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Avalanche Forecast

Archived

Apr 9th, 2021–Apr 10th, 2021

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

Regions

South Coast.

Ease into terrain cautiously with an assessment mindset on Saturday and expect the reactivity of new snow to increase with elevation and wind effect. Be especially cautious around steep slopes being hit by the sun. This is where natural avalanches will be most likely. 

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

Friday night: Cloudy with continuing snowfall bringing new snow totals to 20-30 cm by morning. Strong west winds shifting northwest as snowfall eases.

Saturday: A mix of sun and cloud. Moderate northwest winds easing over the day. Alpine high temperatures around -5 with freezing levels to 1000 metres. 

Sunday: Sunny. Light variable winds. Alpine high temperature near -2 with freezing levels to 1300 metres, continuing to rise overnight.

Monday: Sunny. Light to moderate northeast winds. Alpine high temperatures around +1 with freezing levels to 1700 metres.

Avalanche Summary

Fresh storm slabs will be in place over much of the region's higher elevations on Saturday. The new snow will very likely be reactive to human triggers, especially where wind loading has occurred. Where it sees solar exposure it will likely also shed naturally from steep slopes in loose sluffs and potentially as more destructive storm slabs.

We haven't received many observations for the South Coast region in the past few days. If you get out, please consider sharing your observations to the Mountain Information Network to help us know what conditions are like.

Snowpack Summary

About 25 cm of new snow is expected to accumulate by Saturday morning, bringing this week's storm snow total to about 30-40 cm. Strong southwest winds are expected to accompany the new snow, likely forming fresh and reactive slabs in many areas. 

The recent storm snow sits on a crust on sun-exposed aspects, and on all aspects below about 1400 m. It likely fell on either wind slabs or soft snow on north aspects above 1400 m.

Cornices are large and looming along ridgelines. Their release is unpredictable, requiring a large berth if you're travelling above or below them.

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.
  • Choose conservative terrain and watch for clues of instability.
  • 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.

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.