Avalanche Forecast

Issued: Nov 24th, 2017 3:57PM

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

Avalanche Canada cgarritty, Avalanche Canada

Even as storm slabs begin to stabilize, the presence of a more deeply buried weak layer continues to demand conservative terrain selection.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

Saturday: Mainly cloudy with isolated flurries and a trace to 5 cm of new snow. Light to moderate southwest winds. Alpine temperatures around -7.Sunday: Cloudy with flurries bringing approximately 7 cm of new snow. Moderate southeast winds. Alpine temperatures of -5.Monday: Mainly cloudy with isolated flurries and a trace of new snow. Strong southwest winds. Alpine temperatures around -6.

Avalanche Summary

One report from Wednesday discussed several estimated Size 2.5-3 avalanches observed on the Kathlyn face of Hudson Bay Mountain. No other new avalanches have been reported, which likely owes more to a lack of observers than a lack of avalanche activity and potential. Please post your observations to the Mountain Information Network. (MIN)

Snowpack Summary

Snowpack depths over the region are above average for late November, with approximately 150 cm of settled snow present at treeline elevations and above. Stormy weather over the mid-week delivered about 35 cm of new snow to the region, forming storm slabs which are expected to be particularly reactive in open terrain where wind effects are more pronounced. Mid-treeline and lower elevations did receive some precipitation as rain toward the end of the most recent storm, but his thin rain layer is not expected to offer much bridging strength to the snowpack. About 20-30 cm of recent storm snow lies below this week's accumulations and above the widespread late October crust. This October crust is present near the base of the snowpack at all elevations and features a layer of weak, sugary grains above it. This "crust/facet combo" layer remains an ongoing concern for step-down potential from large triggers such as a storm slab release. The crust is less of a concern below treeline where it is broken up by vegetation near the ground.

Problems

Storm Slabs

An icon showing Storm Slabs
Recent stormy weather formed storm slabs that may remain reactive on Saturday. These storm slabs are widespread but you can expect them to be especially reactive at higher elevations and in wind affected areas with more variable snow distribution.
Avoid steep convexities and areas with variable snow distribution.Use extra caution in lee areas in the alpine and treeline. Storm snow has formed touchy slabs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
A crust that formed in October exists near the base of the snowpack and a layer of weak, sugary snow has developed above it. This layer may react to a heavy trigger such as a storm slab release. This would produce a large, destructive avalanche.
Be aware of the potential for large avalanches due to weak layers at the base of the snowpack.If triggered, storm slabs may step down to deeper layers and result in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Nov 25th, 2017 2:00PM