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Avalanche Forecast

Archived

Feb 11th, 2013–Feb 12th, 2013

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

Jasper.

Tuesday's avalanche danger will increase if the forecasted frontal passage comes in Monday night instead of Tuesday night.

Weather Forecast

Up to 20cm of snow could fall as a front passes through the area beginning later in the day on Tuesday and continuing through to Wednesday mid day. Temperatures will drop by a few degrees overnight as the front passes and a trailing cold front settles into the area.

Snowpack Summary

Hard windslab is bridging the weak basal facets above treeline.  Field tests in the alpine on a SE windloaded terrain feature produced easy results on a buried surface hoar layer directly below the hardslab. This confirms that there are several weak layers below that the avalanche can slide on.  Below treeline, the mid-pack is weak.

Avalanche Summary

No new avalanches were observed today.

Confidence

Forecast snowfall amounts are uncertain 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.