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Avalanche Forecast

Archived

Mar 16th, 2021–Mar 17th, 2021

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

Regions

Northwest Inland.

Southwesterly winds continue to form wind slabs on lee and cross-loaded terrain features in the alpine. Use caution when transitioning into wind affected terrain and avoid wind loaded slopes below ridgetops.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

  

TUESDAY NIGHT: Partly cloudy with isolated flurries; 0-5 cm. / Moderate, southwest ridgetop wind / alpine low temperature -8 / Freezing level 800 m.

WEDNESDAY: Mostly cloudy with isolated flurries; 0-5 cm. / Strong, southwest ridgetop wind / alpine high temperature -2 / Freezing level 1000 m.

THURSDAY: Mix of sun and cloud / Moderate, southwest ridgetop wind / alpine high temperature -1 / Freezing level 1200 m.

FRIDAY: Mostly cloudy with isolate flurries; 0-3 cm. / Strong, southwest ridgetop wind / alpine high temperature -3 / Freezing level 1000 m.

Avalanche Summary

No new natural avalanches and a few size 1 skier triggered wind slab avalanches in the alpine were reported on Monday.

A natural avalanche cycle with storm slab avalanches up to size 2.5 were reported in the southwest of the region throughout the weekend. 

Snowpack Summary

5-10 cm of new snow adds to the 15-20 cm of storm snow over the weekend, except for the southwest of the region where weekend storm totals range between 50 and 100 cm. Recent southerly winds are forming fresh wind slabs on lee features below alpine ridgetops. At lower elevations the precipitation fell as rain. 

The new snow overlies a variety of surfaces including hard wind affected snow at alpine elevations, weak, surface hoar crystals on northerly aspects and in sheltered terrain features around treeline, or a melt-freeze crust on southerly aspects and below treeline.

The mid and lower snowpack is reported as well settled and strong in most areas. However, weak facets exist at the base of the snowpack in the more shallow snowpack zones within much of the region and always have the potential of being triggered on steep, rocky slopes with a shallow or thin to thick snowpack; especially with large loads such as a cornice fall.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Avoid exposure to slopes that have cornices overhead.

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.