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

Regions

South Columbia.

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 25-30cm / Moderate to strong southwest wind / Alpine temperature -3 / Freezing level 1900mSUNDAY: Broken skies with isolated flurries / moderate west wind / Alpine temperature -11 / Freezing level 800mMore details can be found on the Mountain Weather Forecast.

Avalanche Summary

The past 2 days have seen a widespread natural avalanches to Size 4 at all elevations and on all aspects. Many of these triggered in the storm snow with some also stepping down to persistent weaknesses deeper in the snowpack and running full path. Wet slabs and loose wet avalanches have also been reported below treeline.

Snowpack Summary

Around 60-100cm of new snow has fallen at upper elevations over the past several days and has been redistributed by moderate to strong southerly wind. Warm temperatures on Sunday through Wednesday has resulted in moist and/or rain saturated snow on all aspects up to 2100m. There may now be a weak surface crust found between 1300 and 2100m. The snowpack below approximately 1300m is reported to be isothermic. The new snow sits on top of faceted snow as well as isolated small surface hoar in shelteredTue areas and a thin sun crust on steep southerly aspects. The persistent weakness buried late-February is now down 80-140 cm, and is composed of weak facetted crystals on a thick rain crust as high as about 1800m and facets on sun crust on steep southerly aspects. The mid and lower snowpack are well settled and stable in deeper snowpack areas, but may be weak and faceted in shallow areas.

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.