Avalanche Forecast

Issued: Jan 27th, 2016 8:15AM

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

triley, Avalanche Canada

Purcells.

Warm, Wet, and Windy storm will create new wind slabs and add load above the persistent weak layer. Conservative terrain use recommended at this time.

Summary

Confidence

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

Weather Forecast

Light snow with southwest winds increasing to strong overnight. Freezing level around 1500 metres overnight and rising to about 1700 metres on Thursday. 5-10 cm of new snow with strong southwest winds on Thursday. Winds decreasing to moderate westerly combined with light snow and dropping freezing levels on Friday. Overcast with flurries and light winds on Saturday.

Avalanche Summary

Some skier controlled wind slab avalanches up to size 1.5 were reported on Tuesday from various alpine aspects. One size 2.0 avalanche released sympathetically to a skier controlled avalanche. No new natural avalanche activity was reported. I suspect that wind slabs have continued to develop in the alpine and at treeline on Wednesday.

Snowpack Summary

Most areas are reporting new wind slabs that are 10-25 cm deep, that have developed from moderate to strong southwest winds. Old storm snow amounts are variable across the region from 30-60 cm, and continue to produce settlements and moderate sudden planar test results. The early January persistent weak layer of buried surface hoar continues to be a concern for human triggered large avalanches. Reports indicate this persistent weak layer is now typically down 40-70 cm in most areas and appears to be quite touchy in some parts of the region. A more deeply buried layer of surface hoar from December is now considered dormant. In general, the lower snowpack is well settled and strong.

Problems

Wind Slabs

Wind slabs should continue to develop with forecast new snow and strong southwest winds. New cornice growth may be fragile and easy to trigger.

Be cautious as you transition into wind affected terrain. >Use ridges or ribs to avoid pockets of wind loaded snow. >Avoid freshly wind loaded features. >

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

Natural avalanche activity on this layer may have ended, but this layer continues to be a concern for human triggering. Remote triggering and long fracture propagations are likely with this weak layer.

Be aware of the potential for remote triggers and wide propagations due to a layer of buried surface hoar. >Avoid open slopes and convex rolls at and below treeline, and north-facing alpine slopes, where buried surface hoar may be preserved. >

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 5

Valid until: Jan 28th, 2016 2:00PM