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Avalanche Forecast

Archived

Feb 21st, 2023–Feb 22nd, 2023

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

Regions

Glacier.

Over a metre of new snow, winds from every direction, and now an Arctic deep freeze; cautiously approach the backcountry, given all the recent changes that Mother Nature has thrown onto the slopes!

Confidence

Moderate

Avalanche Summary

A natural cycle Tues AM, with the dramatic change in wind direction, saw numerous avalanches to sz 3-3.5, especially from S'ly aspects. This came after 2 consecutive days of artillery control, which produced good results to sz 4.

Skiers up Connaught reported all Cheops N paths (1 through 6) had run at least once today, along with Frequent Flyer in the AM.

Snowpack Summary

Roughly 1m of snow has fallen in the last 3 days, accompanied by strong SW winds, creating a widespread reactive storm slab. Winds have now flipped to the NE and reverse loading is stacking wind slabs on S'ly aspects.

Several thin crusts are buried below the storm snow on steep solar aspects.

The deep persistent weakness at the base of the snowpack has been showing signs of strengthening recently.

Weather Summary

Here comes the Arctic air mass! Cold, heavy air is pushing south, bringing frigid temps and gusty NE'ly outflow winds until Saturday.

Tonight: cloudy, nil snow, Alp low -28*C, moderate E winds

Wed/Thurs: sun and cloud, Alp high -25*C, light/mod E winds

Terrain and Travel Advice

  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
  • Avoid exposure to slopes that have cornices overhead.
  • Avoid freshly wind loaded terrain features.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.