Avalanche Forecast

Issued: Apr 13th, 2018 4:00PM

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

jasper snow safety, Parks Canada

Jasper.

Good skiing can be found close to treeline on sheltered north facing terrain as winter conditions persist. Evaluate specific terrain features before committing. Human triggered avalanches are possible.

Summary

Weather Forecast

Friday into Saturday may bring 8-12cm. Saturday will be cloudy and flurries, trace of snow, high -5, and SW 20km/hr gusting 60 winds, with 1700m freezing level. Sunday will bring flurries, 11cm of snow, low -5 and high -1 C, light SW winds, and 2100m freezing level. Monday will be flurries, 8cm of snow, low -10 and high -2 C.

Snowpack Summary

Wind slabs and wind effect is found in open areas treeline and above. The upper snowpack is a variable 25 to 80 cm thick slab that sits on weak FC crust layers in the mid-pack. Depth hoar persists near the ground.

Avalanche Summary

No patrol Friday. A cornice triggered a size 2.5 slab in Shangrila area today. Skiers released a cornice to test Ullr / terminator chute #5 Wednesday and released a healthy size 2 avalanche on Wednesday. See the MIN report. This is a steep N facing chute dropping into Whistler creek drainage from the backside of Marmot basin.

Confidence

Forecast snowfall amounts are uncertain on Saturday

Problems

Persistent Slabs

A slab up to 80cm thick overlies: weak faceted crystals (well developed in shallow areas), surface hoar (at, and just above treeline), and sun crusts ( on steep S and W aspects). Faceting has reduced slab strength below treeline and in shallow areas.

Avoid steep convexities or areas with a thin or variable snowpack.Carefully evaluate big terrain features by digging and testing on adjacent, safe slopes.

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Wind Slabs

Previous wind effect will be difficult to assess under new snow. Expect hardslabs in the alpine and at treeline. The cold has reduced the tension in these but caution is still warranted, especially as new snow arrives over the next few days.

If triggered the wind slabs may step down to deeper facet layers resulting in larger avalanches.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Cornices

Cornice failure noted in Shangrila on Friday releasing a size 2.5 slab below.

Minimize overhead exposure during periods of heavy loading from new snow, wind.

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1.5 - 3

Valid until: Apr 14th, 2018 4:00PM