Avalanche Forecast

Issued: Apr 16th, 2017 4:49PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Cornices and Wind Slabs.

jsmith, Avalanche Canada

Purcells.

Minimize exposure to slopes with large cornices overhead when it is cool and cloudy and completely avoid them if it is warm and/or sunny.

Summary

Confidence

High -

Weather Forecast

MONDAY: Cloudy with isolated flurries. Light southwesterly ridgetop winds. Freezing level around 2000m.TUESDAY: Cloudy with flurries. Light to moderate southwesterly ridgetop winds. Freezing level around 2000m.WEDNESDAY: Mix of sun and cloud. Light to moderate southwesterly ridgetop winds. Freezing level rising to around 2200 m.NOTE: The convective flurries which are common during this time of year can result in widely varying snowfall amounts throughout a region. These spring squalls routinely drop 20+ cm of snow in one valley while the adjacent drainage remains dry. For this reason, the distribution of avalanche problems associated with new snow, such as wind slabs, can vary greatly within a region.

Avalanche Summary

On Saturday, several explosive triggered large cornices did not trigger slabs as they slid down steep slopes and a couple did trigger slabs up to size 2.5. Additionally, a couple skier triggered wind slabs on northeast aspects were reported up to size 1.5.

Snowpack Summary

Triggering large avalanches on facets near the bottom of the snowpack is currently our primary concern. On high north facing terrain which is currently where the best skiing can be found, the problem is the possibility that if a large cornice falls on a steep slope, it will trigger this layer. On solar aspects, the problem is small loose wet or wind slab avalanches stepping down to this layer or skier triggering the layer by hitting a shallow spot in a large, steep, and rocky alpine face. Additionally, lingering wind slabs formed by recent snow and wind on lee features at Treeline and above continue to be reactive to human triggers.

Problems

Cornices

Minimize exposure to slopes with large cornices overhead when it is cool and cloudy and completely avoid them if it is warm and/or sunny.

Cornices often break further back than expected; give them a wide berth when traveling on ridgetops.Cornice failures could trigger large avalanches on sugary facets near the bottom of the snowpack.

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Wind Slabs

Small wind slabs may still be reactive to human triggers in isolated locations below ridgetops.

Be cautious with wind loaded pockets near ridge crests and roll-overs.Use ridges or ribs to avoid pockets of wind loaded snow.

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Valid until: Apr 17th, 2017 2:00PM