Avalanche Forecast

Issued: Jan 20th, 2015 8:42AM

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

Avalanche Canada jfloyer, Avalanche Canada

Safe backcountry travel requires caution and good terrain selection at this time. Avalanches have been easily triggered by light loads.

Summary

Confidence

Good

Weather Forecast

Wednesday: Dry. Freezing level around 1000 m. Ridgetop winds 30-40 km/h from the southwest.  Thursday: Light flurries. Freezing level around 1500 m, although local areas, especially in the north of the region, could see higher freezing levels with pockets of warm air. Ridgetop winds around 30 km/h from the southwest.  Friday: At present this region looks like it will stay mostly dry, but models are uncertain with an approaching storm that could bring some snow and/or rain to this region. Strong southwest winds and rising freezing levels likely.

Avalanche Summary

Numerous avalanches were reported to have run during and immediately after the most recent storm. While most avalanches were in the size 1.5 to 2 range and ran on mostly north as east aspects from 1300 m to 2300 m, there were some larger avalanches that initiated in alpine start zones that were reported as size 3 avalanches. In at least one case, an avalanche stepped down to the mid-December weak layer.

Snowpack Summary

Between 30 and 50cm of new snow has fallen since Friday night, and has been distributed by strong winds into deeper, more cohesive deposits in higher wind-exposed terrain. The new snow overlies widespread 10-30mm surface hoar and a sun crust on steep sun-exposed slopes. I would expect continued touchy conditions, especially in areas where the recent snowfall exists as a cohesive slab.The still problematic mid-December surface hoar/crust layer is typically down 90-130cm below the surface. The reactivity of this persistent weak layer appears to be quite variable but still has the potential for large, destructive avalanches in some areas. The layer appears to be the most reactive in the south of the region at and below treeline. In these locations the surface hoar is more likely to sit directly above a hard crust.

Problems

Persistent Slabs

An icon showing Persistent Slabs
A weak layer comprising of feathery surface hoar crystals and on south aspects a crust is buried between 30 and 50 cm below the surface. This layer appears to be widely found in this region and many recent avalanches were triggered on it.
Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Wind Slabs

An icon showing Wind Slabs
Strong recent winds have set up dense pockets of wind slab in exposed lee terrain.
Be cautious as you transition into wind affected terrain.>Highmark or enter your line well below ridge crests to avoid wind loaded pillows.>

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
A weak layer buried mid-December is still producing dangerous avalanches over a month after it was first buried. Particularly for slopes around treeline, there is a danger for a small avalanche to step down to this layer increasing the consequences.
Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Avoid open slopes and convex rolls at treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

3 - 5

Valid until: Jan 21st, 2015 2:00PM

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