Back-to-back winter storms will soon hit the Midwest and Northeast

It may still be fall, but two snowstorms will soon hit the Midwest and Northeast, making it look and feel more like winter.

After hitting Montana and Wyoming on Friday, the first storm will bring accumulating snow to places including Omaha, Des Moines, St. Louis, Chicago, Milwaukee, Indianapolis and Detroit from Saturday into Sunday. This will cause dangerous travel conditions across the nation’s midsection, including parts of Interstates 70 and 80.

The storm will bring more snow to northern Wisconsin and the Upper Peninsula of Michigan, where feet of snow already fell this week. It will also bring more snow to Minnesota, where state patrol reported hundreds of car crashes during a storm earlier this week.

The second storm will probably track further south and east, threatening to bring snow and ice to a corridor of the Midwest, Appalachians and Northeast from Monday to Wednesday – as some people return to work and school after the holiday.

This wintry jolt of weather comes as an unusual weather phenomenon – called a sudden stratospheric warming – unfolds miles above the North Pole. It is causing frigid air to flood southward across North America. When this cold air clashes with milder, moister air in the United States, storms can form.

While temperatures will be cold during Saturday’s central snowstorm, they will tumble markedly after it passes. A frigid air mass from Alaska will sweep from the Plains to the Northeast from Saturday to Monday, with around 21 million people forecast to experience temperatures in the single digits.

First storm system

Several major cities across the central United States will experience their first accumulating snow of the season on Saturday.

Here are forecasts for five places where the weekend storm will hit hardest.

Each forecast starts with a winter storm-impact rating – a subjective assessment of the severity of the conditions expected from the storm, with zero being the least impactful and 10 being the most.

St. Louis

Winter storm-impact rating: 6 out of 10

Wet snow will develop during the predawn hours on Saturday morning and could become moderate-to-heavy for a time. Although temperatures will probably be above freezing, snow rates of a half-inch per hour may cause roads and sidewalks to become snow-covered and/or slushy, with 2 to 4 inches of accumulation before snow changes to rain. Freezing temperatures for days after the storm will cause untreated surfaces to become icy.

Des Moines

Winter storm-impact rating: 8 out of 10

Much of Iowa will be in this storm’s sweet spot for heavy snow – on its northern flank where there’s plenty of cold air. Around Des Moines, it will probably start Friday evening, with roads quickly becoming snow-covered and slippery. Moderate-to-heavy wet snow will continue into Saturday night before ending with a total accumulation of 6 to 12 inches. Blustery conditions, especially on Saturday night, will cause blowing and drifting snow and the potential for power outages. Temperatures will dip into the single digits on Sunday night.

Chicago

Winter storm-impact rating: 8 out of 10

Snow will develop in the Windy City around daybreak on Saturday, falling moderately to heavily into the night and accumulating 6 to 10 inches, with some blowing and drifting. Freezing temperatures will allow snow to stick and for untreated surfaces to remain snow-covered and/or icy after the storm ends. Overnight lows will dip into the single digits on Sunday and Monday nights.

Milwaukee

Winter storm-impact rating: 8 out of 10

Snow will start on Saturday morning and become moderate-to-heavy, with the worst of the storm Saturday afternoon and evening. Local snow bands may be enhanced by the warm waters of Lake Michigan. Snow is forecast to accumulate 6 to 12 inches by Sunday morning, with gusty winds causing blowing and drifting of the snow, especially near the lakeshore. Low temperatures will dip into the teens for several nights after the storm passes.

Detroit

Winter storm-impact rating: 5 out of 10

Snow will reach Detroit on Saturday evening, with the core of the storm on Saturday night – somewhat reducing its impact. By Sunday morning, residents will be digging out from 3 to 5 inches of snow, which will also blow and drift in the wind. Above-freezing temperatures will initially help with melting, though freezing conditions may cause icy spots from Monday to Wednesday.

Second system

A second winter storm could spread snow from the Midwest to New England early next week.

Because the disturbance that will cause the storm to form is near Alaska early Friday, it will take another day or two for forecast details to solidify.

However, a swath of accumulating snow and/or ice is possible from Missouri to Ohio into the Appalachians from Monday into Tuesday – with the potential for disruptive, moderate-to-heavy snowfall across the interior Northeast from Tuesday into Wednesday.

Higher snowfall amounts are possible in the Northeast because a coastal low pressure system, called a nor’easter, may form as the system’s cold air collides with warmer waters of the Atlantic.

How close the potential nor’easter forms to the coast will influence temperatures and snowfall amounts.

For now, major cities will most likely deal with mixed precipitation or rain, but if the system tracks a bit further offshore, then places from Washington, D.C., to Boston could see their first accumulating snow of the season.