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Avalanche Forecast

Archived

Mar 31st, 2021–Apr 1st, 2021

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

Regions

South Coast.

Rising temperatures coupled with spring sun can pack a punch and quickly initiate natural avalanche activity and weaken cornices. Be ready to back off slopes as the surface becomes moist.

Pockets of wind slab may linger on northeasterly facing alpine slopes

Confidence

Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

Wednesday Night: Cloud with alpine temperatures near +2. Ridgetop wind light from the South and freezing levels 1400 m. 

Thursday: A mix of sun and cloud with alpine temperatures near +2. Ridgetop wind light from the South and freezing levels 1300 m. 

Friday: Cloudy. Ridgetop wind light from the southwest. Alpine temperatures -1 and freezing levels 800 m.

Saturday: Precipitation amounts 10-20 mm with moderate ridgetop wind from the South. Freezing level 1200 m. 

Avalanche Summary

No new avalanches were reported by Wednesday afternoon. 

Pockets of reactive wind slab may linger on leeward slopes in the alpine. Melt-freeze snow conditions exist on most other aspects and elevations. Daytime warming may break down the crust and destabilize the upper snowpack. Back off slopes when surfaces become moist and punchy. Cornices are weak and unpredictable.

This MIN Report shows an extensive avalanche cycle in the alpine from last weekend. 

 

Snowpack Summary

Warm temperatures to the mountain top combined with the strong spring sun on Wednesday made most snow surfaces moist, except on the true North facing alpine slopes. With some overnight cooling, a melt-freeze crust may form on most aspects and elevations. Isolated pockets of wind slab may linger in the alpine just below ridgelines. 

The average snowpack depth at treeline elevations is 350 cm. The snowpack below treeline is significantly shallower and isothermal.

Along ridgelines, cornices are large and looming. They are very unpredictable and require a large berth if you're travelling above and below. 

Terrain and Travel

  • Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
  • Brief periods of sun could quickly initiate natural avalanche activity.
  • Be aware of highly variable recent wind loading patterns.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.

Problems

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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.

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.