Avalanche Forecast
Issued: Dec 20th, 2020 6:07PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
Mark Herbison,
Winds are expected to taper off moving into Monday, but the wind slabs will still be there waiting for you.
Summary
Weather Forecast
Another 2-5cm of snow by Monday morning with an additional 5-15cm by Tuesday morning. Winds will drop off drastically and switch to the East as temps will range from -4 in the valley to -15 at ridge top.
Snowpack Summary
20cm of snow in the past 24hrs brings the storm total to 30-60cm. Winds slabs forming in the alpine down into tree line from strong West winds. The Dec 13 and Dec 7 sun crust/surface hoar/facet layers are down ~ 35cm and ~65cm respectively. The decomposing Nov crust/facets sits at the bottom of the snowpack. Height of snow at tree line is 80-150cm.
Avalanche Summary
A widespread natural cycle across the region today with avalanches up to sz 2.5, most notably Bourgeau Left Hand, dusting valley bottom for the second day in a row. Local ski areas were ski cutting wind slabs up to sz 1.5 and had explosive results up to sz 2.
Confidence
Problems
Wind Slabs
Wind slabs are expected in the alpine and down into tree line with previous strong Westerly winds and snow available for transport . In steep avalanche paths and gullies these have the potential to run down below treeline entraining facets.
- Use caution in lee areas. Recent wind loading has created wind slabs.
- If triggered the wind slabs may step down to deeper layers resulting in large avalanches.
Aspects: North, North East, East, South East, South, South West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
The Nov 5 crust has facets above and below it and exists up to 2500m on shady aspects and higher on solar aspects. We have limited observations of deep slab avalanches recently, but the gradually increasing snow fall amounts may change this.
- Be aware of thin areas that may propogate to deeper instabilites.
- Pay attention to overhead hazards like cornices which could trigger the deep persistent slab.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 21st, 2020 4:00PM
