Archived

Avalanche Forecast

Feb 3rd, 2017–Feb 6th, 2017

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

4: High

The avalanche danger rating in the alpine will be high

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

3: Considerable

The avalanche danger rating below treeline will be considerable

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

3: Considerable

The avalanche danger rating below treeline will be considerable

Regions: Waterton Lakes.

Heads Up. Conditions are changing rapidly. Forecaster confidence is low, as forecast snowfall totals vary widely. Avalanche danger will vary accordingly, and so should your plans.

Weather Forecast

Moist, mild Pacific air collides with a cold Arctic High. Forecasts predict anywhere from 40-140cm of snowfall by Monday evening. Alpine winds are mainly moderate SW (Strong on Sunday AM). Below Treeline, a cold Upslope flow with light NE windsprevails (except for Moderate SW winds Sunday AM), causing a temperature inversion. Monday looks frigid.

Snowpack Summary

Substantial new snowfall from Friday to Monday falls on wind-hardened snow, or pockets of very hard wind slab in open areas, 5-15cm thick. In some places this overlies a thin weak layer, seeming especially pronounced at the transition from sheltered to open terrain. The lower snowpack facets have produced isolated Sudden results in snowpack tests.

Avalanche Summary

No new avalanches have been reported or observed at this time (5PM Friday). At Treeline on Thursday, shooting cracking from ski tips were observed in very hard Wind Slab, 15cm deep.

Confidence

Forecast snowfall amounts are uncertain

Avalanche Problems

Storm Slabs

This problem will grow throughout the forecast period, and may be widespread. Pay attention to obvious signs of instability, do snowpack tests on representative slopes, and only expose one at a time. Conservative decision-making is essential.

The new snow will require several days to settle and stabilize.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 2 - 3

Deep Persistent Slabs

Deeply buried Persistent weak layers from a cold winter have produced few results in recent testing, but are now being heavily loaded. In sheltered/windward terrain, this is the first large load on these layers. Avoid previously shallow areas.

Be aware of the potential for wide propagations.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2 - 3

Loose Dry

Loose Dry avalanches will fail naturally in steep sheltered area. These will grow in size by Monday. Avoid extended time in features like gullies Below Treeline, where you will be exposed to overhead hazard, and avoid skiing above your partner.

Choose ice climbs that are not exposed to avalanches from above.Sluffs will be easy to trigger in steep terrain that is sheltered from the wind

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely - Very Likely

Expected Size: 1 - 2