Avalanche Forecast

Issued: Nov 28th, 2017 3:59PM

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

Avalanche Canada mgrist, Avalanche Canada

New snow and southerly winds will be driving avalanche danger on Tuesday into Wednesday. Avoid exposure to avalanche terrain during periods of rapid loading by rain, snow, or wind.

Summary

Confidence

Low - Intensity of incoming weather systems is uncertain

Weather Forecast

We're looking at a brief lull in the active weather pattern on Wednesday, before the next system arrives on Thursday with modest amounts of snow.WEDNESDAY: Clearing throughout the day. Moderate westerly ridgetop winds. Freezing level around 1200 m.THURSDAY: Snow (10-15 cm). Moderate southwesterly ridgetop winds. Freezing level around 1000 m. FRIDAY: Cloudy with sunny breaks during the day and isolated flurries. Moderate south west ridgetop winds. Freezing level around 1000 m.

Avalanche Summary

On Monday, several storm slabs to Size 2.5 were reported near Rogers Pass, on northerly aspects between 2000 - 2700m. 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

The warm temperatures and rain on Sunday resulted in a crust (November 27th crust) up to approximately 1900m (higher in the Monashees), which was covered by 5 - 20 cm of snow at higher elevations as temperatures cooled significantly. This November 27th crust could prove to be an excellent sliding layer when additional snow falls on Tuesday into Wednesday. Lower down in the snowpack, 15 to 30 cm of snow sits on a 2-4cm thick crust formed on November 23rd. The heavy rain last week rapidly shrunk the snowpack and 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 3-5 cm thick 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 Tuesday into Wednesday with the incoming snow. Be particularly cautious where the November 27th crust is prominent and more than 25cm sits on it.
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: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Nov 29th, 2017 2:00PM

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