Avalanche Forecast

Issued: Dec 16th, 2013 9:01AM

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

danyelle magnan, Parks Canada

Glacier.

A widespread avalanche cycle is ongoing. Large avalanches are reaching the end of their runouts. Conservative terrain choices (tree skiing) and avoiding exposure to overhead avalanche hazard are highly advised.

Summary

Weather Forecast

Light to moderate precip is forecast today with strong to extreme westerly winds at ridgetop. A warm front will pass through the region overnight bringing moderate to heavy precip, with another 15-20cm and sustained winds expected through Tues. Snowfall and winds should taper off through Wed as an arctic ridge builds through Thursday.

Snowpack Summary

Nearly 70cm of snow has fallen in the last week, with 35cm over the past 2 days. Winds have increased overnight, rapidly loading lee slopes and forming windslabs in the alpine. There are several reactive layers in and below the storm snow. The Nov 28 persistent weak layer is down 70 and gives sudden planar results in snowpack tests.

Avalanche Summary

A widespread natural cycle and avalanche control are ongoing. Natural avalanches size 2.5 to 3.5 have been occurring from all aspects and running to the end of their runout zones. Several avalanches were reported from skiers up Connaught yesterday, running off of Mt Cheops and to within 20m of the uptrack on the other side of the valley.

Confidence

Problems

Storm Slabs

As the storm continues to dump snow, with strong winds and warm temps, the storm slab is becoming deeper and more cohesive. There are reactive layers within and at the base of the slab that are likely to be triggered by skiers.

Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.Good group management is essential to manage current conditions safely.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

The storm has rapidly loaded slopes and may overwhelm persistent weak layers buried deeper in the snowpack. Very large avalanches will result if these layers are triggered.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 4

Wind Slabs

Strong to extreme SW'ly winds will be forming windslabs and cornices at treeline and above.

Minimize exposure during periods of heavy loading from new snow, wind.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Dec 17th, 2013 8:00AM