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Avalanche Forecast

Archived

Mar 20th, 2022–Mar 21st, 2022

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

Regions

Sea To Sky.

Carefully assess the wind slab hazard as you move through terrain. New wind slabs could build through the day.

Confidence

Moderate - The snowpack structure is generally well understood.

Weather Forecast

Sunday night: 5 to 15 cm of new snow expected with strong southwest winds. Low of -2 at 1500 m.

Monday: cloudy with 5 to 10 cm of new snow expected. Moderate to strong southwest winds and freezing levels rising to 1500 m. 

Tuesday: cloudy with flurries bringing 5 cm of new snow with strong southwest winds. Freezing levels rising to 2000 m.

Wednesday: cloudy with around 5 cm of new snow expected. Strong southwest winds in the morning and light in the evening. Freezing level aaround 1900 m.

Avalanche Summary

On Saturday ski cutting and explosive control produced storm and wind slab avalanches up to size 1.5. These avalanches were generally in the immediate lee of ridge features at treeline and above. Several small cornice failures were also reported.

Snowpack Summary

Wind slabs can be found on north and east aspects at treeline and above. south facing slopes are pressed or scoured in the alpine. Moist snow could be observed at lower elevations.

30 to 90 cm overlies the mid March layer. This layer presents as surface hoar in shady, wind-sheltered areas and a hard melt-freeze crust on all aspects below 1700 m and on sun-exposed slopes into the alpine.  

Over one meter deep, a layer of facets may be found above a melt-freeze crust that formed in February. This layer had been most reactive on north and northeast aspects between 1600 and 2100 m. This layer is currently considered dormant. 

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Use ridges or ribs to avoid areas of wind loaded snow.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

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.

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.