Avalanche Forecast

Issued: Mar 16th, 2015 8:23PM

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

tim haggarty, Parks Canada

Waterton Lakes.

Up high, fresh, thick new storm slabs exist in many start zones: limit your exposure to these until they have some time to settle. Down low, the snowpack is recovering from the heavy rains and will be rapidly effected by any warming.

Summary

Weather Forecast

Freezing levels will rise to 1800m Tuesday with up to 10 cm expected late in the day with light winds. Freezing levels will reach 2000m with West winds Wednesday as the precip tapers off midday. Expect some sun and even higher freezing levels on Thursday with a SW flow bringing warming for the end of the week.

Snowpack Summary

20 to 30 cm of new snow now sits above a rain soaked snowpack to 2000m. At higher elevations the amount of moist snow now buried gets shallower and the new snow amounts grow quickly to 60cm at 2200m. A new rain crust has formed as the moist snow begins to refreeze. NE winds deposited the new snow in a reverse loading pattern along ridge crests.

Avalanche Summary

Visibility has been poor for the last few days but some size 2.5 debris piles can be seen below the clouds in the run-outs in several of our large alpine paths. We suspect the storm snow is failing as a soft slab and running on the new rain crust or entraining the moist snow below. The surface snow sluffs easily with skier traffic in steep terrain.

Confidence

Timing or intensity of solar radiation is uncertain on Thursday

Problems

Storm Slabs

New slabs sitting on a newly formed crust can be found at all elevations but are much more significant at the upper limits of treeline and the alpine. These will be more reactive in steep or unsupported terrain and may be ripe in many start zones.

Be alert to conditions that change with elevation.If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Loose Dry

Skiers in steep terrain can expect the surface snow to sluff. Manage yourself and your group carefully to avoid getting caught by these small avalanches. Avoid terrain where a sluff could trigger a more significant storm slab.

Be very cautious with gully features.Sluffs may trigger deeper instabilities.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 1

Loose Wet

As temperatures increase this week watch for moist snow to develop at lower elevations where most of the snowpack has yet to refreeze. If the sun comes out this will happen quickly on solar slopes.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Mar 19th, 2015 4:00PM