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Avalanche Forecast

Archived

Dec 16th, 2015–Dec 17th, 2015

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Rockies.

Wind slabs in exposed areas are the biggest concern right now. Easily avoided, especially if you have avalanche training.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Thursday should stay dry during the day, with light snow starting late in the afternoon. Winds light from the southwest and treeline temperatures around -10C. On Thursday night, 5-10 cm new snow is expected with another 5 cm anticipated during the day on Friday. Ridgetop winds 40-70 km/h from the southwest, temperatures climbing to around -3C in the afternoon. On Saturday, flurries, light winds and temperatures around -8C.

Avalanche Summary

On Monday, a couple of size 2 avalanches were reportedly triggered by skiers in steep north and northeast facing slopes. Over the weekend, explosives and ski cutting produced storm slabs size 1-2 which were typically 20-60cm thick.

Snowpack Summary

The series of recent storms has left us with around 40-60 cm new snow sitting on a firm rain crust. For the most part, the new snow has bonded well to this rain crust, although potentially unstable wind slabs could exist where wind-pressed snow rests directly on a slippery crust below. A previous weak layer from early December consists of crust, surface hoar, and/or facets and is typically down 70-90cm. Around 20-30cm below this interface is a rain crust from mid-Nov with a thick layer of facets below it. Both the early-Dec and mid-Nov layers have become dormant and are likely being capped at treeline and below by the more recent rain crust layer. However, these layers may still be reactive to heavy triggers such as cornices, explosives, or smaller avalanches stepping down.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.