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Avalanche Forecast

Archived

Mar 15th, 2017–Mar 16th, 2017

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

Regions

Purcells.

Continued precipitation Wednesday night into Thursday combined with moderate to strong southerly winds will continue to keep avalanche danger ratings elevated. A cautious approach is recommended in the coming days. Updated March 16 9:00am

Confidence

Moderate - Forecast snowfall amounts are uncertain on Thursday

Weather Forecast

THURSDAY: Cloudy with sunny breaks and scattered flurries through the day, accumulation 10cm overnight Wednesday into Thursday / Moderate southwest wind / Alpine temperature -7 / Freezing level: 1200mFRIDAY: Scattered clouds and flurries / Moderate south wind / Alpine temperature -6 / Freezing level 1200mSATURDAY: Flurries, accumulation 10-15cm / Moderate to strong southwest wind / Alpine temperature -2 / Freezing level 1600mMore details can be found on the Mountain Weather Forecast.

Avalanche Summary

It is expected that there was a widespread natural avalanche cycle on Wednesday. On Monday natural storm slabs to Size 2 were reported above 2400m on south and east aspects. On Sunday afternoon a rider-triggered Size 2.5 persistent slab avalanche was reported near Golden. Average slab depth was 50cm on a steep north facing aspect near 2300m. Additionally, several storm and persistent slab avalanches to Size 3 were also reported on Sunday - most activity was above 2300m on a variety of aspects.

Snowpack Summary

Around 60-90cm of new snow has fallen at upper elevations over the past several days and has been redistributed by light to moderate southerly wind. Warm temperatures on Sunday through Tuesday has resulted in moist and/or wet surface 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 70-120 cm, 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.