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Archived

Avalanche Forecast

Nov 29th, 2017–Nov 30th, 2017
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
1: Low
The avalanche danger rating below treeline will be low
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

Regions: Purcells.

This forecast is based on very few field observations and a high level of uncertainty exists. Conservative terrain selection remains critical until we get a better handle on the snowpack

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Thursday: 5-15cm of new snow / Strong southwest winds / Freezing level at 900m Friday: Light flurries / Light southerly winds / Freezing level at 900mSaturday: Mix of sun and cloud / Light southerly winds  / Freezing level at 900m

Avalanche Summary

On Tuesday explosives control in the north of the region triggered a few size 2 storm slabs in north-facing alpine terrain. On the same day in the Dogtooth range a skier was accidentally caught in a size 2 storm slab on a northwest facing slope at 2350m. The skier was uninjured in the avalanche which was about 40cm deep and 180m long..We currently have very limited observations in this region. Please submit your observations to the Mountain Information Network (MIN).

Snowpack Summary

Last week, the November 23rd crust formed as temperatures cooled and the rain-soaked snow surface froze. Since then, 15-50cm of snow has fallen at treeline and above with moderate to strong southwest winds, creating wind slabs sitting on a crust. Two other layers have been reported in the snowpack: 1) The Halloween crust (down 100cm at treeline elevations) and 2) The November 10th surface hoar / facets (down 80cm at treeline elevations). We have very little information on how reactive these layers are. In fact, we currently have very limited snowpack observations within this entire region and it is critical to supplement this information with your own observations.The depth of the snowpack varies greatly with elevation. Recent reports suggest the average depth is 150+cm in the alpine, 100-150cm at treeline, and decreasing rapidly below treeline where the primary hazards are rocks, stumps, and open creeks.

Avalanche Problems

Storm Slabs

New wind and snow on Thursday will form reactive new storm slabs. Storm slabs may be larger than expected in heavily wind-exposed terrain, or in areas where underlying crusts remain reactive.
Watch for signs of instability such as whumpfing, cracking or recent natural avalanches.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 3