Snowstorm to create hazardous travel, threaten power outages in Rockies, High Plains this weekend

By Alex Sosnowski, AccuWeather senior meteorologist

October 12, 2018, 3:39:24 PM EDT

A southward thrust of cold air from Canada will set the stage for a far-reaching snowstorm over the Rockies and High Plains this weekend into early next week.

Snow will spread southward along a 1,000-mile-long swath of the Interstate-25 corridor, where a 24-hour temperature drop of 30 to 60 degrees Fahrenheit is anticipated.

The air will get cold enough to create slippery travel even outside of the high country and the passes from northern Montana to northern New Mexico and northwestern Texas. Motorists should expect wintry conditions along portions of I-70, I-80 and I-90.

Much to the delight of skiers, up to a foot of snow may fall on some of the eastern slopes of the Rockies.

Where leaves have not fallen off the trees over portions of the High Plains and foothills, there is the risk of tree limbs breaking and sporadic power outages.

Airline delays are likely at Denver and secondary hubs in the region, due to aircraft deicing operations that will evolve as the storm gets underway.

"While temperatures will initially be high enough for rain or a mix of rain and snow at the onset, the air will cool during the storm to allow a change to all snow," according to AccuWeather Meteorologist Ryan Adamson.

In some cases, the snow will stick to the roads, and in other cases, snow that initially melts on the roads may freeze, unless treated by ice-melting compounds.

"Snow will first spread over western and parts of central Montana during Friday night and Saturday," Adamson said.

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During Saturday, snow will continue to break out and/or advance southward across much of Wyoming. The snow is likely to reach Cheyenne, Wyoming, during Saturday evening.

In Colorado, snow or a rain and snow mix will break out in the north-central and northeastern counties during Saturday evening and spread southward Saturday night. During the same time, snow is forecast to cover the landscape in southwestern Nebraska and northwestern Kansas.

Accumulating snow is forecast in Denver from late Saturday night into Sunday. Travel to the afternoon NFL game between the Rams and Broncos may be difficult with a storm total of 3-6 inches anticipated with temperatures expected to be in the 20s much of the day.

Record low temperatures are forecast to follow the storm.

"A clearing sky and diminishing wind will set the stage for temperatures to dip into the teens and even the single digits over a broad swath of the Rockies and High Plains in the wake of the storm," Adamson said.

"Temperatures are forecast to dip to lower levels in Denver, than it has been thus far this autumn in Utqiagvik, Alaska," according to AccuWeather Senior Meteorologist Dale Mohler.

Utqiagvik, formerly known as Barrow, is on the northernmost tip of Alaska.

Up to a few inches of snow is forecast to fall on Colorado Springs and Pueblo, Colorado, as well as Garden City and Dodge City, Kansas, on Sunday.

Over the southern Plains, some of the cold air will catch up with trailing moisture left behind by Sergio.

A few inches of snow are possible in Las Vegas, New Mexico, and Dalhart, Texas, during Sunday night to early Monday morning.

Because the snow will initially be wet and clinging in nature, it will likely weigh down trees that are still fully leaved. Some branches may break, taking power lines with them.

Motorists should be prepared for icy spots as temperatures plummet during and after the storm.

As cold air continues to spread southward and eastward, temperatures will be slashed by 20-40 degrees over parts of central and southern Texas and the southern Plains by early next week.

For example, highs in the 80s to near 90 will be replaced with highs in the 50s and 60s in San Antonio, Austin, Brownsville and Houston, Texas.

Farther north, the air will reinforce the already chilly conditions over the northern Plains and Upper Midwest next week.

Early-season snow is no stranger to Denver and much of the Rockies and High Plains. Just several days ago, close to an inch of snow fell on Denver on Oct. 6 with 1-2 feet of snow falling on parts of the Rockies.

This is because of the widespread high elevation in the region. Many areas just east of the Foothills to the Rockies average about 5,000 feet above sea level.

Some of the biggest snowstorms have occurred in the autumn and spring in the region, and snowfall tends to fall on a fairly consistent basis from October through April at and above this elevation in the western United States, especially within and along the eastern slopes of the Rockies.