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Archived

Avalanche Forecast

Dec 30th, 2019–Dec 31st, 2019
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
2: Moderate
The avalanche danger rating below treeline will be moderate
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
2: Moderate
The avalanche danger rating below treeline will be moderate
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Little Yoho.

The avalanche hazard is increasing with the arrival of new snow and wind. We also have a lot of uncertainty about where the deep persistent layer might be triggered. As a result it is a good time to be patient and make conservative terrain choices.

Weather Forecast

A series of systems will reach the forecast region with light snowfall over each of the next few days. Amounts of about 5 cm each day are expected, though some forecasts are much higher. Winds will remain strong in the alpine for Tuesday and start to taper off on Wednesday. Treeline temperatures remain mild and steady between -10 and -5 'C.

Snowpack Summary

New snow and moderate to strong SW winds are creating new wind slabs in lee areas at and above treeline. In many areas the upper snowpack of denser snow sits over a weak mid and lower snowpack consisting of facets, depth hoar and crusts. In deeper snowpack areas these weaknesses are less pronounced. Snowpack depths at treeline average 100-160+ cm.

Avalanche Summary

No new avalanches observed or reported on Monday. Reports of whumpfing, as well as explosive and skier triggered avalanches up to size 2 on the deep persistent layer of facets and depth hoar have occurred in the last several days, and we expect this layer to continue to be problem for a while. A few smaller wind slabs were also reported recently.

Confidence

Forecast snowfall amounts are uncertain

Avalanche Problems

Wind Slabs

Moderate to strong winds and new snow over the next couple days will build wind slabs in lee areas at treeline and above. These will be easy to trigger so avoid lee loaded areas and minimize your time in areas with wind loading going on above you.

  • If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2

Deep Persistent Slabs

Continued reports of whumphfing on the weak, faceted lower snowpack indicate the potential for human triggering. This likelihood will rise with new snow and wind over the next few days. Triggering the deep facets could result in a large avalanche.

  • Minimize exposure to overhead avalanche terrain, large avalanches may reach run out zones.
  • Use careful route-finding and stick to moderate slope angles with low consequences

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2 - 3