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Avalanche Forecast

Archived

Jan 28th, 2016–Jan 29th, 2016

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

Regions

Purcells.

Continued conservative decision making is recommended as the snowpack settles and adjusts to the recent load and warming.

Confidence

High

Weather Forecast

FRIDAY: A mix on sun and cloud with isolated light flurries possible. Freezing levels dropping to 1200m and light southwesterly winds. SATURDAY: A mix of sun and cloud but mainly dry. Freezing levels dropping to 1000m and light northwesterly winds. SUNDAY: A mix of sun and cloud and mainly dry with freezing levels dropping below valley bottoms and light northwesterly winds.

Avalanche Summary

Reports from Wednesday include several natural wind slab avalanches up to Size 2 predominately on north through east aspects and on cross-loaded features in steep aline terrain. On Thursday, explosives control produced relatively harmless loose wet and storm slab avalanches as well as 30-50cm deep persistent slab avalanches up to Size 1.5 running on surface hoar buried early January.

Snowpack Summary

Most areas are reporting 10-25 cm deep fresh wind slabs that were loaded from moderate to strong southwest winds. Weakness linger within and under the 30-60cm of recent storm snow with reports of moderate sudden results in snowpack tests. The persistent weak layer of surface hoar buried early-January is now typically down 40-70 cm and appears to be quite touchy in some parts of the region. In general, the lower snowpack is well settled and strong.

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.