FAC Avalanche Advisory for 28 Dec. 2012


Issue Date

8:00 am – Friday December 28

Valid Until

Midnight – Friday December 28

Next Update

Saturday December 29


Because of the general nature of this advisory, each party will need to make their own time- and site-specific avalanche hazard evaluations. This advisory best describes conditions at the time of it’s issuance. As time passes avalanche and snow conditions may change, sometimes quite rapidly. Elevation and geographic distinctions used are approximate and transition zones between hazards exist. This advisory does not apply to developed ski areas.



For the Flathead/GNP and the Kootenai all terrain is rated as:



Cloud ceiling was evident from valley locations early this morning.  Light snow fell throughout the day with insignificant accumulations.  Winds were calm in Northern Swan, although not so calm in Glacier NP on the ridge above John F Stevens Canyon where winds were moderate with strong gusts. Mountain temperatures were in the low 20’s to upper teens.

The snowpack is mostly stable and is topped with generally soft snow in the surface 30 to 40 cms.  Stress tests are not producing concerning results at this time.  Instability associated with the surface 20 to 30 cms is moderating but certainly could be found to be tender on northerly aspects as temperatures stay on the cool side.

The Purcells in the Kootenai and the Northern Swan in the Flathead had two observations that were leaning towards a stabilizing effect within our snow pack, not so in John F Stevens Canyon.  At treeline and above, west winds were transporting available snow from windward westerly aspects to leeward easterly aspects.  This transported snow was being deposited as windslab on previously scoured east facing aspects and was very sensitive to triggering.


Weak weather disturbances will move through the region through Sunday.  Light snow is expected with very little accumulations.  Next week is forecasted to be mainly dry and warmer under a building ridge.   Settlement within the snow pack could be expected to occur in the coming week with the intro of this building ridge.   

 The general avalanche hazard is expected to be MODERATE across our region.  As demonstrated on Christmas Day MODERATE means it is possible to trigger an avalanche and each party needs to make site specific assessments.  As well, wind loaded convex rolls and ridges will still be a concern where wind transport is occuring, especially on either side of the Middle Fork Corridor.

Please see the current NWS (backcountry weather forecast).



 At this time the avalanche hazard is not expected to change significantly.  Temperatures should stay on the cool side through the weekend.  We will just have to wait and see how the predicted weather change will affect our snow pack beginning early next week.



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