(CNN) Just days after the start of fall, parts of the Rockies may soon be blanketed under as much as five feet of snow.

A winter storm warning is in effect until Monday morning for portions of north central Montana, the National Weather Service said. It may amount to as much as 30 inches in lower elevations, but the mountains could see three to five feet.

Near blizzard conditions are possible, the weather service said.

Snow in September is not so uncommon for the area, said CNN meteorologist Ivan Cabrera, but the amount expected is.

"If the forecast pans out, this would rival or surpass the 1934 winter storm which was for many areas the top early-season snowfall event on record," Cabrera said.

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