Big Winter Storm To Hit Western North America This Weekend

Total moisture for the west through October 1st (next Tuesday). Weatherbell image.

You can pretty much flip the switch from Summer/Fall-like temps this week to a more December-like pattern by late this weekend. Unseasonably cold air will impact most of the Rockies, Pacific Northwest and Sierra by Friday and turn even colder early next week. You might be able to ride your favorite mountain bike trail Thursday or Friday followed by skinning some moderate POW by early next week in a few isolated areas of the west. Valley snow is likely, especially in north/central Montana where precipitation may be heavy by late this weekend. Bob Nester from the National Weather Service in Missoula Montana summed it up with, “There is a cut off low that is going to hover over the northern Rockies for several days” “That low is set to stall, with no upper winds to push it along until the Jet Stream eventually moves it out sometime next week”. He stated that it's more often a pattern seen in the spring versus the fall.

RELATED: Jackson Hole and Big Sky See More Early Snow

Weather models are finicky, opt to changes, and in some cases can make full reversals five to seven days out. Confidence however is high that a significant trough of low pressure will drop from the Pacific Northwest/Canada into the northern Rockies by late this week. Initially the highest amounts of snowfall are likely over Alberta (Sunshine Village, Lake Louise) with slightly lower amounts over interior BC early this weekend. Whistler and the Cascades of WA and OR may also see its first snow of the season albeit lighter than its counterparts further inland. Areas inland in Canada, especially Alberta may see up to 10-15 inches of snow by Sunday afternoon!

Confidence is also high that temperatures late this week into early next will plummet bringing a more December like pattern than September.

Temps plummet through the weekend and into early next week over much of the west. Image: 10K feet temps in Celcius significantly below normal- Image- Tuesday October 1st. Weatherbell image.

In northern Montana weather models are consistent with mountain top temps at 10,000 feet to plunge to the low teens with valley locations in the 20’s. Along the Canadian border and further north expect temps to drop into the single digits at summits of many ski areas.

“We might see upwards of 2 feet of snow in Glacier National Park by late Sunday” says Bob Nester from the National Weather Service in Missoula. Bob also went on to say “We are going to get close to breaking the record low temp of 20 degrees for Missoula on Monday”

So who gets the deepest dump according to Powderchaser Steve? My confidence is highest for double digits in many areas of inland Canada, especially Alberta. Montana stands good odds of double digits near Glacier National Park extending south over much of the central portions of the State. This might include Big Sky and Bridger Bowl as wildcards but it's a bit early to instill high confidence on exactly who sees the most snow. Great Divide Ski area near Helena might be a better bet.

In Wyoming, the Tetons will begin to see light or moderate snow during the weekend. Higher amounts will be falling east of the Tetons into the Wind River range and central Wyoming along the Divide. Regardless, some moderate snow is likely for both Jackson Hole Mountain Resort and Grand Targhee who both saw 7-8 inches at upper elevations last week. This weekend might be deeper but it's still 5-7 days out.

Light to moderate snow at the base of Grand Targhee Ski area from September 20th. Powderchasers.com photo.

The Wasatch may also bring some surprises especially on Sunday or Monday with moderate or heavier snow falling. Even the Sierra is likely to see a taste of winter this weekend albeit it’s likely amounts will be light.

Colorado is on tap for the leftovers especially in the northern mountains early next week. It's really too early to speculate. Currently the models are struggling with amounts. They have flip flopped in the past few days.

Total snowfall from the GFS (Courtesy of WeatherBell) through next Tuesday October 1st. Amounts in blue are approaching 2 feet with current models showing north central Montana in the bullseye.

Bottom Line: Cooler temps impact the West by Thursday with some light snow especially northern Montana and Canada. I am confident on much colder temps impact these areas during the weekend as snow ramps up which may linger through early next week. Heavy snow is likely in many areas of BC, Alberta, and north/central Montana. I am confident on big snow totals in some locations, just not confident on exactly where since we are 5-7 days out. Look for some teases in the Sierra and Cascades. Moderate snow is likely for areas of northern Utah, south-central Idaho, southern Montana and the Tetons in Wyoming. Colorado is a wildcard at this point. This of course could all change by the time the weekend rolls around, but that's what makes weather exciting.

-Powderchaser Steve 

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