Avalanche Forecast

Issued: Dec 13th, 2013 8:11AM

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

Parks Canada catherine brown, Parks Canada

Minimize exposure to overhead avalanche terrain, large avalanches may reach run out zones.

Summary

Weather Forecast

There is a break in between storms today, with only trace amounts of snow forecast, alpine temps rising to -3 and ridge top winds SW-20 gusting to 60 km/h. Freezing levels today will be ~1200m. The next system will hit the park on Saturday, expect around 5 cm of snow on Saturday and Sunday.  Snow continues through the forecast period till Tuesday.

Snowpack Summary

35-45cm of storm snow sits over the December 8 surface hoar layer at lower elevations and over variable wind slabs up high. The storm snow is mainly low density with some soft slab developing as temps warm. The November 28 surface hoar layer is down around 50-65cm over a facetted mid-lower snowpack. The Nov 12 surface hoar layer is down 70-120cm.

Avalanche Summary

4 size 2-2.5 natural slab avalanches were observed from steep terrain off Mt Tupper and Mt MacDonald on the highway corridor. One natural avalanche, size 3 was also observed yesterday from a north aspect, likely triggered by wind loading. Sluffing of the low density surface snow was observed in unsupported terrain, steeper than 35 degrees.

Confidence

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

Problems

Storm Slabs

An icon showing Storm Slabs
Slabs are forming in over 40cm of storm snow.  Use caution in terrain over 30 degrees. Rider triggering is possible.  Fast sluffing is likely and will pick up large amounts of snow.  Avoid exposure to terrain traps.
Make observations and assess conditions continually as you travel.Parking, eating lunch, and regrouping in runout zones is bad practice.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Wind Slabs

An icon showing Wind Slabs
Watch for soft slabs on lee features at and above tree-line. Large amounts of light snow will be transported by SW winds.
Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
A weak layer buried in early November is present at the bottom of the snowpack. If you are able to trigger the weak layer, a large consequence avalanche will result.
Be aware of thin areas that may propogate to deeper instabilites.Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

3 - 4

Valid until: Dec 14th, 2013 8:00AM