Avalanche Forecast

Issued: Apr 30th, 2013 4:00PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Storm Slabs, Loose Dry and Cornices.

A.L. horton, Parks Canada

Jasper.

Good "dust on crust" skiing can be found on moderate terrain at treeline. Watch for the effects of daytime warming such as the snow becoming less supportive and snowballing. Solar warming will rapidly destabilize the snowpack increasing the danger.

Summary

Weather Forecast

A continuation of the cool W & NW upper air flow pattern with strong winds. Temps will drop below freezing overnight in the valley bottom and remain cool at treeline elevations with a freezing level in the afternoon close to 1800m. This will creep higher into the alpine as the weekend approaches. Localized convective snow flurries are anticipated.

Snowpack Summary

40cm of new snow has fallen in the Icefields area since Saturday. This has formed pockets of windslab at and above treeline. Bonding of this slab on Southerly slopes should be considered suspect. Below the new snow thick melt freeze crust layers cap isothermal snow below. Sun crusts extend high into the alpine on South facing slopes.

Avalanche Summary

With limited visibility at and above treeline no recent avalanches observed have been reported. Spindrift loose snow avalanches can be anticipated from steep and rocky terrain at treeline and above. Bonding between the new storm slabs and the old sun crust should be regarded as touchy with the potential of trigger of slab avalanches is possible.

Confidence

Timing or intensity of solar radiation is uncertain on Thursday

Problems

Storm Slabs

40cm of storm snow has fallen in the past 72hrs. West and NW winds have moved this snow onto lee aspects. South facing aspects are particularly likely trigger areas where the bonding of the new snow to the old melt freeze crust is weakest.

Avoid freshly wind loaded features.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

Loose Dry

The recent storm snow will be sluffing off steep terrain as point release avalanches. Typically this is of most concern to alpine and ice climbers who need to be particularly mindful of this hazard under the current conditions.

Avoid travelling on ledges and cliffs where sluffing may have severe consequences.Be very cautious with gully features.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Likely

Expected Size

1 - 2

Cornices

Recent snow and strong NW winds will continue to build cornices. On failure deep releases may run far into the valley bottom. With poor visibility high in the mountains stay well back from potential cornice features above steep drop offs.

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

2 - 3

Valid until: May 1st, 2013 4:00PM