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Avalanche Forecast

Archived

Mar 7th, 2020–Mar 8th, 2020

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

Regions

South Coast.

Slabs that formed from Thursday's storm may take a bit more time to bond to previous surfaces. Should the clouds clear, sun-exposed slopes could rapidly weaken and looming cornices could fail.

Confidence

High - Confidence is due to a stable weather pattern with little change expected.

Weather Forecast

SATURDAY NIGHT: Partly cloudy, light southwest wind, treeline temperature -5 C, freezing level 500 m.

SUNDAY: Mix of sun and cloud, light northwest wind, treeline temperature -5 C, freezing level 600 m.

MONDAY: Clear skies, light northwest wind, treeline temperature -4 C, freezing level 800 m.

TUESDAY: Cloudy with snowfall, accumulation 5 cm, moderate southwest wind, treeline temperature -2 C, freezing level 900 m.

Avalanche Summary

Many small storm slab and loose avalanches were triggered naturally and by skiers on Friday. This occurred within the storm snow that fell on Thursday.

Avalanche activity is expected to decrease as the storm snow bonds to underlying surfaces. Naturally avalanche activity is unlikely, unless the sun comes out and rapidly warms up the snow. Human-triggered avalanches remain possible within the storm snow and potentially the surface hoar layer described n the Snowpack Summary. 

Snowpack Summary

Thursday's storm dropped around 20 to 30 cm of snow across the region. The snow has consolidated into a slab that reportedly did not bond well to underlying surfaces. This snow is likely slowly gaining strength. The snow fell with strong south to southwest wind, which formed wind slabs in lee terrain features.

Around 100 cm of snow overlies a layer of surface hoar on north-facing aspects near and above treeline. Although there have not been and reported avalanches on this layer, it has been found to be reactive in some snowpack tests. This persistent weak layer warrants investigation and a conservative terrain-use strategy until it is clear that it is no longer a problem. Check out the latest forecaster blog that offers a deeper dive into these conditions.

The remainder of the snowpack is well-settled. The snowpack depth varies from around 300 to 400 cm around 1200 to 1400 m and tapering rapidly with elevation, with no snow below 700 m.

Terrain and Travel

  • The new snow may require another day to settle and stabilize.
  • Be careful as you transition into wind affected terrain.
  • Minimize your exposure time below cornices.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.
  • Surface hoar distribution is highly variable. Avoid generalizing your observations.

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.