Avalanche Forecast

Issued: Mar 10th, 2017 5:57PM

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 Deep Persistent Slabs.

Ruari Macfarlane, Parks Canada

Waterton Lakes.

Recent storm snow has not yet settled. New snow, wind loading and warming temperatures will add to instability. Cornices are large, and could trigger deep layers. This is a time to stick to conservative terrain without overhead hazard.

Summary

Weather Forecast

Current forecasts vary widely- use discretion.Saturday: Sun+cloud, becoming light snowfall in the afternoon. Treeline high -2.5. Temperature inversion. Moderate - Strong SW winds. 10-20cm of snowfall expected Saturday overnight. Sunday: Cloudy. Treeline High -4. Moderate W winds. Mon: Sun & Flurries. Treeline high -1, Moderate-Strong W winds

Snowpack Summary

25 - 40cm of new snow has fallen over Thursday/Friday. Moderate SW winds with near-freezing temperatures above 1800m continue to redistribute these into Storm Slabs, especially on lee slopes. An interface now down 45cm gave Easy, sudden shears on Thursday. Daily snowfall since Feb 25 may be stressing a thick, dense facet layer deep in the snowpack.

Avalanche Summary

On Thursday, a Large Storm Slab avalanche was observed at Treeline(2050m), on a steep, open N aspect below large cliffs. Numerous Small Loose Dry avalanches were observed in steep terrain. A few other slab avalanches (Size 1 -2)were observed in the Alpine, but observations were hampered by visibility. Poor visibility limited observations on Friday.

Confidence

Due to the number of field observations on Friday

Problems

Storm Slabs

Storm Slabs will be touchy. Pay special attention to Treeline and Alpine slopes lee to SW winds - slabs will continue to grow on these slopes. Avoid steep slopes where wind transported snow is being deposited.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.The new snow will require several days to settle and stabilize.

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

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

2 - 3

Loose Dry

These will be a problem in areas sheltered from the wind, especially in confined features, like gullys.

Choose ice climbs that are not exposed to avalanches from above.Be cautious of sluffing in steep terrain, particularly where the debris flows into terrain traps.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Deep Persistent Slabs

There is uncertainty about the distribution of this layer, it is suspected to be most reactive at Treeline, on steep S and SW aspects where facets overlie a crust.

Avoid thin, rocky or sparsely-treed slopes.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 4

Valid until: Mar 13th, 2017 5:00PM