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Archived

Avalanche Forecast

Jan 19th, 2013–Jan 20th, 2013
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
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
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
1: Low
The avalanche danger rating at treeline will be low
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Jasper.

Winds have raked the landscape and not much left for winds to move. Good skiing is hard to find. If freezing levels are higher than forecasted for Monday, the danger rating may rise correspondingly. 

Weather Forecast

Sunday: ridgetop winds NW 40km/hr, surface freezing level with light snow. Monday: NW 75km/hr, 1900m freezing level, no snow and cloudy periods but mainly sun. Tuesday: SW 25km/hr, afternoon freezing level 1400m and no snow. 

Snowpack Summary

Extreme NW winds have stripped alpine and tree line fetch zones. Hard wind slabs are present on treeline and above lee slopes. Buried surface hoar is found at some locations 10-40cm down depending on windloading patterns. Weak basal facets dominate thin areas. Below tree line, the old storm snow is moist over rotten facets.

Avalanche Summary

On Friday, in the Whistler's area, numerous full depth natural slab avalanches occurred on thin, steep, lee alpine slopes. In the days preceding, we were seeing up to size 3 from wind loading. They were running far in paths with steep run outs. Saturday's patrol no new avalanches were observed on hy 93 as  slightly cooler temps helped to stabilize.

Confidence

Freezing levels are uncertain on Monday

Avalanche Problems

Wind Slabs

Wind slabs have developed on a variety of lee aspects overlying a buried surface hoar in locations from Jan 6th. Avalanches have been observed on thin, steep, lee slopes in the alpine some with wide propagations or stepping down.
Carefully evaluate and use caution around thin snowpack areas.Be aware of the potential for wide propagations due to the presence of hard windslabs.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3

Deep Persistent Slabs

Wind slabs avalanches have triggered this weakness thus gaining significant mass. This situation will more likely occur in shallow snowpack areas. Less activity today due to cooler temperatures but expect some steep slopes remain primed. 
Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2 - 4