Avalanche Forecast

Issued: Apr 10th, 2013 8:00AM

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

Parks Canada Sylvia Forest, Parks Canada

A substantial storm is expected today, with high SW-NW winds and up to 25mm of precipitation.  This will bump hazard up to HIGH tomorrow in the alpine, but be aware that it could get there later today.

Summary

Weather Forecast

A Pacific frontal system will bring moderate precipitation and strong winds to the area today.  Winds will shift from SW to NW throughout the day, potentially resulting in reverse loading of snow onto south aspects.  Expect thick cloud and mild temperatures.  Tomorrow should be a nicer day, drier, maybe even some sun.

Snowpack Summary

Variable Conditions.  In the alpine, SSL and HSL from last weeks storm and wind event overly crusts on solar aspects and facets or surface hoar on north aspects.  The SH (from April 4)  is best preserved above 2400m, and is reactive to skier triggering.  Below treeline, the snowpack has become isothermal, frozen in the mornings, mush by afternoon.

Avalanche Summary

A few isolated avalanches were noted yesterday, and reports of "whumping" by skiers, mostly in the alpine.  Glide cracks and cornices are growing larger, and are failing unpredictably.  Three days ago, a size 3.0 natural slab avalanche in Youngs Peak Basin and a skier remotely triggered size 2.5 - 3 off of Youngs Peak Headwall. 

Confidence

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

Problems

Wind Slabs

An icon showing Wind Slabs
Hard and Soft Slabs were observed in the alpine, near ridge crests and on convexities, all aspects.  Additional snow and wind today will add to this problem
Avoid travelling in areas that have been reverse loaded by winds.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 3

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Glide cracks, gaping cracks in the snowpack, exist on many slopes and have been failing with the warm temps. They can fail unpredictably and release the entire snowpack to the ground.
Be aware of thin areas that may propogate to deeper instabilites.Give cornices a wide berth when travelling on or below ridges.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Persistent Slabs

An icon showing Persistent Slabs
Weak shallow areas are most sensitive.  The character is stubborn to trigger, but seems to result in wide propagations (big avalanches), and is susceptible to remote triggering. 
Travel early before the heat of the day, and avoid big slopes in the afternoon.Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 3

Valid until: Apr 11th, 2013 8:00AM