THIS AVALANCHE ADVISORY EXPIRED ON February 27, 2019 @ 4:35 am
Avalanche Advisory published on February 26, 2019 @ 4:35 am
Issued by Ben Bernall - Kootenai National Forest

Kootenai

bottom line

Strong northeasterly winds have created windslabs in atypical locations and they will continue to build through the day Tuesday. Use caution in steep terrain below ridgelines, steep and convex rolls and cross-loaded chutes. Better snow, less wind and safer conditions can be found in the sheltered protection of the timber right now. 

How to read the advisory

Strong northeasterly winds have created windslabs in atypical locations and they will continue to build through the day Tuesday. Use caution in steep terrain below ridgelines, steep and convex rolls and cross-loaded chutes. Better snow, less wind and safer conditions can be found in the sheltered protection of the timber right now. 

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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Yet another cold front has entered the area and it has brought its cold northeast winds along the way. Loose snow that fell last Friday night is being transported onto westerly aspects and packed into pillows of wind slab just below ridgelines, steep rolls and in cross-loaded chutes where the wind is blowing across the slope. With the cold front and its easterly wind component the slabs will be forming on atypical locations and in some areas may be resting on top of last weeks hard-slab surface or sun crust on southerly faces. Use caution in the above mentioned terrain features and watch for the obvious clues such as shooting cracks in dense pillows of snow pictured below.



Photos taken on 2/25 in Keeler Rattle area.

Avalanche Problem 2: Persistent Slab
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The "Persistent Slab Problem" will continue to persist with the cold temperatures that gripped the area this past week. The likely problem areas will be steep ribs or steep ridgeline features where the thinner snowpack is more susceptible to faceting that is driven by the cold temperatures. These thinner areas in the snowpack are where you are also likely to "trigger" a persistent weak layer. Use caution in the above mentioned features and be alert to this potential when riding in steep and rugged terrain of the Purcells (NW Peak/Rock Candy area).

advisory discussion

So, it's cold and windy. From and avalanche standpoint I would say that wind slabs in steep, westerly facing terrain are your biggest concern. But, right now it is worth thinking about the fact that even a minor accident will have the potential to rapidly decline into a bad situation with the cold temps and wind chill factor. Bear this in mind when making your decisions on where to ride, who to ride with and any contingency items that you may want to have in your pack when Murphys' Law slaps you in the face.

As far as observations go: Our snowpack is getting thicker and generally we are under some pretty stable conditions area wide. The continuous winds last week created some very firm slabs and there are also some thin sun crusts on solar aspects that may provide a slippery bed surface. These surfaces will be the locations where the new wind-slabs will be most reactive and easily triggered. The Persistent weak layers are out there still but they will be stubborn and difficult to trigger. This can be bad thing as it often allows riders to get away with riding in terrain that may be suspect and lure them into a sense of false security. I would continue to approach steep terrain with caution in the Purcell Range, especially if it appears to have thin coverage. 

Weather and CURRENT CONDITIONS
weather summary
Backcountry Forecast from NWS Missoula issued:
500 AM MST Tue Feb 26 2019

DISCUSSION: Snow will taper off today across much of the Northern
Rockies, however up to a few inches accumulation remains possible
for the Flint Creek and Anaconda Ranges of southwest Montana. East
and northeast winds will continue to blow snow around, however
gusts will diminish throughout the day. Temperatures will remain
very cold for this time of year, particularly for western Montana
ranges.

The next snow producing system will move over the Northern 
Rockies on Wednesday, with up to several inches new snow 
accumulation. Similar to the recent storm, snow to liquid ratios 
will remain near 20:1. Temperatures across the region will warm 
during the Wednesday snow event, particularly over the Clearwater 
Mountains.


Kootenai:
--------------------------- 5000-7000 FT ----------------------------
                      Today        Tonight      Wed      
Cloud Cover           30%          15%          75%      
Hi/Lo Temps           7 to 15      -4 to 3      17 to 26 
Winds(mph)            NE 14G28     NE 11G26     NE 12G26 
Precip Chc            0            0            60       
Precip Type           snow         none         snow     
Liquid Amt            0.00         0.00         0.04     
Snow Ratio(SLR)       20:1         0            19:1     
Snow Amt(in)          0            0            0-2      
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.