet snow.
Snowfall rates of an inch or more per hour are expected at the height of the storm.
Meanwhile, winds near the low-pressure area’s “comma head” — the wraparound precipitation in the cold sector of a sprawling storm system, often shaped like a comma — could top 40 mph. Combine that with the moderate to locally heavy snow and it’s likely to produce whiteouts in spots.
The National Weather Service noted that the storm “may create blizzard conditions.”
All told, 6 to 8 inches, with localized snowfalls of a foot or more, are likely in eastern Colorado, Wyoming and central and eastern Montana — greatest on the east slopes leading up to the higher elevations. The same is true in extreme-northwestern Nebraska.
In western and central South Dakota, and central and eastern North Dakota, a widespread 10 to 14 inches is expected, with sporadic amounts topping 18 inches possible.
As the storm system pushes north into Canada over the weekend, a pinwheel of rain and snow showers is set to linger over the eastern Dakotas, Minnesota, Wisconsin and the Upper Peninsula of Michigan.
Although it may seem like an early onset, this part of the country is no stranger to prolific October snow.
Rapid City, S.D., picked up 19 inches on Oct. 4-5, 2013, and Bismarck saw 15.9 inches in late October 1991.