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Avalanche Forecast

Archived

Jan 29th, 2016–Jan 30th, 2016

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

Regions

Purcells.

Patience and diligence may be required to resist venturing into complex terrain as the snowpack settles and adjusts to the recent load and warming.

Confidence

High

Weather Forecast

SATURDAY: A mix of sun and cloud with isolated light flurries. Freezing levels around 1200m and light southwesterly winds. SUNDAY: A mix of sun and cloud and mainly dry with freezing levels dropping below valley bottoms and light variable winds. MONDAY: A mix of sun and cloud with isolated light flurries. Freezing levels in valley bottoms and light southwesterly winds.

Avalanche Summary

Reports from Thursday include several natural and human triggered 50-60cm thick persistent slab avalanches up to Size 2 running on surface hoar buried at the beginning of January. Some were remotely triggered by as much as 30m away. Explosives control also produced relatively harmless loose wet and storm slab avalanches

Snowpack Summary

Weakness linger within and under the 30-60cm of rapidly settling recent storm snow with reports of moderate sudden results in snowpack tests. Southwesterly winds have continued to build fresh wind slabs on the leeward side of ridgecrests and behind terrain features on cross-loaded slopes. 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.