It’s the summer tourism season in Yellowstone National Park, but the memo hasn’t reached northwest Wyoming.
The National Weather Service issued a Freeze Watch on Tuesday for the entire Bighorn Basin through Wednesday morning with crop-killing sub-zero temperatures of 30 degrees and lower expected across the region.
A Winter Weather Advisory also is in effect for the eastern thrust of the Wind River Mountains from Dubois to Lander. As much as 3 to 7 inches of snow could fall in Shoshone National Forest and the east edge of Yellowstone National Park.
Meanwhile, a Winter Storm Warning has been issued for the Bighorn Mountains with as much as 6 to 9 inches of snow. This could impede travel on the Powder River and Granite Passes, which were recently reopened for the season.
Cold weather will hound northwest Wyoming over the next few days, something people should remember before planning a Memorial Day excursion into Yellowstone.
“Spring is kicking and screaming on the way out,” said Cowboy State Daily meteorologist Don Day. “The weekend weather has started to evolve, and it’s not nearly as good as it looked just a couple of days ago. Things are changing.”
Yellowstone Winter In Summer
Day said a persistently stormy weather system has been dominating the Northern Pacific for most of May. Every two days, that system has been sending cold fronts through northwest Wyoming, bringing colder temperatures and high-elevation snow.
“The one going through now is making it snow in the mountains,” he said. “There’s a break in the weather tomorrow, but there's another chance of rain and snow in Yellowstone and across the northern half of Wyoming from Thursday into Friday morning. Then there’s a break in the weather on Saturday, followed by another one that will be coming through on Sunday.”
At Old Faithful, the National Weather Service anticipates scattered rain and snow showers throughout the week and into the weekend. No snow accumulation is expected, but temperatures will remain below 50 degrees for the duration.
“You might see all seasons,” Day said. “Sun, rain, snow, thunder — all of those things are on the table up there, and the pattern doesn't settle down up there until after the weekend is over. Each of these waves will bring a chance to rain and snow to Yellowstone.”
Such conditions mean there’s a high chance of black ice on Yellowstone’s main roads, particularly overnight. Day noted that Togwotee Pass was covered with snow Monday night, so the same can be expected in and around Yellowstone.
“Freezing temperatures in the park and the mountains overnight still occur all the way into June,” he said. “That’s to be expected. But it's going to be cold enough that the mountain passes probably see the snow stick to the roadways.”
Bison roam the still snowy hills near Mammoth Hot Springs in Yellowstone National Park. (Andrew Rossi, Cowboy State Daily) 
Palette Spring at Mammoth Hot Springs in Yellowstone National Park. (Andrew Rossi, Cowboy State Daily)
Holiday Weekend From Frozen Hell
While the weeklong ripple effect of wet winter weather will primarily impact northwest Wyoming, the rest of the Cowboy State could feel the chill. Over the next week, overnight frost and gusty winds are expected throughout the state.
“We have three separate systems to deal with between now and Sunday,” Day said. “Depending on how quickly the Sunday pattern moves out, we could maybe salvage one day that of this weekend, but we'll have to see. The trend is going negative regarding the weather forecast for the holiday weekend.”
With Memorial Day less than a week away, Day knows everyone wants a warm, mild holiday weekend, especially if they plan to visit Yellowstone. But at this point, it looks like they’ll need to pack their cold-weather gear or at least have enough in the bank to buy a bison hoodie at the first gift shop they encounter.
“The biggest concern is keeping people in Yellowstone warm and dry,” he said. “If there's a day that this clears out, it won't be until Monday. But it's not looking very tourist-friendly at the moment.”
Andrew Rossi can be reached at arossi@cowboystatedaily.com.
