Likelihood ?CertainVery LikelyLikelyPossible
Size ?HistoricVery LargeLarge
We have a well developed layer of surface hoar out there that can be found on shady aspects above 5,000' in elevation. In the Purcells I was finding it about 8" below the surface, in the Cabinets it is likely to be 12" or more below the surface. It is gaining strength and is showing a low likelihood of propagating into an avalanche at this time; however, I wouldn't fully trust it just yet. Your likely spots to have trouble are very steep openings or convex rolls in the timber where the surface hoar was preserved prior to the last snowfall. There are also some weak sugar layers above and below the February 1st rain crust in the Purcell Range that I would continue to keep in mind, These layers are also trending towards a more stable state as the mild temperatures heal the snowpack.
The weather has been pretty mild lately, and that has been good for creating a stable snowpack. Overall things are looking pretty good out there. As I mentioned above we have a weak layer that is very pronounced under our last snowfall. If you dig down into the snow on shady aspects in the timber you will possibley find a thin grey streak in the upper snowpack. This layer of surface hoar was found yesterday at Flatiron and the flakes were 8mm tall, buried 7-8" below the surface. Stability tests show this layer is resistant to propagation and continuing to gain strength. Keep your hackles raised if you are riding in steep timber on northerly aspects until this layer is fully healed. In terrain that has been exposed to the wind and sun this surface hoar was likely destroyed before it had the chance to become a problem, if you are looking to play in steeper terrain then these south and westerly aspects will be safer choices right now.
Looking forward into the future we have some pretty significant winds and modest shots of snow predicted. Stay alert for the potential to build some thin windslabs in leeward terrain during the week if the predicted snow rolls in. Enjoy the springlike weather and keep shredding!
Backcountry Forecast from NWS Missoula issued: 340 AM MST Tue Mar 3 2020 DISCUSSION: Northwest Montana: Wind will remain the primary concern today and Wednesday. Westerly winds will increase this afternoon with gusts up to 40 mph expected. An upper level jet and surface cold front will further increase winds Wednesday. Westerly gusts in the neighborhood of 60 mph are possible across the Swan, Whitefish, and Flathead ranges. In addition to winds, several inches of snowfall are expected Wednesday. Convective snow showers will develop in the afternoon with graupel being possible.
Kootenai: --------------------------- 5000-7000 FT ---------------------------- Today Tonight Wed Cloud Cover 50% 90% 65% Hi/Lo Temps 30 to 39 21 to 29 26 to 34 Winds(mph) W 21G44 SW 20G40 W 29G49 Precip Chc 20 60 70 Precip Type snow snow snow Liquid Amt 0.03 0.19 0.08 Snow Ratio(SLR) 11:1 13:1 15:1 Snow Amt(in) 0-1 2-6 1-2 Snow Level 4000 4000 2000
Avalanche conditions change for better or worse continually. Backcountry travelers should be prepared to assess current conditions for themselves, plan their routes of travel accordingly, and never travel alone. Backcountry travelers can reduce their exposure to avalanche hazards by utilizing timbered trails and ridge routes and by avoiding open and exposed terrain with slope angles of 30 degrees or more. Backcountry travelers should carry the necessary avalanche rescue equipment such as a shovel, avalanche probe or probe ski poles, a rescue beacon and a well-equipped first aid kit. For a recorded version of the Avalanche Advisory call (208)765-7323.
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