I hope this finds Everyone enjoying these sunny days somewhere up in the hills....
Skiing the Rutherford and Ryan River drainages, and drainages east of Wasp creek over the past couple of days provided a good look at the state of the backcountry after the most recent storm-cycle that brought almost two-metres of snow to the region.
There was evidence of many old, and large, natural avalanches that occured on all aspects during, or soon after, that storm cycle around December 25th. The strong winds, intense snowfall, and some untrustworthy layering deep in the snowcover helped create an unstable snowpack then. Many avalanches were in the size 2 to 3.5 range and failed as slabs, and on most aspects. Some of these avalanches had propogated over lengthy distances and many had deep crowns.
The characteristics of the terrain, that produced these events, was often steep, rocky, lee, unsupported (slope continuity changes very abruptly) and cross-loaded slopes, although there were many large releases on south-facing alpine terrain, too.
We noticed one natural avalanche that occured yesterday on a steeper convex (rolling) slope on a north-facing piece of glaciated alpine terrain located just below a ridgeline feature. The strong outflow winds during much of yesterday helped build further windslabs in the alpine.
Some of these events were digging deep to a crust and facet layer (that was buried on November 6th) now down anywhere from 1.5m-3m.
Most exposed alpine terrain has been hammered by the recent arctic-outflow winds of the previous two days. The best skiing has been around treeline (all aspects) and below with good-quality cold and loose powder snow. These lower elevations have not been impacted by the strong winds of late. Recent cold temperatures have helped to tighten the snowpack and made it a little more reluctant to being skier-triggered. I would still be careful of recently wind-affected areas, though (parcels of terrain that feel 'slabby').
Creeks are still open in places and many of the crevasses are filled-in, except where those strong winds may have scoured the glaciers.
The November 6th crust and facet layer continues to linger deep in the snowpack and is being triggered by heavy loads (the impact force of a falling cornice, explosives, etc.). That steep, rocky, lee or cross-loaded terrain should continue to be suspect. It feels like this layer, deep in the snowpack, may be with us for a long time, yet. Carefully consider the scale (size) of the terrain that you wish to ski, how the terrain is configured and its characteristics, and if there are any overhead threats.....
Wishing Everyone a very happy new year and lots of good ski-touring in 2011.
Best regards,
Dale Marcoux
ACMG Ski Guide