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Avalanche Forecast

Archived

Mar 12th, 2016–Mar 13th, 2016

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

Regions

Little Yoho.

While the recent wind effect may become obscured with incoming snow Saturday evening and Monday, expect furthrer windslab and cornice development to keep alpine and treeline hazard elevated into the middle of the week.

Weather Forecast

Following freezing levels near 2000m and a warm, gusty, wave of precip Saturday evening, temperatures should drop overnight with freezing levels only reaching 1400m for Sunday under a weak, dirty ridge. Up to 10cm is expected to arrive with moderate winds at treeline Monday however with a 1400m freezing level, rain is possible at valley bottom.

Snowpack Summary

Widespread wind effect treeline and above with 20 to 35 cm of new snow sitting on a well settled mid and lower pack. This new snow overlies a temperature crust below 1800m on polar aspects and a sun crust into the alpine on solar aspects. No significant shears found in the mid and lower pack, however thin snowpack areas are still suspect.

Avalanche Summary

Numerous loose wet slides up to size 2 out of steep terrain below treeline in Little Yoho with limited activity at higher elevations. Numerous natural avalanches observed in the Alpine on the 93N on 93S up to size 3 all aspects following the storm on Thursday. Most of this was triggered by wind loading with failures on crusts and the deep facets.

Confidence

Freezing levels are uncertain on Monday

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.