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Avalanche Forecast

Archived

Mar 16th, 2021–Mar 17th, 2021

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

Regions

Cariboos.

Spring-like diurnal conditions exist and it allows travel in avalanche terrain to be favorable at this time. Pay attention to steep south facing slopes as they heat up in the afternoon and destabilize. Give looming cornices a wide berth from above and below. 

Confidence

Moderate - Uncertainty is due to the limited number of field observations. Confidence is due to a stable weather pattern with little change expected.

Weather Forecast

A ridge of high pressure will remain anchored over the Interior until Thursday bringing warmer temperatures and sunny skies. 

The typical spring-like diurnal weather pattern will hold afternoon alpine temperatures near -2 and freezing levels around 1500-2000 m. Overnight periods will see the freezing levels drop back to the valley bottom.

An approaching Pacific frontal system will move onto the coast Wednesday bringing unsettled weather and new snow to the Interior regions by Friday and through the weekend. 

Avalanche Summary

No additional avalanche observations reported on Monday. I suspect daytime warming combined with solar radiation may pack enough punch to trigger loose wet avalanches, especially on sunny aspects. Large looming cornices may also become weak and fragile with warming. 

Snowpack Summary

5-15 cm of recent new snow and moderate southwesterly winds have formed fresh wind slabs below alpine ridgetops. Dry snow can be found on north aspects and crusty snow surfaces exist on solar aspects. Large cornices loom over alpine ridges and become weak with afternoon warming.

A persistent weak layer made up of surface hoar at treeline elevations and a crust with facets in the alpine on solar aspects can be found down 50-150 cm in some parts of the region. Only one recent avalanche has been reported on a deeper layer and this involved a very heavy trigger (a cornice).

Terrain and Travel

  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
  • A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

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.

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.