A blast of frigid arctic air has descended over the western United States, toppling records far and wide as readings plummet to some 40 degrees below average for this time of year. Temperatures throughout much of the Rockies dipped below zero to start the week, falling as low as minus-29.2 in Potomac, Montana early Sunday – the coldest temperature ever observed this early in the season across the Lower 48.
The cold has helped whip up a significant winter storm, which is taking shape now from the Four Corners to the southern Plains. It’s dropping heavy accumulations of snow and ice as the frigid air plunges south in its wake.
Winter storm and ice storm warnings are up for most of Colorado, New Mexico, the Texas Panhandle and Oklahoma, while winter weather advisories stretch northeast into Kansas City towards the Iowa border. Behind the system, wind chills will drop to minus-25 in the Intermountain West Monday night.
Meteorologists sometimes refer to storms like this one as a kitchen-sink storm, a tempest that combines the worst of all seasons where different air masses collide.
Central Oklahoma is preparing for their worst ice storm since 2015, with the Oklahoma City metro area under an ice storm warning.
Flanking the shot of cold air and snow lays extreme wildfire danger on the West Coast, the result of cool air pushing across the slopes of the Sierra Nevada Mountains, warming, drying and accelerating downhill at speeds greater than 100 mph in some cases.
A sharp dip, or trough, in the jet stream across the West has allowed cold air to spill south into the western and North Central states, bringing frigid readings bordering on the extreme.
In Potomac, Montana, where the minus-29.2-degree reading was set, the Weather Service had predicted the location would hit minus-30, which would have been the Lower 48′s earliest minus-30-degree reading on record, which didn’t end up happening. Regardless, the ongoing cold is off the charts, with the air mass more typical of December or January than late October.
“I talked with a climatologist in Alaska,” Dickerson said. “He said that Potomac was the coldest. It’s truly remarkable. There’s no other way to describe it.”
Two out of the past three mornings have been among Missoula’s coldest three ever recorded in October, and more records will likely fall later in the week.
“I’ve been describing it as a once in a century event,” Dickerson said.
In addition to Sunday’s reading of nearly thirty below, a slew of other records have come crashing down courtesy of the early-season Arctic outbreak. Missoula set a record for their earliest zero-degree reading observed, hitting minus-7 on Monday morning. Anaconda, a town of 9,000 in western Montana, was forecast to drop to minus-23 degrees Monday morning; their previous record was 5 degrees.
Missoula also logged its eighth-biggest snowstorm on record, with a hefty 13.8 inches falling in just two days’ time.
It’s not just the Northern Tier that’s been dealing with record cold. Boulder, Colorado snagged a record Monday morning when they dipped to 5 degrees; the previous record for the date, set in 1997, was 13 degrees.
Accompanying the cold has been a batch of heavy snow that over the weekend plastered parts of the High Plains and Rockies. Denver hit 8 degrees early Sunday, and picked up just under three inches of snow. Boulder, tucked into the Foothills, wound up with more than a foot.
Despite the heaviness of the snow, Coloradans are no stranger to wintry weather in October. In fact, the 9.9 inches that fell in Boulder on Sunday doesn’t even claim a top spot for an October snowstorm.
Some of the snow did fall on the Cameron Peak and East Troublesome Fires, the state’s largest and second-largest wildfires on record. While that will bring about at least a temporary slowdown of the blazes, it is unlikely to completely extinguish them, especially since milder weather will follow this cold snap.
Farther south, almost the entire state of New Mexico was under a winter storm warning Monday, where heavy snow of a half foot or more is likely in the majority of locales. Higher elevations in the mountains could see 12 to 18 inches.
The snow had filtered into Texas following a bone-chilling “blue norther” cold front last week, with temperatures plummeting behind an Arctic cold front.