The calendar may have just turned to October, however, Winter Storm Atlas is poised to bring heavy snow to the northern Rockies, some snow even at lower elevations, and perhaps the season's first snow to parts of the Northern Plains.

As you can see in our snowfall forecast map at right, the heaviest snow accumulations from Winter Storm Atlas are expected to be over the highest elevations of southern Montana, Wyoming and far northern Colorado. More than a foot of total snow is likely over the Tetons, Bighorns and Beartooth Ranges of Wyoming and far southwest Montana, as well as the Black Hills of South Dakota and mountains of far northern Colorado.

With that said, significant accumulations, possibly more than six inches, are also expected over some lower-elevation cities including Casper, Cheyenne and Laramie, Wyo.

As the winter storm treks east, the forecast for snow in the northern Plains and Upper Midwest becomes more dicey, typical of an early or late-season event.

There's a chance that we could see rain change to or mix with snow at times from the Dakotas into western Nebraska Friday into Saturday. This will be dependent on how much cold air comes southward from Canada in combination with how much cold air the storm can generate itself.

If this happens, there is a potential for at least one, if not several inches of wet snow from western Nebraska into western and central South Dakota, and perhaps a small part of North Dakota.
If any snowflakes do fly through the air, it would be the first of the season for parts of this region, and would be among the earliest one-inch-plus snowfalls on record for locations such as Pierre, S.D.

If that wasn't enough, strong winds will pick up Thursday night, and continue through much of Friday and Friday night in these areas.

The combination of wet, heavy snow and strong winds will not lead to reduced visibility with local blizzard conditions in parts of Wyoming, the mountains of far northern Colorado and the Black Hills of South Dakota from late Thursday through Friday night.

In addition, the weight of wet snow and force from strong winds will lead to some downed trees or tree limbs, particularly on trees still yet to drop their leaves. Power outages will also be an issue in these areas.

http://www.weather.com/news/weather-winter/winter-storm-atlas-forecast-20131001