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Avalanche Forecast

Archived

Mar 24th, 2020–Mar 25th, 2020

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

Regions

Northwest Inland.

Forecast confidence is low due to a lack of field observations. New and reactive wind slabs are expected to exist in higher elevation terrain.

Confidence

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

Weather Forecast

Tuesday night: Clear. Moderate north winds, increasing into the morning.

Wednesday: Sunny. Moderate to strong north winds shifting west. Alpine high temperatures around -7.

Thursday: Cloudy with scattered flurries bringing up to 5 cm of new snow, easing overnight. Moderate to strong southwest winds. Alpine high temperatures around -8.

Friday: Cloudy with isolated flurries and a trace of new snow, increasing overnight. Moderate to strong southwest winds. Alpine high temperatures around -9.

Avalanche Summary

No new avalanches were observed on Monday or Tuesday from limited reports. 

Looking forward, recently formed wind slabs may remain reactive to human triggering over the coming days.

Snowpack Summary

Around 5 to 15 cm of snow fell Sunday night with northeast wind. Wind slabs may form in areas where the wind speed picks up on Tuesday night. Any new slabs will sit on a melt-freeze crust on sun-exposed slopes and over previously wind-affected snow on other aspects. Slabs formed over crust may take a bit longer to stabilize.

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 limited.

An early-season layer of faceted grains and melt-freeze crust near the base of the snowpack may linger. The most suspect locations to trigger this layer would be where the snowpack is thin near rocky outcroppings. A large load, such as a cornice fall, also has the potential of triggering it.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
  • 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.