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Avalanche Forecast

Archived

Mar 29th, 2021–Mar 30th, 2021

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, 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

South Coast Inland.

 

Storm slabs at higher elevations may be reactive on Tuesday, especially in wind-loaded areas.

If the sun pokes through the clouds it can quickly initiate natural avalanches and weaken cornices. 

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

A ridge of high pressure will dominate for the next couple of days bringing cooler and dryer conditions. The Duffy will see stronger ridgetop wind than the Southern part of the region.

Tuesday: Mix of sun and cloud. Ridgetop wind moderate from the northwest. Alpine temperatures near -2 and freezing levels 1200 m.

Wednesday/ Thursday: Mix of sun and cloud. Ridgetop wind generally light with strong gusty periods from the southwest. Alpine temperatures near +1 and freezing levels 1800 m. 

Avalanche Summary

A widespread natural avalanche cycle occurred on Sunday afternoon and evening up to size 2.5 during the storm. A near miss was also reported on the Coquihalla size 2.5. Check out this MIN report for more details.  

A report from Mt. Rohr on Saturday showed a fresh cornice-triggered slab from a steep piece of terrain, a great reminder of cornice and associated avalanche hazards.

Looking forward, new snow from Sunday's storm may need a day or so to settle and form a good bond with the old surface. Extra caution should be taken in wind loaded areas, which may begin to include more south slopes as a forecast shift to north winds takes place.

 

Snowpack Summary

40-60 cm of new snow blanketed the region by Monday morning. This snow fell with strong southwest wind building fresh reactive storm and wind slabs. The new snow has buried a mix of widespread hard crust and a bit of moist new snow below about 1700 metres and to either sheltered low density or wind-affected dry snow above this elevation. The lower snowpack is strong and settled.

Cornices along ridgelines are large and looming, especially after this storm. Avoid slopes with cornices overhead and give them a large berth while travelling along ridgelines. 

Terrain and Travel

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

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.

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.