Avalanche Forecast

Issued: Dec 20th, 2017 8:00AM

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

percy woods, Parks Canada

Glacier.

A touchy surface hoar layer below the recent storm snow has heightened the chance of skier triggered slides. It is a good time for conservative terrain choices.

Summary

Weather Forecast

Sunny with cloudy periods, a trace of snow and alpine temperatures in the -12C range. Thursday should give us light flurries, moderate westerly wind and alpine temperatures of -10C.

Snowpack Summary

40cm of storm snow sits on top of the Dec 15 surface hoar/persistent weak layer. On steeper solar aspects this layer is a crust and/or a crust with small surface hoar on top. The crust runs well up into the alpine on steep south aspects. Deeper in the pack there are a series of crust layers that are currently well bonded to neighboring layers.

Avalanche Summary

A natural avalanche cycle has been continuing over the last 48hrs with over 40 avalanches up to size 3 recorded in the highway corridor. Most slides have been in the size 1.5 to 2 range failing on the Dec 15th surface hoar layer. Avalanches have been on all aspects and elevations including numerous below treeline events.

Confidence

Forecast snowfall amounts are uncertain on Thursday

Problems

Storm Slabs

Recent storm snow continues to settle into a slab. Expect the slab to be increasingly sensitivity as you transition into wind effected terrain. Steeper solar slopes harbor a thin crust layer below the storm snow and a facet surface hoar combo BTL.

Watch for whumpfing, hollow sounds, and shooting cracks.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Wind Slabs

Moderate gusting to strong N-NE winds have been forming reverse loaded windslab in wind exposed areas at and above treeline. These slabs may have surface hoar or crust underneath leading them to be sensitive to human triggering.

Be cautious as you transition into wind affected terrain.Make observations and assess conditions continually as you travel.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Dec 21st, 2017 8:00AM