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Archived

Avalanche Forecast

Jan 18th, 2014–Jan 19th, 2014
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
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Purcells.

Confidence

Fair

Weather Forecast

A ridge of high pressure will continue to dominate the region for the forecast period bringing dry conditions, mainly sunny skies and light winds from the west/northwest. Freezing levels should hover around 1000m for Sunday. Although there's a possibility of an inversion redeveloping for Monday and Tuesday, alpine temperatures are expected to remain just below freezing. No significant precipitation is expected for at least a week.

Avalanche Summary

On Friday explosives avalanche control produced at least 3 size 3 slab avalanches which failed to ground in steeper alpine terrain. 2 size 3, and 1 size 3.5 natural slab avalanches were also noted. At least 2 of these failed at ground level. All avalanches observed failed on a variety of aspects. No avalanche reports from Saturday's warm-up were available at the time of publishing this bulletin.

Snowpack Summary

Between 60cm and 90cm of well settled storm snow exists as a stubborn hard wind slab in many exposed areas. Steep, sun exposed slopes are seeing a daily melt-freeze cycle while surface hoar has been growing in some shaded terrain. Below the recently formed storm slab you may find surface hoar buried around January 8th, although no recent avalanche reports have been attributed to this layer. In the mid to lower pack you may find a surface hoar layer buried in mid December. Further down you may also find the December facet/crust combo. These layers are likely gaining strength, but professional operators are treating them with caution.The biggest concern throughout the region is a layer of weak sugary depth hoar at the base of the snowpack which may coexist with a crust which formed in October. I would continue to be suspicious of any large or unsupported upper elevation slopes, especially if they haven't already avalanched. Possible triggers include a heavy load over a thin spot, a cornice fall or rapid temperature change. Any avalanche failing at this interface would be highly destructive.

Avalanche Problems

Deep Persistent Slabs

I would continue to be suspicious of any large or unsupported upper elevation slopes, especially if they haven't already avalanched. Any deep persistent avalanche would be highly destructive.
Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>Caution around convexities or areas with a thin or variable snowpack.>Be aware of the potential for full depth avalanches due to deeply buried weak layers.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 3 - 7

Wind Slabs

Some operators are still expressing concern for wind slabs that were formed last week. Although they may have gained considerable strength, triggering may still be possible in steep, unsupported terrain.
Be aware of the potential for wide propagations due to the presence of hard windslabs.>Watch for areas of hard wind slab in steep alpine features.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Unlikely - Possible

Expected Size: 1 - 4