THIS AVALANCHE ADVISORY EXPIRED ON February 6, 2019 @ 5:13 am
Avalanche Advisory published on February 5, 2019 @ 5:13 am
Issued by Ben Bernall - Kootenai National Forest

Kootenai

bottom line

We continue to see reactive surface hoar buried 2' below the surface on sheltered (north and east) aspects between 5,000' to 6,000'. These slabs will be difficult to trigger but will cause large avalanches if triggered. In steep terrain (over 40°) loose snow will slough easily and may be dangerous in areas where cliffs or trees may cause bodily harm. Stay on your feet and make sure you can manage the "loose-dry" problem before committing to steep terrain.

How to read the advisory

We continue to see reactive surface hoar buried 2' below the surface on sheltered (north and east) aspects between 5,000' to 6,000'. These slabs will be difficult to trigger but will cause large avalanches if triggered. In steep terrain (over 40°) loose snow will slough easily and may be dangerous in areas where cliffs or trees may cause bodily harm. Stay on your feet and make sure you can manage the "loose-dry" problem before committing to steep terrain.

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: Persistent Slab
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The magnum sized surface hoar that we buried back in mid January is still there. At the lower elevations it has ceased to be a concern in most locations. Yesterday we began to feel collapsing and cracking in that narrow band of elevation between 5,500' and 6,000'. Multiple extended column tests revealed clean and snappy shears with moderate to hard force at these elevations. It will likely be difficult to trigger; but, there was 22" of cohesive slab on top of it and it will create a destructive slide if you find that sweet spot.  Short video of pit here⇒ https://youtu.be/Ve__9WWfYys



Mid January surface hoar layer 2cm thick. On NE aspect @ 5,800'.

Avalanche Problem 2: Loose Dry
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The cold front that entered the area left us with 8-10" of very loose, dry and cold snow on the surface at treeline and above. In most areas at these elevations it is poorly bonded to the old snow surface and was sloughing easily in terrain steeper than 40°. The big thing here is to pay attention when going into steep terrain and plan ahead, a quick ski cut will likely clean this loose snow out pretty quick. There is enough surface snow to entrain a rider and drag them over a cliff band or trees in steep terrain. Don't be that guy!



Loose dry sloughing in steep terrain. East Cabinets @ 6,000' and above.

advisory discussion

Yesterday we travelled into the East Cabinets expecting to find nasty wind slabs and found absolutely zero sign of wind. This baffled me as a cold front generally will hammer the mountains with northeasterly winds. I think it is highly possible that one may find that problem developing in isolated areas across some of the other ranges such as the Purcells or West Cabinets and I think it would be wise to stay alert for that potential as you are out there riding in higher terrain.

Here's what I did see! Warm temperatures from last Friday and Saturday did a good job of breaking down our latest batch of surface hoar before more snow came into the area and this will bode well for future stability. There was a firm supportive crust under foot up to about 5,000' with 6" of new snow on top of it. Between 5-6,000" on Northeasterly aspects is where we are still finding the layer of buried surface hoar from mid January. Experienced some collapsing and "whumpfing" at this elevation and pit results revealed it is indeed still there and harboring the potential to wreck your day if you trigger it. Pay attention to these signs and this "mid-elevation" band of instability, it loves to breed complacency and surprise unsuspecting riders. Above this elevation the new snow fell on pretty firm surfaces, it is still very light and loose and we found no signs of slab development in the new snow yet. As mentioned it is causing more of a "loose-dry" sloughing problem in steep terrain. We have a cold week in front of us and I would continue to watch this new snow at upper elevations for changes in density and slab development as a cold front will typically form wind slabs on south and westerly aspects. It is also likely that we will start to see some faceting below the upper crust layers as the cold air begins to drive moisture up within the snowpack. Tomorrow problems! For a quick video summary click here⇒ https://youtu.be/1B8BceER00A

Weather and CURRENT CONDITIONS
weather summary
Backcountry Forecast from NWS Missoula issued:
420 AM MST Tue Feb 5 2019

DISCUSSION: Scattered showers will continue to move through
northwest Montana this morning. These showers will be capable of
producing an inch of new snow in the higher terrain. A surface low
pressure will move across southern Idaho later today producing
wrap-around precipitation across Idaho county into southwest 
Montana. This system will be able to produce 2 to 8 inches of 
snow, particularly in the southern Clearwater, Bitterroot/Sapphire
mountains and Anaconda range. Northerly flow aloft will remain 
over the region on Wednesday causing scattered light showers. 

Kootenai:
--------------------------- 5000-7000 FT ----------------------------
                      Today        Tonight      Wed      
Cloud Cover           75%          70%          30%      
Hi/Lo Temps           9 to 15      -4 to 4      9 to 15  
Winds(mph)            NE  9G23     NE  9G22     NE  9G22 
Precip Chc            30           0            0        
Precip Type           snow         snow         none     
Liquid Amt            0.01         0.00         0.00     
Snow Ratio(SLR)       20:1         20:1         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.