THIS SNOWPACK SUMMARY EXPIRED ON March 1, 2017 @ 11:09 am
Snowpack Summary published on February 28, 2017 @ 6:09 pm
Issued by Ben Bernall - Kootenai National Forest
Avalanche Character 1: Wind Slab
Wind Slab avalanches release naturally during wind events and can be triggered for up to a week after a wind event. They form in lee and cross-loaded terrain features. Avoid them by sticking to wind sheltered or wind scoured areas.

The Kootenai has seen multiple storms roll through the area leaving behind abundant amounts of light density snow.  At upper elevations this new snow is being transported and compacted by strong, erratic winds.

Bottom Line: Skiers and snowmobilers will likely find isolated wind slabs at elevations above 5,500' on any aspect.  These slabs will pose the most danger just below ridgelines and in cross-loaded gullies in steep, open terrain.  Thickness of these wind slabs will be 1-2' in depth and have the potential to increase in size and reactivity with the predicted weather.   Approach these terrain features with caution as there will be a high likelihood of human triggered avalanches in these areas.

Avalanche Character 2: Loose Dry
Loose Dry avalanches exist throughout the terrain, release at or below the trigger point, and can run in densely-treed areas. Avoid very steep slopes and terrain traps such as cliffs, gullies, or tree wells.

In areas where the snow is unaffected by wind it is loose, dry and deep.  Its the snow that is worth skipping work to go play in.  It is also the kind of snow that may entrain you in very steep terrain.

Bottom Line: Use caution in steep terrain where loose snow and sloughing may overtake you and increase consequences of losing control.

Snowpack Discussion

Check out the forecast for the Idaho Panhandle below!

http://www.idahopanhandleavalanche.org/current-advisory.html

recent observations

Today we travelled into the Upper Bear Creek drainage of the Eastern Cabinet Range.  The snow was deep and getting deeper as the day went on.  We climbed up the hill breaking trail through knee deep, light density powder.  As we climbed over 5,500' and approached the ridgeline we began to experience strong winds that seemed to switch direction constantly.  The loading and slab development was at its worst on the southerly aspects but we experienced some degree of wind effect on the north side as well.  We performed stability tests on both the north and south aspects and noted failures on a melt-freeze crust 1.5-2'(locaton dependent) below the surface.  These failures did not show a tendency to propagate in extended column tests as a result of the low density snow having not formed a cohesive slab in areas sheltered from the wind.  Though pit tests made the snowpack appear relatively safe in sheltered areas it is likely to change for the worse as one moves into more exposed, high elevation terrain.



Nate Stephens displaying the depth of new snow while braving the ridgeline winds.

 

The thin melt freeze crust 1.5 feet below the snow surface resting on weak, sugary snow (facets).                

weather

Backcountry Forecast from NWS Missoula issued:

220 PM MST Tue Feb 28 2017



DISCUSSION: The snow will break up into snow showers early this

morning then decrease until this afternoon when daytime heating

makes it unstable again. Tonight another plume of moisture on

unstable northwest flow brings more snow showers to the region.

Strong northwest flow will bring numerous moderate light density

mountain snow showers on Wednesday. Graupel/snow showers are

possible in the valleys during the day. Ridgetop winds will range

between 40 and 60 mph. Light snow showers Thursday across

northwest Montana before a fairly wet system with higher snow

levels moves in by Friday night.

Kootenai:



--------------------------- 5000-7000 FT ----------------------------

                                 Tonight                     Wed              Wed Night    Thu     

Cloud Cover            85%                95%              95%               95%     

Hi/Lo Temps           10 to 16          26 to 32        19 to 25         29 to 34

Winds(mph)            SW 18G45     W 27G53      W 18G37      SW 15G33

Precip Chc               100                 100               80                  90      

Precip Type              snow              sno/shr         sno/shr           sno/shr 

Snow Amt(in)          2-5                 4-8                2-5                 2-5     

Snow Level             500                 1500             2500               2500  

Disclaimer

This advisory applies only to backcountry areas outside established ski area boundaries. This advisory describes general avalanche conditions and local variations always occur. This advisory expires midnight on the posted day unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.