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Avalanche Forecast

Archived

Mar 16th, 2017–Mar 17th, 2017

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

Regions

Purcells.

A momentary reprieve from the precipitation and high freezing levels on Friday. Yet we still have dangerous avalanche conditions. Saturday it will start all over with precipitation and warm temperatures forecast again.

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Saturday

Weather Forecast

FRIDAY: Scattered flurries / Moderate south wind / Alpine temperature -6 / Freezing level 1400mSATURDAY: Snow, accumulation 25-35cm / Moderate to strong southwest wind / Alpine temperature -3 / Freezing level 1900mSUNDAY: Broken skies with isolated flurries / moderate west wind / Alpine temperature -13 / Freezing level 800mMore details can be found on the Mountain Weather Forecast.

Avalanche Summary

The past few days warm and wet weather have seen a natural avalanche cycle to size 2.5 from a variety of aspects and elevations. In the coming days expect the likelihood of triggering an avalanche to remain elevated.

Snowpack Summary

Around 60-90cm of new snow has fallen at upper elevations over the past several days and has been redistributed by moderate southerly wind. Warm temperatures on Sunday through Tuesday has resulted in moist and/or rain saturated snow on all aspects up to 2100m. The new snow sits on top of faceted snow as well as isolated small surface hoar in sheltered areas and a thin sun crust on steep southerly aspects. The persistent weakness buried late-February is now down 90-140cm, and is composed of weak facetted crystals on a thick rain crust as high as about 2000m and facets on sun crust on steep southerly aspects. This layer has produced easy results in recent snowpack tests and has proven especially reactive on steep southerly aspects. Several deeper persistent weaknesses also remain a concern, including surface hoar buried early-February and mid-January (primarily in the northern Purcells). The november crust and basal facets are still reactive in shallow, rocky start zones.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.