The European model animation gives the straight-forward, or big picture on our upcoming weather pattern for Tuesday through Thursday night. Follow the trough of low-pressure (in purple/blue) as it ventures from the eastern Pacific through inland BC and eventually into the Northern Rockies. Not huge, but some moderate accumulations will be likely, especially west of the Divide.  

West of the Continental Divide:
 
Transient high-pressure on Tuesday is being flattened as a Pacific low-pressure trough is making its way through inland BC. This trough along with an associated cold front will trigger an increase in gusty SW winds with light snowfall developing by mid-afternoon along the Idaho border at Lookout Pass, and late afternoon up north at Whitefish. Snowfall engulfs the entire region Tuesday night and looks to last in various intensities through mid-morning on Wednesday. Snow levels will vary between 4000’ at areas along and south of I-90, and 3500’ for resorts/areas north of I-90. 

Short-term forecast models are tracking the heaviest snowfall along the Idaho border where Lookout Pass is best positioned for 5 – 10” through Wednesday morning. Lost Trail and Turner could see 4 – 7”, with 3 – 6” at Whitefish. Snowbowl, Blacktail, and Disco around 1 – 3”. Slightly colder on Wednesday with upper mountain highs in the low 20’s. Moderate and gusty W/SW winds continue through Wednesday morning, laying down a bit in the afternoon. 

High-pressure will fill in behind the departing system for Thursday and Friday delivering a daily forecast of sun and clouds across the region. Mountain temps will generally be right around seasonal averages on both days, with upper-mountain (6K’ to 6500’) high temps ranging from 23 -26F on Thursday, to 26 – 30F on Friday. Light SW winds both days.       

East of the Continental Divide:

Below: A gloriously sunny morning frames Lone Mountain at Big Sky.

 

Decreasing W/SW winds along with a weakening high-pressure ridge will bring a generally sunny day across the region for Tuesday. Mild upper-mountain (8000’) high temps on Tuesday will range from 25F to 29F with W/SW wind gusts to 20 mph on the ridgetops.  

A Pacific cold-front will move southeastward over the Continental Divide early Wednesday morning. Most of the moisture will be squeezed out of this low as it moves over the Divide but locations across SW Montana (Big Sky, Bridger Bowl, Maverick) and the North Central mountains (Showdown) will see periods of light snow, with 2 – 4” possible by days end on Wednesday. Teton Pass and Great Divide could also see 1 – 2” with only a slight chance of an inch at Red Lodge. It will also be windy across the alpine and upper-mountain locations across the region Wednesday creating drifting snow. NW winds in the moderate category with gusts 30 – 40 mph. Much colder on Wednesday with highs in the low to middle teens at 8000’ across the region. 

High-pressure amplifies on Thursday for a mostly sunny day with decreasing winds. Temps will be cool, but right around seasonal. High-pressure looks to weaken across the region on Friday bringing a mix of sun and clouds becoming mostly cloudy during the afternoon hours. Slight warming of mountain temperatures on Friday with upper-mountain highs 27 – 30F. Light SW winds becoming gusty (to 25 mph) during the afternoon.       

Below: The HRRR high resolution short term forecast map for estimated snowfall across Montana. This storm system will move in across NW Montana late Tuesday afternoon and spread southeast through the state. The storm weakens a bit as it moves over the Divide. Highest amounts look to build along the Idaho border west of the Divide. 

 

West and East of the Continental Divide: 

Still a few questions on this weekend’s forecast. What we know is a deep Pacific trough will move inland with a large low developing over California. The best scenario given is for this incoming low to split bringing a much weaker low north into Idaho and the Northern Rockies Saturday into Sunday. The other scenario dissolves the split off low before it enters the Northern Rockies bringing a benign pattern of mainly cloudy skies with some sunny spells. Even if the weaker break off low moves into the Northern Rockies, snow amounts look to be light in the 1 – 3” range. Temps look to be seasonal through the weekend. 

Brief high-pressure is favored for Monday 2/13 before a better organized trough descends out of Canada on Monday night and looks to stick around into Wednesday morning across the Treasure State. All major weather models favor this deep, and fairly widespread trough to bring light to moderate measurable snowfall into the Northern Rockies. Stay tuned.   

Below: The reliable european model is in favor of developing a split in the  "California low" that will form in the Pacific trough this weekend. The weaker split low looks to possibly bring some light accumulations across the Northern Rockies this weekend. Better chances arrive Monday night through Wednesday as a more widespread trough moves southeastward out of Canada on a NW flow aloft. This one has potential.  

Thanks for tuning in. Next update Thursday 2/9.  

Powder Out – 

Bob