THIS AVALANCHE ADVISORY EXPIRED ON February 19, 2020 @ 5:38 am
Avalanche Advisory published on February 18, 2020 @ 5:38 am
Issued by Ben Bernall - Kootenai National Forest

Kootenai

bottom line

Fresh snow from the weekend and westerly winds this past week have created wind slabs on steep, leeward terrain above treeline. Wind loaded slopes below ridgelines and cornices are where you will find trouble if you go looking for it. The new snow is also resting on potentially weak or smooth surfaces out there that have the potential to slide in terrain steeper than 35°. Details below!!

How to read the advisory

Fresh snow from the weekend and westerly winds this past week have created wind slabs on steep, leeward terrain above treeline. Wind loaded slopes below ridgelines and cornices are where you will find trouble if you go looking for it. The new snow is also resting on potentially weak or smooth surfaces out there that have the potential to slide in terrain steeper than 35°. Details below!!

2. Moderate

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Above Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

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Near Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Wind Slab
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This past weekend the area recieved a couple shots of fresh snow. This accompanied with more steady winds has continued to build cornices and load more fresh snow into leeward terrain at upper elevations. I would avoid steep terrain just below ridgelines for a couple of days. If it has a big cornice above it, avoid it. Other signs to pay attention to are cracking snow and increases in density in the snow surface. Most of the new snow is light and soft, in areas where it has been affected by the wind the snow will feel firm and dense, a sure sign you are standing on a wind slab.



NorthWest Peak in Purcell Range. Easterly aspect.

Avalanche Problem 2: Persistent Slab
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This weekends snow storms came in and left us with some fresh snow that is light and mostly low density. It is just cohesive enough to form soft slabs. In the Cabinets the new snow is resting on some firm, wind hammered surfaces and you can expect the new snow to possibly release in the form of surface slough or small slabs in steep terrain. In the Purcells we have a very different scenario. Cold temperatures have created a couple layers of weak sugary snow (facets) prior to our last snowfall. The top 8-10" of snow is worth paying attention to right now. If the upper layer of snow feels dense and "slabby" it may be cohesive enough to cause you harm; otherwise, you are likely to see the new snow slide in the form of surface sloughing. These facets are weak layers to keep an eye on, particularly if we recieve more snowfall next weekend.

advisory discussion

On February 17th we travelled into the North West Peaks Scenic Area to check out the Purcell snowpack. The Purcells always seem to have something a little different going on when compared to the East and West Cabinets. Right now the big difference is in the February 1st rain crust that is found area wide. In the Cabinets this crust is 1-3" thick, in the Purcells it is much thinner and has far more facet development going on underneath it. There are also well developed facets under the fresh snow we received last weekend as a result of the colder temperatures that the Purcells like to harbor. The Cabinets are also stacking up twice as much snow as the Purcell Range, if you are looking for deep and soft, then the West Cabinets are your spot right now. The riding is great up North, but you won't find the depth that the West Cabinets are sitting on.

The thing they all have in common though right now is the prevalent wind loading issue that has been a frequent problem lately. Looking out into the future, the predicted weather shows some pretty calm conditions in store for us this week. It appears we may see the sun, less wind and no snow in the upcoming days. With these cold and calm conditions we are also likely to grow some good surface hoar out there that may line up to be the next problem, time will tell! Check out the video below to see an un-edited look at the snowpack! Never mind the awkward pauses and stuttering!

 

 

Weather and CURRENT CONDITIONS
weather summary 
Backcountry Forecast from NWS Missoula issued:
450 AM MST Tue Feb 18 2020

DISCUSSION: 

Northwest Montana: A weak wave moving south out of Canada will enhance
light snowfall today, primarily through the Whitefish/Swan Ranges
and Glacier National Park. Accumulations will be variable due to
the showery nature, though favored high terrain areas could see 3
to 6 inches. An arctic airmass is wedged up against the east side
of the Divide this morning, and while colder air is evident at 
Marias Pass and is slowly seeping through the Highway 2 corridor, 
it is not anticipated to push as far west as Essex. The colder air
quickly slides further east this afternoon with showers decreasing
by late afternoon. High pressure will promote mostly clear and 
calm nights Wednesday and Thursday with warming temperatures in 
the terrain and valley inversions.
Kootenai:
--------------------------- 5000-7000 FT ----------------------------
                      Today        Tonight      Wed      
Cloud Cover           30%          20%          10%      
Hi/Lo Temps           20 to 28     4 to 10      23 to 30 
Winds(mph)            NW  9        N  6         SE  7    
Precip Chc            0            0            0        
Precip Type           none         none         none     
Liquid Amt            0.00         0.00         0.00     
Snow Ratio(SLR)       0            0            0        
Snow Amt(in)          0            0            0        
Snow Level            0            0            0
Disclaimer

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.