The first day of fall isn’t for another week, but the first signs of winter can already be seen covering the highest points of Wyoming.
Drivers making the Monday morning commute over Togwotee Pass were greeted by a flurry of light, wet snow near Wind River Lake.
“It wasn't much, but the trees and grass had snow on them,” said Cowboy State Daily meteorologist Don Day. “The shorter days and longer nights are starting to add up, so you're getting cold enough at night and in the mornings for snow levels to get lower and lower.”
A dusting of snow has already been spotted in mountain ranges across western Wyoming, and between 1 and 6 inches of snow is expected to fall on the Beartooth Highway between Monday night and Wednesday.
There have already been forecasts for an early onset of winter in the Cowboy State. With snow falling before the first day of fall, is Wyoming skipping autumn in favor of a longer winter?
“Everybody would like a transition that's not abrupt and all at once, and that's kind of what's happening this week,” Day said.
September Snow
The snow falling this week is the result of a cooler system moving into Wyoming from the Pacific Northwest. It’s not strong or cold enough to impact the entire state, but the mountains will see some snow as it passes through.
“We’re almost in astronomical fall, but already in meteorological fall,” said Taylor Wittman, a meteorologist with the National Weather Service (NWS) office in Riverton. “With this cooler system coming in, it’s cool enough that people are seeing snow on mountain passes and highways.”
Wittman said this week’s cooler weather has the potential to go beyond the highest elevations of Wyoming. Snow could reach areas as low as 9,000 feet, which explains the Monday snowfall on Togwotee Pass.
However, getting snow in mid-September isn’t unusual. September has a history of being erratic in Wyoming, as chronicled by historical data collected and curated by the NWS.
“If you look at the record high and low temperatures for this time of year, you see record-highs in the 90s to almost 100 degrees, but you also see record-lows below freezing,” Wittman said. “September is the period when we get these big fluctuations in weather systems as the atmosphere starts to change from summer to winter.”
Day also said seeing mid-September snow on Togwotee Pass or the Beartooth Highway isn’t unusual. Almost a year to the day, a blizzard temporarily closed the Beartooth Highway on Sept. 13, 2024.
“We see a more significant shift in late September, but mid-September snow isn’t unusual at all,” he said. “The weather’s getting colder, and the past week has felt more like fall than summer, so the threat of a more significant snow event has increased.”
Not A Trend Setter
The snow that fell on Togwotee Pass on Monday morning melted before noon. The nights and mornings might be colder, but afternoon temperatures are still too warm for any snow to stick.
If the Beartooth Highway sees any snow this week, it won’t be enough to end the high-elevation highway’s summer season.
Meanwhile, there’s an infinitesimally small chance of snow below 9,000 feet.
“You have to get above probably 10,000 feet to see any small accumulations, and that’ll be just on the peaks of the mountains,” Wittman said. “We’re definitely seeing snow, but none of it is going to stick too well.”
Even if there won’t be any snow, the cooler system should bring good things to the rest of Wyoming. Wittman said the system is going to sit over the state for most of this week, bringing much-needed moisture to the lower elevations.
“That should drop some pretty good rain, especially across central, eastern Wyoming, and southeastern Wyoming at least through Wednesday,” he said. “It could even extend into Thursday.”
Meanwhile, the extended forecast looks more like summer than fall or winter. After a weekend warmup, the NWS’s Climate Prediction Center is anticipating above-average temperatures through the end of September.
Wittman said there’s a slight chance of more high-elevation snow in the extended forecast, but the lower elevations shouldn’t see any white stuff before the end of the month.
“A big, cooler system could develop in the next couple of days, but our models aren’t picking up anything (like that) at the moment,” he said. “They’re favoring above-average temperatures through the end of September, and there aren’t any indications of any significant snow in the lower elevations.”
While The Getting's Good
Neither Day nor Wittman was concerned about low-elevation snow before the end of September, especially with temperatures trending warmer through the end of the month. Still, Day sees this week’s high-elevation snow as a cautionary tale.
“I see the weather getting colder and the threat for a more significant event at the end of September and early October,” Day said. “From what I'm seeing, the last weekend of September is showing signs of getting cold enough for people to take notice, which means we’ll see a more significant shift.”
Day’s advice is simple: if you want to enjoy warmer weather in Wyoming, do it now.
“The next two weekends are when you really want to get out,” he said. “The weather is looking really nice for the next two weeks, but it’s already gotten cooler. If anyone was going to ask me when to get out and enjoy what’s left of summer and fall, this weekend is as good an opportunity as we’ll get before the shift.”
Andrew Rossi can be reached at arossi@cowboystatedaily.com.
