Avalanche Forecast

Issued: Apr 29th, 2013 4:08PM

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 at treeline elevations on moderate south facing terrain. Watch for signs of daytime heating destabilizing the snowpack. Snowballing is a good example that the time to head home is arriving.

Summary

Weather Forecast

Cool temperatures with an upper elevation NW flow will remain over the area until Wednesday evening. Wind directions and speeds will vary greatly across the range with elevation but will, at upper elevations, be from the NW and moderate. Precipitation amount will be similarly variable with up to 10cm near the Continental Divide at upper elevations.

Snowpack Summary

25-35 cm of moist storm snow is sitting on an isothermal snowpack at treeline.Â Storm slabs 30-50 cm thick are on sitting on the April 25th melt freeze crust in the alpine.Â Cool temperatures will maintain the buried crust at lower elevation until the afternoon . Windslabs can be expected on South and East facing slopes in the Icefields area .

Avalanche Summary

With limited visibility at and above treeline no recent avalanches observed have been reported. Spindrift loss 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

Freezing levels are uncertain on Thursday

Problems

Storm Slabs

30 cm of storm snow has fallen in the past 36hrs. Strong 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.Avoid steep Southerly aspects.

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

Elevations: Alpine, Treeline.

Likelihood

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.

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

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.

Do not travel on slopes that are exposed to cornices overhead.Stay well back from cornices.

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

2 - 3

Valid until: Apr 30th, 2013 4:08PM