While Wyomingites may wonder why the state’s climate suddenly has the temperament of a moody teenager, quickly shifting from heavy, wet snow to record-breaking temperatures, meteorologists say the state has always been subjected to what they describe as “roller coaster” weather in May.
Cowboy State Daily meteorologist Don Day said these week-to-week weather changes are part of the phenomenon he affectionately dubbed “Moody May."
“May is very susceptible to mood swings,” Day said. “In less than a week, we've had a snowstorm, funnel clouds, severe thunderstorm warnings, and record-breaking high temperatures.
While it may be normal for May to be “moody,” this past week may seem more like a temper tantrum swinging from extremes.
By Wednesday, Day said many places are expected to cross the 90-degree threshold for the first time this season. By Sunday, it could be snowing in the mountains.
And there could even more changes on the way.
Warm Wave
Less than a week ago, Cheyenne received an inch of liquid water from rain and snow, while temperatures statewide dropped into the 30s and 40s.
On Monday, Cheyenne’s daytime high was 82 degrees, and that wasn’t even the warmest spot in Wyoming thar day.
“Lander’s high-temperature record for May 11 is 84 degrees, set in 1940,” said meteorologist Adam Dziewaltowski with the National Weather Service (NWS) office in Riverton. “We’re currently forecasting a high of 85 degrees in Lander today.”
Casper’s record high for May 11 was 83 degrees, also set in 1940. Dziewaltowski said Casper’s high on Monday was expected to reach 84 degrees, breaking that 86-year-old record.
This is the beginning of a warm weather wave that’ll cover Wyoming this week. It'll be warmest on Wednesday, with daytime highs in the high 80s.
“Places like the Bighorn Basin could get into the mid-90s on Wednesday,” Dziewaltowski said. “Those temperatures could be flirting with monthly high-temperature records.”
Dziewaltowski said extreme swings can happen this time of year, but that comes with a caveat.
“What’s unusual is that it’s a lot warmer earlier than we expected,” he said. “It's not out of the ordinary to swing between warm and cold temperatures in May, but the temperatures are higher than usual.”
Moody May
“Like a teenager, May is moody,” Day said. “When you get into this time of year, you have these battles of air masses. So last week, Canada won. This week, the deserts won. That’s how you expect the pendulum to go back and forth as the seasons are trying to change.”
While acknowledging the potentially record-breaking high temperatures this week, both Day and Dziewaltowski said Wyoming isn’t “locked into” an extended period of warm, dry temperatures.
“We have a pretty big warmup this week, followed by a big wave of cooler air coming in behind it by the weekend,” Dziewaltowski said. “It's not out of the ordinary to go from cold temperatures and snow to hot, dry weather. I’d say that’s the Wyoming norm.”
After reaching or exceeding 90 degrees by Wednesday, the NWS’s extended forecast anticipates daytime highs in the high-50s to mid-60s by Sunday, with a slight chance of rain and snow showers in some spots.
That switch isn’t surprising to long-time Wyoming meteorologists.
“If you look at the climatological history of this time of year, May is known for heavy, wet snowstorms,” Day said. “That's why I use the teenager analogy. The weather is all over the board. May is when Wyoming starts to get severe weather.”
Not Touching That
After an entire season of failed weather models and the ongoing consequences of “the winter that wasn’t,” Day isn’t extending his extended forecast. He was even hesitant to look very far beyond the upcoming weekend.
“There is a cold front coming this weekend, mainly Saturday night and Sunday, that’s likely to cool us off quite a bit,” he said. “There's probably going to be precipitation with it, but at this point in time, I'm not going to touch anything beyond that with a 10-foot pole.”
Some weather outlets have called for a snowstorm along the Wyoming-Montana state line this weekend, like the one that hit southeast Wyoming last week. Some models show as much as 10 inches of snow in Johnson County over the weekend.
Day said it’s “not good practice” to make confident claims this far out, let alone in moody May.
“I’m not going to start throwing out inches that far in advance,” he said.
Day advised people to trust local, short-range forecasts and the trends they’re seeing in real-time.
“Trend is your friend,” he said. “I've got some models that definitely show colder, wet weather statewide on Sunday, and some models that don't show that at all. I would say the trend is that the latter half of the weekend and early next week is colder.
"There's possibly some precipitation with that colder weather coming, but that's as far as I'm going to go.”
Dziewaltowski shared a similar caution while reassuring Wyomingites that nothing’s stuck in place. We’ll be riding the roller coaster for the foreseeable future.
“There’s no indication that we're locked into hot, dry weather,” he said. “Conditions are more volatile. We’re looking at more up-and-down swings over the next two weeks, and that’s normal for these transition seasons.”
Andrew Rossi can be reached at arossi@cowboystatedaily.com.
