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Avalanche Forecast

Archived

Mar 28th, 2020–Mar 30th, 2020

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

This forecast lacks field observations and has lots of uncertainty. This will be the last avalanche forecast of the season. Reactive wind slabs remain the primary concern, especially around ridge features and wind loaded terrain.

Confidence

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

Weather Forecast

Saturday night: Flurries, 5-10 cm. Alpine low temperature -8 C. Moderate to strong southwest wind.

Sunday: Flurries and snow, 5-15 cm. Alpine high temperature -7 C. Moderate southwest wind.

Monday: Cloudy with isolated flurries. Alpine high temperature -11 C. Moderate southeast wind.

Tuesday: Mix of sun and cloud. Alpine high temperature -13 C. Light east wind.

Avalanche Summary

No new avalanche observations were reported this week, this comes from a very limited observation network. 

Snowpack Summary

Around of 10-20 cm of snow has accumulated around the region over the past few days, along with a steady westerly wind. This covers a variety of wind-affected surfaces and a melt freeze crust on south aspects and slopes below 1100 m.

A weak layer of surface hoar crystals buried early March may be found around 30 to 50 cm deep, particularly in sheltered terrain around treeline. Recent observations of this layer are lacking.

An early-season layer of faceted grains and melt-freeze crust near the base of the snowpack likely lingers in high alpine features. The most suspect locations to trigger this layer would be where the snowpack is thin near rocky outcroppings. Large loads, such as cornice fall, may have the potential to trigger it.

Terrain and Travel

  • Watch for avalanche hazard to increase throughout the day.
  • Make conservative terrain choices and avoid overhead hazard.

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.

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.