This latest story from the Weather Company highlights potential for a major snow in Montana, with lessor amounts into Wyoming including Star Valley
Weekend Blizzard May Be a September Benchmark Snowstorm in Montana, Dumping Over a Foot of Snow
Published: September 25, 2019
A late September blizzard is increasingly possible this weekend in parts of the northern Rockies, and some lower elevations of Montana, Wyoming and the western Dakotas could see their first snow of the season just days after the official arrival of fall.
The jet stream will take a sharp, southward plunge from western Canada into the Northwest late this week. That will send temperatures crashing well below average for this time of year.
Snow will become more widespread later Friday and continue through the weekend in the northern Rockies of Idaho, Montana and Wyoming.
A second round of snow may blanket the northern Rockies and parts of the northern High Plains from Monday into Tuesday or even next Wednesday.
Some lower-elevation cities will see their first measurable snow of the season, including Great Falls and Helena, Montana. That’s not too unusual since the average date of the first snowfall is Oct. 2 in Great Falls and Oct. 12 in Helena. The higher elevations of the northern Rockies have already seen snow earlier in September.
But this round of snow will be much heavier and more widespread and could impact travel through passes in the region.
The National Weather Service has issued a winter storm watch for parts of northwestern and north-central Montana from Friday evening through Sunday afternoon.
The strong wording in this watch from the NWS office in Great Falls, Montana, Wednesday morning was eye-opening.
“This early-season winter storm and/or blizzard has the potential to set a new benchmark for snow accumulations, cold temperatures and resulting impacts for parts of the northern Rockies and the Rocky Mountain Front,” NWS-Great Falls wrote.
How Much Snow?
The heaviest snow totals are expected in parts of northern and central Montana, where over a foot of snow is probable. Some of these areas may see multiple feet of snow. Some heavy totals are also expected in other parts of central and western Montana and higher elevations of northern and western Wyoming.
Some lower elevations could also see significant accumulations of wet snow, particularly on grassy areas in the northern High Plains of eastern Montana, northeastern Wyoming and perhaps the western Dakotas early next week.
Early fall snowstorms are often destructive.
The combination of heavy, wet snow and strong winds this weekend may lead to widespread tree damage, power outages and blizzard conditions in parts of Montana, according to the NWS.
Travel in parts of central and western Montana, possibly into northwestern Wyoming, is likely to become dangerous, if not impossible, especially over mountain passes and in open areas where blizzard conditions could quickly reduce visibility.
NWS-Great Falls compared the potential of this snowstorm to another storm in late September 1934, which produced over a foot of heavy, wet snow in both Cut Bank and Great Falls, Montana, and over 6 inches of snow in Helena, Montana.
More recently, an early October 2017 snowstorm dumped over a foot of snow, leading to widespread power outages and downed trees in northern Montana, including the city of Havre.
High temperatures are likely to be 10 to 35 degrees below late September averages this weekend from Northern California and northern Nevada to Montana, Idaho and Wyoming. Daytime temperatures holding in the 30s, 40s or 50s could set daily record-cold highs Saturday through Tuesday in parts of the northern Great Basin and northern Rockies.
Temperatures will plunge below freezing at night in parts of the northern Rockies. Lows will bottom out into the 20s – or perhaps a few upper teens – in the northern Rockies. Some daily record lows are possible in the Northwest early next week.
This taste of wintry weather during fall’s first weekend will be in stark contrast to the summerlike heat ongoing at the same time in portions of the East.
The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.