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Avalanche Forecast

Archived

Mar 23rd, 2020–Mar 24th, 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.

There is uncertainty in the forecast due to a lack of data available at this time.

Confidence

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

Weather Forecast

MONDAY NIGHT: Cloudy with isolated flurries, accumulation 2 to 5 cm, light northeast wind, alpine temperature -10 C.

TUESDAY: Morning clouds and afternoon clearing, moderate north wind, alpine temperature -12 C.

WEDNESDAY: Clear skies, moderate northwest wind, alpine temperature -6 C, freezing level 1000 m.

THURSDAY: Cloudy with snowfall accumulation 5 to 10 cm, moderate to strong west wind, alpine temperature -6 C, freezing level 800 m.

Avalanche Summary

No new avalanches were observed on Monday from limited reports. Looking forward, wind slab activity may increase as the wind speed increases and new slabs form.

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. These slabs will sit on a melt-freeze crust on sun-exposed slopes and otherwise previously wind-affected snow, so the new slabs may take some time to bond to the snowpack.

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.

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 outcrops. 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.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • 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.