Avalanche Forecast

Issued: Nov 26th, 2017 4:25PM

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

Avalanche Canada mgrist, Avalanche Canada

Consider avalanche danger to be HIGH in areas that receive rain on top of 30 cm or more of dry snow. Avoid exposure to avalanche terrain during periods of rapid loading by rain, snow, or wind.

Summary

Confidence

Low - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

We should see a return to more seasonal temperatures this week with small accumulations of snow. MONDAY: Cloudy with isolated flurries. Light to moderate westerly ridgetop winds. Freezing level around 1000 mTUESDAY: 5-10 cm of snow. Light to moderate westerly ridgetop winds. Freezing level around 1500 mWEDNESDAY: Isolated flurries. Moderate westerly ridgetop winds. Freezing level rising around 1200 m

Avalanche Summary

On Saturday we received reports of a skier-triggered Size 1 storm slab on a NW aspect at 2150m elevation in Rogers Pass. See here for the MIN report. A natural avalanche cycle is expected on Sunday into early Monday in areas where rain falls on dry snow. We currently have very limited observations in this region. Please submit your observations to the Mountain Information Network (MIN).

Snowpack Summary

15 to 30 cm of recent snow and moderate to strong southwesterly winds have likely formed wind slabs on lee features at treeline and above. The new snow sits on a thick crust formed by the rain that fell to mountain tops last Wednesday and Thursday. The heavy rains of last week rapidly shrunk the snowpack and has transitioned much of the snowpack from dry to moist snow. The depth of the snowpack varies greatly with elevation. Recent reports suggest the average depth is 200+cm in the alpine, 100-150cm at treeline, and decreasing rapidly below treeline where the primary hazards are rocks, stumps, and open creeks. A major feature in the snowpack is a crust which was formed around Halloween and can be found approximately 70-100cm down at treeline elevations. We currently have very limited snowpack observations within this region and it is critical to supplement this information with your own observations.

Problems

Storm Slabs

An icon showing Storm Slabs
A natural avalanche cycle is expected on Sunday into early Monday in areas where rain falls on dry snow.
Use conservative route selection, choose moderate angled and supported terrain with low consequence.Watch for signs of instability such as whumpfing, cracking, or recent natural avalanches.Avoid exposure to avalanche terrain during periods of rapid loading by rain, snow, or wind.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
Rapid loading by rain or snow will increase the likelihood of avalanches occurring on this layer.
Avoid exposure to avalanche terrain during periods of rapid loading by rain, snow, or wind.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Nov 27th, 2017 2:00PM

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