Avalanche Forecast
Issued: Dec 10th, 2019 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
Lisa Paulson,
Parks Canada
Lots of recent snow over a weak base, now being moved by west wind into reactive wind slabs. Stick to conservative lines and allow some time for the snowpack to adjust and bond.
Summary
Weather Forecast
Continued moderate West alpine winds are expected overnight and increase to strong on Thursday. This will add to existing wind slabs and keeping the alpine hazard at Considerable. Temperatures should remain seasonal in the -10 range at tree line. Minimal snow, and a mix of sun and cloud for Wednesday and up to 5 cm on Thursday.
Snowpack Summary
Moderate winds in the alpine are adding to the wind slabs problem in the alpine. Beneath the recent 40-60 cm of recent snow, the snowpack structure is generally weak, consisting of facets and depth hoar. The Nov crust is present up to 2500m and ~30 cm up from ground. Snowpack depths at treeline range from 80-160 cm.
Avalanche Summary
Avalanche control today continues to produce windslab avalanches. Sunday and Monday's control produced up to size 3 avalanches with propagations across terrain features and stepped down to the Nov crust and basal facets. A skier accidental size 2.5 on the basal weakness occurred in West Bowl at Lake Louise Sunday.
Confidence
Problems
Wind Slabs
Recent snow and wind have formed reactive wind in many open areas at treeline and in the alpine. Human triggering of this slab remains possible or even likely in some terrain, though natural avalanche activity has slowed down.
- Caution on open steep slopes at treeline that have been exposed to wind loading.
- Use caution in lee areas. Recent wind loading has created slabs over weaker snow.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
The recent snow sits over weak facet and crust layers. Numerous natural and explosive triggered avalanches up to size 3 have been observed on these weak lower layers in the past several days. Human triggering in steep terrain remains a real concern.
- Be aware of thin areas that may propogate to deeper instabilites.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 11th, 2019 4:00PM
