THIS AVALANCHE ADVISORY EXPIRED ON February 8, 2020 @ 5:27 am
Avalanche Advisory published on February 7, 2020 @ 5:27 am
Issued by Ben Bernall - Kootenai National Forest

Kootenai

bottom line

For Friday anticipate the possibility to trigger small pockets of dense wind slabs above 6,000' in elevation where northwest winds have deposited loose surface snow onto southerly aspects. By Saturday morning the avalanche danger will likely rise with a predicted storm expected to bring 8-12 inches of new snow to the mountains and strong southwest winds. New snow may bond poorly with the existing surface in many locations.

How to read the advisory

For Friday anticipate the possibility to trigger small pockets of dense wind slabs above 6,000' in elevation where northwest winds have deposited loose surface snow onto southerly aspects. By Saturday morning the avalanche danger will likely rise with a predicted storm expected to bring 8-12 inches of new snow to the mountains and strong southwest winds. New snow may bond poorly with the existing surface in many locations.

2. Moderate

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

1. Low

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Near Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

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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On February 6th we observed strong northwest winds through out the day. Small amounts of loose surface snow were being easily transported off the ridgelines and deposited into southerly facing aspects and chutes. These pockets are likely to be stiff and resistant to triggering but are likely to be the biggest threat on Friday. Friday night is expected to bring more snowfall and a wind switch, back to the general southwestely flow. On Saturday the new snow will most likely be developing pockets of wind slab on the northeasterly sides of the mountain. WIth these aspects being scoured down to the thick rain crust, the new snow will likely slide easily this weekend.

Avalanche Problem 2: Storm Slab
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This is likely a problem for Saturday! We have yet to see much snow in the mountains out of the northwesterly flow that has been present the past few days. The snow seems to be slipping to the south of our area. The current forecast is predicting 8-12" in the mountains at this time above 3,000' by Saturday morning. If this actually shakes out we will see the avalanche danger rise considerably by Saturday morning. Again, with our current surface out there the new snow will have a tough time bonding this weekend. Be very alert to this upcoming possibility if you are heading into the mountains on Saturday!

advisory discussion

On Thursday we rolled into the East Cabinets to once again practice the art of skiing uphill on hard, crusty snow. The mountains have been dusted with 2-3" of new snow that is covering last weekends thick and hearty rain crust layer. In open areas and ridgelines this thin layer of new snow was getting blown around by strong northwest winds and deposited onto steep leeward terrain and shallow depressions forming thin but dense wind slab layers. Taking a closer look at the snowpack brings up two primary concerns right now and they are both close to the surface. The first one to be aware of is a sandwich of lighter snow and graupel between last weekends thick rain crust and the 2-3 inches of new snow on the surface that is fairly dense and cohesive. It was showing more strength than I expected yesterday but it has the potential to be the weak point if and when new snow falls. On Monday we were also seeing some scattered surface hoar growing on the crust that is likely lurking out there in sheltered openings. A fresh foot of snow may be a problem on Saturday if it comes in on the warm side with a little bit of wind behind it!

The other concern that catches my eye is the areas where the winds have scoured the new snow down to the firm and icy rain crust. Upper elevations that have been stripped bare will slide easily on Satuday if the predicted snow fall does indeed arrive. How hazardous this new snow will be is dependent on how it comes in. If it falls on the warm side with low snow-to-liquid ratio we will have a storm slab problem that may be easily triggered by a human on machine or skis. I'm crossing my fingers for cold and light powder falling calming from the sky; but, that's just me trying to be an optimist!

The "take-home" message is that much of the avalanche hazard right now hinges on the weather Friday night into Saturday morning. Be sure to check out the Snotel sites before you go out Saturday morning and play a cautious game to start out the day until you have thouroughly assessed the conditions out there.

 

Weather and CURRENT CONDITIONS
weather summary 
Backcountry Forecast from NWS Missoula issued:
430 AM MST Fri Feb 7 2020

DISCUSSION: 

Northwest Montana: Light snow accumulations (under 6 inches) are
anticipated through this morning mainly in the Glacier Park, 
Great Bear Wilderness areas. Another snow event is anticipated 
for this evening through Saturday, with accumulations more in the
8 to 16 inch range. Southwest winds gusting as high as 40 mph at 
the ridges on Saturday afternoon will cause blowing snow and 
reduce visibility. Snow levels look fairly stable during the 
Saturday storm, however temperatures at high elevations will cool 
around 5 degrees from Saturday to Sunday. The next snow event is 
projected around the middle of next week, however models have 
mostly abandoned the notion of a much cooler airmass than those of
late.
Kootenai:
--------------------------- 5000-7000 FT ----------------------------
                      Today        Tonight      Sat      
Cloud Cover           65%          95%          100%     
Hi/Lo Temps           27 to 34     21 to 27     25 to 32 
Winds(mph)            W  9G23      SW 17G33     W 19G37  
Precip Chc            0            100          90       
Precip Type           snow         snow         snow     
Liquid Amt            0.00         0.47         0.14     
Snow Ratio(SLR)       18:1         16:1         20:1     
Snow Amt(in)          0            6-12         2-4      
Snow Level            2000         3000         2000
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.