Avalanche Forecast

Issued: Apr 10th, 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, Loose Wet and Wind Slabs.

rupert wedgwood, Parks Canada

Jasper.

Good skiing can be found close to treeline on sheltered north facing terrain.

Summary

Weather Forecast

A strong westerly flow to the upper atmosphere will accompany the passage a of weak frontÂ tonight with a dusting of snow. Overnight temps will remain cool and winds will decrease. A mix of sun and cloud adding heat to the snowpack at lower elevations and solar aspects with the freezing levels not expected to breach 1,700m on Wednesday.

Snowpack Summary

In the upper snowpack a 25 to 80 cm thick slab bridges the March 15th persistent weak layer (facets on polar, sun crust on solar). Recent warming has promoted rounding in the upper snowpack, however the mid and lower snowpack remain weak and facetted from this winters prolonged cold periods. Temperature crusts exist on most slopes below treeline.

Avalanche Summary

We received a report of large slab avalanche on Monday in the North bowl of Whistler peak. It was remotely triggered from the ridgetop and failed as a size 2.5 persistent slab (suspect Mar 15th interface), 60cm deep by 75m wide, which ran down to treeline. Some size 1 moist surface sluffing was noted on steep solar aspects on Sunday.

Confidence

Freezing levels are uncertain

Problems

Persistent Slabs

Persistent slabs sitting on facets on Northerly aspects continue to show isolated signs of reactivity. On solar aspects buried solar crusts present a sliding surface up to 80cm down. Triggering may occur from shallow snowpack areas some distance out.

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

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Loose Wet

The snowpack is rapidly heating up and in shallow spots requires very little in the way of rain, sun or ambient heat to complete the process. Snow pillows falling onto snow of this character will trigger avalanches. Solar radiation is a trigger.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 1.5

Wind Slabs

Moderate southerly winds in the alpine continue to build fresh pockets of wind slab. Once started these slabs may trigger deeper releases running surprisingly far into the valley under these cooler conditions.

Use caution in lee and cross-loaded terrain near ridge crests.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 1.5

Valid until: Apr 11th, 2018 4:00PM