Avalanche Forecast

Issued: Dec 3rd, 2021 4:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is low. Known problems include Storm Slabs and Deep Persistent Slabs.

Tim Haggarty,

Email

We are out the other side of the storms with a blast of cold and clear but slabs remained reactive to explosive control Friday. Expect a low on Saturday to stir things up again particularly as west winds start to redistribute the recent snow.

Summary

Weather Forecast

Friday night will bring overnight low temperatures approaching -20C at treeline with almost calm winds. Saturday, expect a low pressure system to affect the region as light precip starts in the morning and  temps warm to -10C midday. Alpine winds will build from the southwest and may reach strong before shifting NW late in the day.

Snowpack Summary

The storms from the end of November and first days of December brought up to a meter of settled snow at treeline and periods of rain as high as 2200m. Cold temps starting Thursday afternoon froze low elevation snow. The snow from these storm sits on the Nov.15 interface (a crust below 2100m) and the Nov. 5 crust/facet layer found near the ground.

Avalanche Summary

With Thursday's clearing and avalanche control flights we have seen widespread evidence of a natural cycle up to sz 4. Many of these started as full depth avalanches in the alpine and resulted in loose wet debris piles at valley bottom. Avalanche control has produced storm slabs averaging 50-100cm deep as well as full depth slabs treeline and above

Confidence

Timing, track, or intensity of incoming weather system is uncertain on Saturday

Problems

Storm Slabs

An icon showing Storm Slabs

Soft slabs can be found treeline and above and these continued to be reactive to explosives 50 to 100cm deep Friday. More wind effect is evident in the alpine as is recent cornice development.

  • If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1.5 - 3

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

Explosives continued to produce slabs on the Nov 5 crust/facets Friday. Some slabs have initiated on this layer, while others were "step down" avalanches triggered as storm slabs or cornices failures hit them.

  • Be aware of the potential for full depth avalanches due to deeply buried weak layers.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3.5

Valid until: Dec 4th, 2021 4:00PM