The latest weather system will diagonally slice Wyoming with a blast of wintry weather this week. And this time, there will be enough cold and snow to stay.

The National Weather Service has already issued winter weather advisories and warnings for most of western and central Wyoming beginning 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 going on a slot machine where you get three sevens,” Cowboy State Daily meteorologist Don Day said. “It’s not a storm, but a combination of events where moisture and cool temperatures will be in the right place at the right time in those areas. So it’s a confluence of events working together.”

Diagonal strip

While the latest weather system will affect Wyoming overall, its biggest impact will be in the “strip” it creates as it moves across the Cowboy State. The system will start Monday night in the southwest and move into central Wyoming in the northeast 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, then go up through Lander and Riverton.

“Then it will move through Casper to Gillette and then to Rapid City. That line is the axis where the highest humidity will be.”

The heaviest impact could be between 36 and six inches of snow in lower elevation areas along the strip. And this time, Day said there will be enough snow to stick.

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

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

“That line is the axis of where the most moisture will be,” Day said. “About 75 miles on either side of the line will be the part of the state that will be most affected. The southeast and northwest corners will have an impact, but it won’t be as big as those areas on the line.”

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

Cold arrival

The input system is part of roller coaster weather that Wyoming is experiencing over the past few weeks, Day said. Short wet and cold periods have been followed by “recoveries” of warmer, drier days that feel more like the last days of summer than the first days of fall.

Day said there will be another comeback after the entry system passes. However, the warmer days in Wyoming will be on the decline, especially as the days get shorter.

“We’ll see more funnel systems come through in the first few weeks of November,” he said. “Recovery warmer temperatures won’t be nearly as fun as they have been here lately. This system will be followed by several funnel systems. It’s the start of a cooler trend that has more legs.”

Day took the opportunity to remind Wyomingites that daylight saving time is almost over. Clocks will go back one hour on Sunday at 2am local time.

That will add an hour of morning light. It also means sunset will be even earlier, so everyone should anticipate earlier evenings.

Daylight saving time will start again on Sunday, March 9, 2025.

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

Where and what to expect

When the next winter weather system arrives late Monday night, 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 hardest things will be in Evanston, Green River, Rock Springs, Lander, Riverton, Casper, Douglas, Buffalo, Gillette, Newcastle and Sundance,” he said. “Those are the places that will have the biggest impact.”

That forecast means sections of Interstate 80, 90 and most of I-25 could be slick with melted snow. Southeast Wyoming won’t be as affected by this system, but Day warned Cheyenne and Laramie residents to be careful when commuting on I-80.

“There will definitely be some impacts in Cheyenne and Laramie,” he said. “Between Laramie and Cheyenne, you have almost 8,000 feet on I-80. And then between Rawlins and Laramie, you’re right below 9,000 feet in some places. I think this catches a lot of out of state travelers. You don’t feel like you’re on a mountain pass, but you are.”

The rest of Wyoming can expect several inches of snow, strong winds and a steep drop in temperature. High temperatures will be in the 20s and 30s, and a weekend return to the 70s doesn’t seem likely.

Day warned Wyomingites to drive carefully in the coming days, especially in the afternoon. Then the roads tend to become dangerously slippery, especially at highway speeds.

“The time of day is really important,” he said. “A lot of accidents on icy roads tend to happen in the late afternoon and evening when the sun starts to go down and wet roads become icy, especially at higher elevations.”

Andrei Rossi can be contacted at [email protected].