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Avalanche Forecast

Archived

Dec 14th, 2014–Dec 15th, 2014

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

Regions

South Rockies.

Danger ratings trending down due to low freezing levels after the recent rain.

Confidence

Fair - Due to the number of field observations

Weather Forecast

Clearing overnight with light Southeast winds and alpine temperatures around -6. Freezing levels should remain at valley bottoms for the forecast period. Sunny with light Southwest winds on Monday. Tuesday mostly sunny with some valley cloud. Cloud moving in to the region on Tuesday evening and remaining on Wednesday. No precipitation expected for the forecast period.

Avalanche Summary

No new reports of avalanches from the region.

Snowpack Summary

Overnight freezing has developed a surface crust up to about 2100 metres and the whole snowpack has re-frozen into a solid mass below about 1600 metres. Early Sunday 10-15 cm (@Harmer weather station) of dry light new snow has buried the crust that was left after the recent rain.  There may be a buried persistent weak layer of crust and/or facets that is now down between 70-100 cm. This buried crust from November may continue to be triggered by large additional loads in high alpine areas that did not get rain during the recent storm. Pockets of wind slab may continue to be triggered by skiers and riders at or near ridgetops in areas where the snow was dry enough to be transported by the strong Southwest winds during the storm.

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.