Snow in the first week of September? It’s entirely possible, although some long-range forecasts can be misleading.
Chris Nunley, a meteorologist with FOX 13 Utah, shared a long-range forecast suggesting a cold front from the northern Pacific could descend on the Western U.S. during the first week of September.
The front could be strong enough to bring the first snowfall of the season to Wyoming’s mountains, especially in the western half of the state. The Wind River, Bighorn and Teton Ranges could be blanketed by Labor Day, and even the Snowy Range could get snowy.
Whether that will actually happen is far from certain.
It reminded Cowboy State Daily meteorologist Don Day of something he hasn’t and will never do when communicating weather to Wyomingites.
“I never post any graphics like that on social media,” he said. “People do it all the time, and I chide them for it. It drives me nuts and gets people all ramped up. I hate it.”
So, will it snow in Wyoming in September? Probably, Day said, but not immediately.
“There's a high probability of snowfall in the mountains in September, but I am not confident it's going to happen in that first week,” he said.
Snowy Septembers
Wyoming usually sees snow in September. The first blizzard of last winter’s season temporarily shut down the Beartooth Highway on Sept. 13.
Snow is expected at elevations above 10,000 feet by mid-September, but Day said there hasn’t been an “early high-country” snow in Wyoming for several years.
“I certainly think there’s a very good possibility for some snow in the mountains in September,” he said.
In that sense, the graphic shared by Nunley supports Day’s long-range forecast for the upcoming winter season.
Based on current weather patterns, historical data and long-range modeling, Day believes it’s going to be a longer, colder and snowier winter for Wyoming and the Rocky Mountain region.
“For this winter, overall, the whole state will be colder than last winter compared to the 30-year average,” he said. “There should be more snow and cold this winter than last on both sides of the Continental Divide. I’m sticking to that.”
So, does Day agree with Nunley and this two-week outlook? Not exactly, because it could be right for the wrong reasons.
The Computer Said So
Day’s concern with Nunley’s graphic is that it was produced by long-range weather modeling via computers.
While an extremely potent tool for weather monitoring and forecasting, Day said computer modeling isn’t the end-all, be-all and shouldn’t be treated as such.
“You see inconsistency with long-range modeling,” he said. “The data is a tool, but when you post a graphic from a model verbatim, the possibility that it’s going to change on the next model run is extremely high.”
Long-range modeling uses current weather patterns to anticipate future fronts and systems and how they’ll impact various regions. Day’s concern is how much can change from day to day, let alone over two weeks.
“Showing a graphic from that particular run shows that it may snow the first week of September,” he said. “Three or four other model runs later, or even the next one, it may not show that.
“So, do you post the next model run that doesn't show snow in September and say, ‘Oh, just kidding?’”
Day has cautioned against overreliance on long-range modeling for years, especially for Wyoming’s forecasts. In his experience, Wyoming’s weather is too erratic for confident forecasts two weeks out, let alone two months out.
Extreme Prejudice
Long-range forecasting puts Day in a difficult position. A modeling run that shows snow in the first week of September would support his long-range forecast for the upcoming winter, but he won’t let it.
“That graphic could end up being correct, but I don’t have the confidence level to tell people right now, at this point in time, that it's going to snow next week or that first week of September,” he said. “From what I’m seeing, I can’t say that.”
In Day’s opinion, graphics like the one Nunley shared should be taken with “extreme prejudice.”
The most reliable forecasts come from local sources, such as the National Weather Service offices in Riverton, Cheyenne and surrounding states that cover Wyoming.
With a three-day weekend ahead, many Wyomingites are wondering whether to pack a swimsuit or a snowsuit for their outdoor excursions. Based on what he’s seeing Tuesday, Day felt confident enough to say snow will stay away for Labor Day.
“I don't see it getting cold enough to snow in the mountains this Labor Day weekend,” he said. “Other than these afternoon showers and thunderstorms, especially on Saturday, I think it's going to be a decent three-day weekend weather-wise.”
Day isn’t ruling out snow during the first week of September, but two weeks is too far ahead for a forecast with strong confidence. Computers might say so, but he won’t.
“We kind of have to get the current pattern cleared out, see what evolves next as we go into sort of the next storm cycle, and see where things end up,” he said. “Could we get some high-country snowfall in early September? It's certainly a possibility, but by no means is it a foregone conclusion.”
Andrew Rossi can be reached at arossi@cowboystatedaily.com.
