Fall starts on Saturday. Colder air is moving into Montana on Thursday and will move south Friday bringing snow above 9,000 feet. This will be the first impactful storm of the season, however, it will be confined to the peaks.
Short Term Forecast
Good morning Powder Hounds! This will not be the epic storm I often write about, but instead our first good tease of decent moisture for the northern Rockies and the coldest temps of the season thus far. Fall starts officially on Saturday and temps in the northern Rockies will be approaching freezing even at the valley floor by Saturday morning (Wyoming, Montana). This event will at least get us thinking and dreaming powder for the upcoming season. Dreaming is almost as fun as the actual chase.
Cold air is moving in from Montana on Thursday morning. This will reach Wyoming late Thursday night or Friday morning. The models show the highest snow totals above 9K with some lighter amounts as low as 8K. Winds start out from the south and veer SE which is not a preferred direction for most ski areas. Upslope conditions will likely keep the highest amounts in northern Wyoming and southern Montana, especially closer to the Wyoming/Montana border. Driving north and east of the Tetons towards the Absaroka Range to Red Lodge might grab the highest totals at the peaks. Red Lodge Mountain normally does best with an NE wind direction where this event might skirt just west keeping totals lower. I would not be surprised to see 5-10 inches at some of the summits at the MT/WY border. Below 9,000 feet might see 1-3 inches. The Summit of Red Lodge is a wildcard.
Below: The American model showing some decent totals on the MT/WY border by Friday afternoon (Above 9K) The short-term high-resolution models show higher amounts further south into the Tetons but I am reluctant to buy into it just yet. With the southerly winds, it's possible that Big Sky also comes up with some measurable snow at the summit.
Models are not in great agreement with shifting winds from S, SE, to SW for the Montana Ski areas. It's likely some flakes are recorded at Showdown, and Discovery further east of Missoula. Big Sky often can do well with southerly winds so it's likely they will be reporting some snow on Friday morning.
For the Tetons, I have high confidence that on Friday as winds veer more SW (Versus S or SE) light snow will be falling at the upper elevations of the Tetons. The Wasatch will see higher moisture north of Salt Lake City toward the Idaho border. This will be a mostly rain event with the exception of the Cottonwoods which will likely grab 1-3 inches at the summits.
Below: Cold air is confined to Montana and Idaho on Thursday (-2C at 10K)
Below: On Friday morning this cold front has reached the Tetons and northern Utah when some snow is likely at the upper peaks. Friday night will see the coldest temps of the summer as Fall officially hits on Saturday (With clearing skies the 1st day of fall in the Jackson valley will be near freezing).
Below: University of Utah models based on the GFS showing snow for mid-mountain at Alta from late Thursday to early Friday (1-3 inches). This seems believable from looking at the models. Higher precipitation totals will fall in the northern Wasatch but temps might keep the snow levels above the summits.
Below: Average of multiple ensemble runs showing anywhere a mean average of around 2-3 inches for the summit of JHMR (Friday is the most favored wind direction).
The models for next week show another cold front is likely for the Pacific Northwest and BC. Low pressure is noted over the Cascades extending into most of BC and Alberta early or mid-next week. This system currently looks to traverse east and north into central Canada at some point mid or late next week. The models yesterday showed a different solution, digging south over the Rockies. It's likely that areas in Canada might be the highest beneficiaries of moisture but it is still too early to provide details.
Below: Colder temps are confined to the PNW, north Idaho/Montana- Canada with even a hint of a cool down for the northern Sierra. Map: 10K Feet in Celsius. (September 27 Wednesday).
Below: Next week will feature an approaching trough that impacts the PNW and areas of BC/Alberta. This will likely bring significant water totals to the Cascades cold temps initially Sunday, warming Monday, and cooling again by midweek. The temps will be much colder than average with 41-45 degrees at the bases and the possibility of seeing some flakes at some of the summits. BC and Alberta should score some white also.
Below: The first low moves north and east by late next week over central Canada (Yesterday, the models showed a different solution so confidence is low at this point). Another low is noted approaching the west coast late next week (September 29).
Thanks for following the chase forecast. I was in Alaska this summer photographing bears. If you want to check out some of my work and join me on the chase for adventure follow my Instagram feed below @powderchasersteve
Enjoy the rest of the summer, fall on Saturday, and see you on the slopes soon! It's always snowing somewhere!