The latest weather system will move diagonally across Wyoming this week with a barrage of wintry weather. And this time there will be enough cold and snow to last.

The National Weather Service has already issued winter weather advisories and warnings for most of western and central Wyoming from Monday night through Wednesday morning. A slow-moving system will move from the southwest to the northeast of the Cowboy State, bringing the first heavy snowfall of the season to the Plains.

“This system is like a slot machine where you get three 7s,” said Cowboy State Daily meteorologist Don Day. “It's not a storm, but a combination of events where moisture and cold temperatures are in the right place at the right time in these areas. So it’s a confluence of events all working together.”

The diagonal stripe

While the latest weather system will impact Wyoming as a whole, its biggest impact will be on the “strip” created as it moves through the Cowboy State. The system will begin in the southwest Monday evening and move northeast across central Wyoming on Tuesday and Wednesday.

“It's not a perfect diagonal, but it's pretty darn close,” Day said. “If you were to draw a line, it would go from Salt Lake City to Evanston, Green River and Rock Springs and then go up through Lander and Riverton.

“Then it goes to Casper to Gillette and then to Rapid City. This line is the axis on which the most moisture is located.”

The heaviest impacts could occur between 3 and 6 inches of snow in low-lying areas along the strip. And this time, Day said, there will be enough snow to stick.

“It will be mostly snow, so it will be the first significant snow on the plains,” he said. “What's going to happen is the first inch or two will melt, but after that it'll stick pretty well.” I expect it will stick in a lot of areas, not just the lawns but the grass as well Sidewalk.”

There will be bursts along the edges of the “strip,” but the rest of Wyoming won’t see as much snow.

“This line is the axis where the strongest moisture is located,” Day said. “Approximately 75 miles on either side of that line will be the part of the state that will be hardest hit. The southeast and northwest corners will have impacts, but they will not be as large as the areas along the line.”

Measurable snow in the plains means there will also be significant amounts of snow in the mountains. The Unita, Bighorn and Wind River mountain ranges could get up to a foot of snow from this system, and Casper Mountain will likely be covered in white by the end of the week.

Cold is coming

The incoming system is part of The weather “roller coaster” that Wyoming has experienced in recent weeks, Day said. Short, wet, cold spells were always followed by warmer, drier days, which felt more like the last days of summer than the first days of autumn.

Day said there will be another surge after the new system is over. However, warmer days will decrease in Wyoming, especially as the days become shorter.

“We will see more funnel systems in the first few weeks of November,” he said. “Recovering from the warmer temperatures won’t be nearly as fun as it has been lately. This system will be followed by other funnel systems. It’s the start of a colder trend that’s gaining momentum.”

Day took the opportunity to remind Wyomingites that daylight saving time is almost over. On Sunday, clocks will go back one hour at 2 a.m. local time.

This brings an hour of daylight into the morning. It also means sunset will occur even earlier, so everyone should expect the earlier evenings.

Daylight saving time begins again on Sunday, March 9, 2025.

“We’re at a point in the calendar where warm weather is just getting harder to come by,” Day said.

Where and what awaits you

When the next winter weather system arrives late Monday evening, Day said Wyoming communities in the strip should expect to wake up to a white morning and potentially dangerous driving.

“If I were to name cities and towns, the heaviest stuff would be in Evanston, Green River, Rock Springs, Lander, Riverton, Casper, Douglas, Buffalo, Gillette, Newcastle and Sundance,” he said. “Those are the places that will see the biggest impact.”

This forecast means portions of Interstates 80, 90 and most of I-25 could be slick from melted snow. Southeastern Wyoming will not be as directly affected by this system, but Day warned residents of Cheyenne and Laramie to be careful heading to I-80.

“There will definitely be some impact in Cheyenne and Laramie,” he said. “Between Laramie and Cheyenne, it’s almost up to 8,000 feet on I-80. And then between Rawlins and Laramie, in some places you're just under 9,000 feet. I think this surprises a lot of out-of-state travelers. It doesn’t feel like you’re on a mountain pass, but it is.”

The rest of Wyoming can expect several inches of snow, blustery winds and a sharp drop in temperature. Highs will be in the 20s and 30s, and a rebound back into the 70s over the weekend appears unlikely.

Day warned Wyomingites to drive carefully over the next few days, especially in the afternoons. Then the roads tend to become dangerously slippery, especially at highway speeds.

“The time of day is really important,” he said. “Many accidents on icy roads tend to occur in the late afternoon and evening as the sun sets and wet roads become icy, particularly at higher elevations.”

Andrew Rossi available at [email protected].