The second major storm in 10 days will dump several inches to 2 feet of snow over the northern Rockies and shock areas farther to the east over the northern Plains with blizzard conditions.
The storm system will bring another round of early-season accumulating snow to nearly a half a million square miles of the interior United States, and, in some cases, the snow will fall less than 24 hours after temperatures hover in the 50s, 60s, 70s, and 80s F.
Commuters in the Denver metro area will experience quite a shock on Thursday morning. Following temperatures that rise well into the 70s to near 80 on Tuesday and Wednesday, Denver will be blasted with snow and frigid temperatures that plunge into the teens by Wednesday night into Thursday.
By Tuesday morning, significant snowfall was already sweeping into parts of Montana, AccuWeather radar indicated, along with gusty winds. The gathering storm has prompted a slew of winter storm warnings and watches in parts of six states.
Arctic air will charge southward at the same time a storm moves eastward from the Pacific Ocean over the northern Rockies and Plains during the middle and latter days of this week.
The arrival of the Arctic air and the strengthening storm will cause weather conditions to change rapidly, whether in the mountains, over the passes or on the Plains.
As temperatures plunge to the 30s, 20s and teens, any rain that falls during the onset of the storm will change to snow from north to south and from higher elevations to lower elevations in the region.
Motorists will be at risk from getting stuck as road conditions quickly transition from wet to slushy and snow-covered.
Travel along portions of Interstate 15, I-25, I-29, I-70, I-80, I-90 and I-94 will be difficult and dangerous. It is possible that travel on portions of some of these major highways is shut down for a time from mid- to late-week.
AccuWeather RealFeel® Temperatures will dip to 10 to 20 degrees lower than the actual temperature as gusty winds kick in during the storm.
With leaves still on the trees at intermediate and lower elevations, the clinging nature of the snow can weigh branches down and lead to sporadic power outages.
The storm will have two parts, the first of which will target the northern and central Rockies and High Plains. The second part will bring snow to not only the eastern and central portions of the Dakotas but western Minnesota, while it whips up blizzard conditions.
Heavy snow to fall on Montana, Idaho, Wyoming, and Colorado
Snow will spread southward across much of Montana and northern Idaho Tuesday night and reach central Idaho and much of Wyoming on Wednesday.
While less snow will fall from this storm when compared to the late-September storm over the northern Rockies and High Plains, accumulations are forecast to range from a few inches in parts of northern Idaho and the eastern parts of Montana and Wyoming to an AccuWeather StormMax™ of 24 inches over south-central Montana.
The greatest amounts of snow are likely to fall over the Elkhorn, Bighorn, Beartooth, Madison, and Absaroka ranges.
The storm from late September already brought one-quarter to one-half of the average seasonal snowfall in parts of the northern Rockies with the official start of winter still a couple of months away.
For example, Cut Bank, Montana, was blanketed by 18 inches of snow from the late-September storm alone and has an average seasonal snowfall of 34 inches.
The midweek storm will significantly add to the totals for the winter of 2019-2020.
For the Denver area, in addition to the dramatic temperature swing, this storm will bring the Mile High City its first snowfall of the season. Temperatures at the start of the day in Denver on Thursday are projected to be in the upper 20s with snow of varying intensity.
Second leg of storm to hit Dakotas and Minnesota as a blizzard
While much of the snow that falls over the Rockies and High Plains will be due to moist air flowing uphill, snow that falls and blizzard conditions that unfold farther to the east will be due to the strengthening nature of the storm itself.
Rain will mix with and change to snow from west to east from the central Dakotas to western Minnesota during Thursday to Thursday night.
However, the heaviest snow will thump in this area as the storm intensifies late Friday into Saturday.
A general 6-12 inches of snow will fall from western and central South Dakota to central and eastern North Dakota. An AccuWeather Local StormMax™ of 24 inches is in store for parts of central and eastern North Dakota.
In portions of the northern Plains, the visibility is likely to dip below one-quarter of a mile with frequent winds topping at 40 mph, which is the criteria for blizzard conditions.
Substantial blowing and drifting of snow is in store at the height of the storm Friday and in its immediate wake during part of this weekend.
The storm is forecast to bring a few inches of snow to northwestern Nebraska and western Minnesota.
In the wake of the storm, record low temperatures can occur over portions of the North Central states late this week and this weekend.
Related video: Winter is coming; snow starts falling at ski resort