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Avalanche Forecast

Archived

Jan 11th, 2015–Jan 12th, 2015

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

Regions

Purcells.

Variable reactivity of the mid-December crust/surface hoar interface is driving significant uncertainty. The solution is easy though: Stay disciplined and continue to seek out the most conservative terrain.

Confidence

Fair

Weather Forecast

An upper ridge continues to shift the storm track into the Alaskan Panhandle.  No new snow is expected for the three day forecast period.  Winds are expected to remain very light out of the W/NW at treeline and moderate NW at ridgetop.  The freezing level looks to remain at Valley Bottom until Wednesday afternoon when it is expected to rise as warm SW air begins to invade the province.

Avalanche Summary

No new avalanche activity to report.

Snowpack Summary

There is a great deal of variability across the region. The West and South have received up to 60 cm of storm last week which was quickly followed by high freezing levels and warm air up into the alpine which has resulted in a breakable surface crust. The North and East of the region have had 20-30 cm of cold dry new snow which has since been redistributed into ageing wind slabs, while large surface hoar is growing in sheltered areas. Deeper in the snowpack there is a persistent weak layer of surface hoar and crust that is now down about 30-80 cm. Recent snowpack tests on the West side of the range produced easy resistant results down 25 cm in the recent storm snow, and moderate to hard but sudden results down 80-90 cm on buried surface hoar sitting on a crust.

Problems

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.