September snow, cold to plunge across Rockies early this week

Sept. 6 (UPI) -- A drastic temperature swing and a dose of early season snow will have residents from Montana to New Mexico wondering what month it is by Tuesday.

A storm is forecast to bring a mixture of rain and snow across the Intermountain West and the Plains Monday through Tuesday night, spreading precipitation from northern Montana to Texas.

Snow is forecast to begin falling in the northern Rockies of Montana and Wyoming on Monday, before extending southward through northeastern Utah, Colorado, and northern New Mexico into midweek.

Ski resorts in Montana have had a few snow showers already this year. Big Sky Resort in southwestern Montana got a few flakes on the last day of meteorological summer, Aug. 31.

"Snow is common for the northern Rockies in the month of September, but the earliest measurable snow accumulation on record for a place like Denver is Sept. 3," said AccuWeather Meteorologist Nicole LoBiondo.

With snow set to arrive in the greater Denver area early Tuesday, that's less than a week after the earliest snowfall on record.

A significant snowfall is in store above 7,000 feet, on average, from western Montana to Wyoming and Colorado. It is in this area that 6-12 inches of snow is forecast and an AccuWeather Local StormMax™ of 18 inches is possible.

With elevations of 5,000 to 7,000 feet from Montana to northern New Mexico, a few inches of snow can fall, especially on non-paved surfaces. But, overall, snowfall levels will tend to be lower across the northern part of the Rockies, amounting to more snow.

Elevations below 5,000 feet are forecast to see a few flakes, which at times are likely to be mixed in with rain. Perhaps enough snow could fall for a dusting of snow on non-paved surfaces, but any accumulations will likely be slushy.

Roadways are likely to initially be wet given the magnitude of the heat ahead of the storm. As the cold air arrives with the storm and the ground begins to cool, however, roads and sidewalks could turn slick early on Tuesday. Pedestrians and motorists alike should be aware of the risk for slippery travel.

The weight of the snowfall on fully leafed trees could cause limbs and branches to break. In addition to damage to trees, fallen limbs could also lead to more widespread power outages.

In addition to the snow, this storm will usher in a temperature swing of as much as 65 degrees Fahrenheit in less than 48 hours.

A dip in the jet stream will allow cold air from Canada to rush southward and bring record-challenging low temperatures in cities like Billings, Mont., Cheyenne, Wyo., and Denver.

After Denver set an all-time record high for September of 101 on Saturday, a strong cold front of the will help cold air to infiltrate the Colorado capital, bringing temperatures into the 30s Monday night.