Avalanche Forecast

Issued: Jan 21st, 2015 7:49AM

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

Avalanche Canada jfloyer, Avalanche Canada

Safe backcountry travel requires caution and good terrain selection at this time.

Summary

Confidence

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

Weather Forecast

Thursday: Light flurries. Freezing levels rising to around 1400 m. Ridgetop winds 20-30 km/h from the southwest.  Friday: Light snow the afternoon. Freezing levels around 1200 m, ridgetop winds rising to 40 km/h from the southwest.  Saturday: light to moderate precipitation starting in the afternoon currently looks to be around 5 mm. With freezing levels heading as high as 2200 m, this will likely fall as rain well into alpine areas.

Avalanche Summary

Avalanches up to size 2 were reported to have run during and immediately after the most recent storm on all aspects and at elevations from 1800-2300 m. Most avalanches were running on the most recent layer of surface hoar, with typical crown depths of 30-60 cm. There was one report of an avalanche on the more deeply buried mid-December weak layer, although it appears as though it may have been triggered in a shallow spot, as the crown depth was reported to be only 30-45 cm.

Snowpack Summary

Between 15cm and 40cm of recent snowfall has buried widespread 10-20mm surface hoar and a sun crust on steep sun exposed slopes. Strong winds have blown these accumulations into deeper deposits in higher elevation terrain. Due to the underlying surface hoar, I would expect continued touchy conditions, especially in areas where the recent snowfall exists as a cohesive slab.The mid-December surface hoar/crust layer is typically down 60-120cm 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 at and below treeline. The mid-Nov weak layer is near the bottom of the snowpack but has generally become inactive.

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 25 and 45 cm below the surface. This layer appears to be widely found in this region and many recent avalanches were triggered on it.
Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 5

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 thin areas that may propogate to deeper instabilites.>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 22nd, 2015 2:00PM