Avalanche Forecast
Issued: Nov 30th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Deep Persistent Slabs.
wlewis,
Avalanche Canada
Avoid all avalanche terrain during heavy snowfall and strong winds. Avalanches may run full path and small avalanches may step down to deeper layers.
Summary
Confidence
Weather Forecast
TUESDAY NIGHT: Precipitation continues overnight with 10-25mm with strong to extreme southwest winds. Freezing levels soar above 2000m.
WEDNESDAY: Strong southwest winds with freezing levels remaining above 2000m. 10-30cm is expected over the day with accumulations favouring the Bugaboos.
THURSDAY: Skies clear over the day with flurries tapering off. Winds ease to moderate westerlies. Temperatures drop, with freezing levels falling to valley bottom in the evening.
FRIDAY: Cold and clear with alpine highs around -8. Freezing levels stay below 1000m with light to moderate southwesterly winds.
Avalanche Summary
Monday November 29th saw multiple explosive triggered size 2 storm slabs near Golden. Numerous naturally triggered storm slab avalanches were observed near Toby Creek, up to size 2 from alpine features on north facing slopes. Explosives also produced a size 1 storm slab avalanche confirmed to have failed on the late November surface hoar layer in the Toby Creek area. This layer also produced multiple natural avalanches up to size 2 on Sunday. This surface hoar layer is believed to be widespread in the Toby Creek drainage area above 1600m.
A report on the Mountain Information Network noted a widespread natural cycle was evident in the Quartz Creek area.
Several more storm slab avalanches up to size 1.5 were observed in the Northern Purcells throughout this storm.
Snowpack Summary
Snowfall exceeds 80cm over the last week. More heavy precipitation and sustained strong winds will continue to build storm slabs over recently wind effected snow. Elevated freezing levels over the past week have created moist snow at lower elevations.
A surface hoar layer has been observed down 30 to 40cm in the Toby Creek drainage in wind sheltered features.
The mid-November rain crust exists throughout the region and sits down 30 to 60cm. It generally exists below 1900 m.
Several early season crusts exist throughout the lower snowpack and a late October facet/crust layer of concern sits at the bottom of the snowpack above 1900m. This layer has produced propagating results on recent tests, however data is sparse at this point in the season.
Average snowpack depth at treeline is 100cm - 180cm, with the deepest snowpack found near the Bugaboos.
Terrain and Travel
- Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
- Avoid exposure to overhead avalanche terrain, avalanches may run surprisingly far.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Problems
Storm Slabs
Heavy new snow and wind will build large storm slabs through the day. A natural avalanche cycle is expected with this new and heavy load added to the snowpack. Expect large and destructive avalanches that may run full path into lower elevations.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
A layer of facets exists at the base of the snowpack. These weak crystals continue to be a concern, especially with a heavy load of new snow being added to the snowpack.
We have limited information on the distribution of this layer but suspect it exists at treeline and alpine elevations. Smaller avalanches have the potential to step down to these deeper weak layers, producing large and destructive avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 1st, 2021 4:00PM
