Avalanche Forecast

Archived

Apr 1st, 2015–Apr 2nd, 2015

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Northwest Inland.

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Confidence

Good

Weather Forecast

Snow starting Thursday afternoon is expected to bring 2-5 cm by Friday morning and 5-10 cm throughout the day Friday into Saturday morning, before generally dry conditions prevail for Saturday. Generally moderate alpine winds are expected to shift between southeasterlies and southwesterlies throughout the forecast period. Daytime high freezing levels should hover around 1200 m each day as well.

Avalanche Summary

Reports from Tuesday include several small natural and skier triggered wind slab avalanches in lee and cross-loaded treeline and alpine terrain. The reports mentioned surprisingly little large avalanche activity given the strong winds and amount of fresh snow available for wind-transport.

Snowpack Summary

Approximately 15-30 cm of dense storm snow overlies a variety of crusty old surfaces. Recent strong winds have scoured windward slopes and loaded leeward slopes below ridgecrests and behind terrain features. Persistent weaknesses buried in the upper snowpack may include hard crusts and/or facet crystals, although not much is known about the reactivity or spatial distribution of these layers. At the base of the snowpack, weak facets may be found. Cornices are large and potentially fragile. Unpredictable, full-depth glide avalanches are also a concern on low elevation slopes with smooth ground cover (grassy slopes, rock slabs, etc.) where large cracks have formed from the snowpack slipping on the ground.

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.