Avalanche Forecast
Issued: Nov 27th, 2011 9:00AM
The alpine rating is Wind Slabs, Persistent Slabs and Storm Slabs.
, the treeline rating is , and the below treeline rating is Known problems includeSummary
Confidence
Fair - Due to limited field observations
Weather Forecast
A ridge of high pressure should bring a mix of sun and cloud and light winds to the area on Monday. The freezing level should be around 600m. A weak system is forecast to bring increasing cloud and light snowfall on Tuesday (5-10cm) with a freezing level around 600-800m. On Wednesday expect a mix of sun and cloud and slightly warmer temperatures as another ridge becomes established.
Avalanche Summary
There have been few observers in the field during the storm but it is likely that a very widespread and large avalanche cycle occurred throughout the region on Saturday and into Sunday. One report mentioned hearing about large avalanches at all elevations, several of which ran full path to valley bottom runouts at 200-300m elevation. Natural avalanche activity should ease off early this week, but the potential for human triggered avalanches remains. Check out the Nov. 23rd post in the Forecaster's Blog for tips on how to manage risk immediately after a storm.
Snowpack Summary
Recent strong and shifting winds have created a variable snow surface and pockets of deep and dense wind slabs in exposed areas. Fluctuating freezing levels and heavy precipitation will likely produce various storm snow weaknesses. There is a persistent weakness of facets associated with a crust around 40-70cm above the ground. This weakness exists at treeline and alpine elevations and has been sensitive to human triggers. Several recent avalanches on this interface have shown very wide propagation and there have been cases of triggering from a distance. In some areas there is also a factet/crust layer just above the ground. This layer may still be a concern in areas with smooth underlying ground.
Problems
Wind Slabs
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Storm Slabs
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Nov 28th, 2011 8:00AM