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Avalanche Forecast

Archived

Mar 14th, 2017–Mar 15th, 2017

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Little Yoho.

A widespread avalanche cycle is underway with many small and large avalanches observed on Tuesday. Avoid exposure to all avalanche terrain. We have published our forecast early today to get this message out there.

Weather Forecast

Strong westerly flow continues as another storm crosses the area starting Tuesday afternoon. By Wednesday end of day we should see 20 cm of additional snow. Freezing levels will remain near 2000m until Wed afternoon when the air will slowly begin to cool. Alpine winds are forecast to be moderate to strong through the period.

Snowpack Summary

Additional snowfall and warming temperatures have tipped the snowpack and an avalanche cycle is underway. A 50 cm dense slab has overloaded two prominent weaknesses in the snowpack; one down 40cm and the other in an faceted layer near the base of the snowpack. We expect the cycle to persist while the temperatures remain warm over the coming days.

Avalanche Summary

Two skier triggered avalanches on the Wapta on Monday evening, and then a flight along the Bow Valley Tuesday morning revealed dozens of fresh avalanches ranging from size 1 to size 3. There is an avalanche cycle underway now.

Confidence

Due to the number of field observations on Tuesday

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.