After a string of 90-plus-degree days in early June, the last thing you’d expect to see in Wyoming’s forecast is a chance of snow.
Nevertheless, there’s a good chance of rain and snow showers in Yellowstone National Park between Tuesday night and Wednesday. Daytime highs on Wednesday will be in the high 40s at Old Faithful.
“The peaks will get glistened up with a little bit of white when the heaviest part of the storm comes through over the next 24 hours,” said Cowboy State Daily meteorologist Don Day.
Over the next two weeks, temperatures could drop between 15 and 20 degrees below average, or even lower. Day called it "an interesting pattern" that’ll put a dent in the sunny start of summer.
“This is just the continued weirdness that we've had since November,” he said. “It's summer's trying to start, but it just can't get going yet.”
A Cold Trough
The source of this unseasonable summer weather is what Day and other meteorologists are calling “a cold trough.” It’s part of the natural ebb and flow of ongoing weather systems.
“We had an upper-level ridge and high pressure overhead last weekend, which helped have those hot 90-degree temperatures,” said meteorologist Molly Gerhardt with the National Weather Service (NWS) office in Riverton. “This kind of pattern shift will have a trough, generally the opposite of a ridge, that will help keep temperatures on the cooler side.”
The cold trough will move from west to east over the next few days. Gerhardt anticipates the system will bring cooler temperatures and “some helpful moisture,” but not a lot of it.
“There isn’t an impressive amount of moisture with this system, but it is going to drop some rain, and perhaps some snow in those higher elevations of the Tetons and Wind River Mountains.”
Day agreed that there won’t be much moisture in his system, but the shift is significant. In his words, “the cool is coming.”
“This system is blowing up every seasonal forecast for June,” he said. “Whatever you’ve heard or seen about what’s happening in June, just scratch it.”
Unseasonable Start To Summer
Wyoming’s temperature will be on a bit of a roller coaster for the next week.
After Wednesday’s high-elevation snow, Wyoming will jump back into more summer-like temperatures.
“This cold front will drop temperatures 5 to 10 degrees below normal, but that won't last too long,” Gerhardt said. “We'll get back near to even above normal temperatures, 5 to 10 degrees above normal, by Friday.
By the end of the weekend, temperatures will dramatically shift again in the opposite direction. Day called them “remarkably cool” for mid-June.
“I'm looking at temperature anomalies as much as 20 degrees or more by Sunday and Monday,” he said. “That means take 20 degrees off what the average high is, so you could have daytime temperatures in the 40s and low 50s in Yellowstone.”
The NWS anticipates daytime highs in the 70s for the rest of Wyoming on Sunday and Monday.
That pattern could continue through the week. Gerhardt said the guidance being monitored by the NWS indicates “a pattern shift” toward cooler temperatures.
“Some outlooks are trending toward below normal temperatures, especially for the eastern half of the state, with maybe a slight uptick in precipitation,” she said. “That would be anywhere from the 60s to low 70s, which is generally below normal for this time of year.”
Day wanted Wyomingites to understand how baffling the next week will be across the state. It’ll be a constant back-and-forth that’s decidedly not summerlike.
We have this cool front coming through the next couple of days,” Day said. “There’s going to be a brief warm-up Friday and Saturday, then temperatures reverse and go right back down again starting Saturday night into Sunday, and then the coolness persists for most of next week. It’s blowing up the long-range forecast.”
Delayed Reaction
What stood out to Day about the short-range forecast was how it didn’t look like June. If anything, it looks like what May should have been.
While May brought much-needed precipitation to portions of Wyoming, the entire month was still drier than average for most of the state. The next week’s weather looks more like May than May did.
“Our weather’s behaving like it’s three or four weeks out of sync,” he said. “What we saw in parts of May was really what we should have but didn’t get in March and April, and now June is showing signs of what sometimes happens in May.”
The real question is whether that pattern will persist. Will July be more June-like?
Both Day and Gerhardt said it’s too early to say. Extended forecasts indicate a return to form with hotter, drier days by the end of June, but those same extended forecasts have been consistently wrong since November.
“From the NWS’s Weather and Climate Prediction Center, it looks like things will be trending back into those near-summer temperatures that we typically feel, if not above normal, by the end of June into early July,” Gerhardt said. “We’ll see how things pan out over the next couple of weeks.”
Day cautioned outdoor enthusiasts of all stripes to prepare themselves. Most people are prepared for overnight chills or a day of below-average temperatures, but the next two weeks will be beyond that.
“What's striking is that this will be multiple days of cooler weather,” he said. “We'll rebound by the end of the month, but we're definitely hitting a cool patch. If you're doing outdoor stuff, you need to be prepared for cool, wet weather in the middle of June.”
Andrew Rossi can be reached at arossi@cowboystatedaily.com.
