Avalanche Forecast

Issued: Nov 25th, 2017 4:12PM

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

jsmith, Avalanche Canada

Purcells.

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 - Freezing levels are uncertain

Weather Forecast

SUNDAY: 5-15mm rain or snow depending on elevation / Strong westerly ridgetop winds / Freezing level rising to around 2200 m in the northern portion of the region and 2500 m in the south.MONDAY: Cloudy with isolated flurries / Moderate to strong westerly ridgetop winds / Freezing level around 1000 mTUESDAY: 5-10 cm of snow / Moderate to strong westerly ridgetop winds / Freezing level around 1500 m

Avalanche Summary

On Friday, no new avalanches were reported in this region. Natural avalanche cycle expected on Sunday 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

A new crust was formed on Thursday as temperatures cooled and the rain soaked snow surface froze and then was covered by 15-25cm of snow at treeline and above. The new snow has created fresh storm slabs sitting on a crust. The depth of the snowpack varies greatly with elevation. Recent reports suggest the average depth is 150+cm in the alpine, 100-150cm at treeline, and decreasing rapidly below treeline where the primary hazards are rocks, stumps, and open creeks. The major feature in the snowpack is a crust which was formed around Halloween can be found approximately 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

Natural avalanche cycle expected on Sunday in areas where rain falls on dry snow.

Avoid exposure avalanche terrain during periods of rapid loading by rain, snow, or wind.Watch for signs of instability such as whumpfing, cracking, or recent natural avalanches.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Loose Wet

Rain falling on dry snow can quickly trigger natural avalanches.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 2

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 26th, 2017 2:00PM