Avalanche Forecast
Issued: Mar 11th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
cgarritty,
Avalanche Canada
The snowpack in our region has become complex, with multiple avalanche problems and weak layers in play. Picking out which layer or layers you're managing on a given slope carries lots of uncertainty, so manage it with conservative terrain selection.
Summary
Confidence
Weather Forecast
Wednesday night: Clear periods. Light to moderate northwest winds.
Thursday: A mix of sun and cloud. Light northwest winds. Alpine high temperatures around -10.
Friday: Cloudy with flurries bringing about 5 cm of new snow, easing overnight. Moderate east winds increasing over the day. Alpine temperatures dropping to about -15.
Saturday: Mainly cloudy with isolated flurries and a further trace of low density new snow. New snow totals of 10-20 cm. Alpine high temperatures around -19.
Avalanche Summary
Numerous small avalanches were triggered naturally and with skier traffic during the peak of Tuesday's storm, with crown depths between 5-30 cm deep suggesting both wind redistribution and the potential for multiple storm slab failure planes in the upper snowpack.
Two large (size 2 and 2.5) persistent slab avalanches were triggered by a skier and intentionally with a large snow machine on Monday. Both ran on the February surface hoar layer described in our Snowpack Summary and occurred on north and northeast aspects around treeline and below.
Over the past two weeks, small to large (size 1 to 2) avalanches have released on this surface hoar layer. They have most often released between 1800 and 2300 m on northwest to east aspects. This trend is suspected to continue as this layer slowly gains strength.
Snowpack Summary
10-20 cm of new snow accumulated in the region during Tuesday's storm. The new snow buried a thin new weak layer of surface hoar on shaded aspects as well as new sun crusts on more sun-exposed slopes. Numerous storm slabs were observed failing at this interface on Tuesday.
The new snow adds to 10-15 cm of snow in the west of the region and 20 to 35 cm in the east of the region from the past weekend. In some cases, the interface below this older storm snow may act as a secondary failure plane in the upper snowpack.
Collectively, these recent snowfalls have been loading a layer of feathery surface hoar crystals from late February that is now found 50 to 80 cm deep. This layer is most commonly found in open trees (e.g. in this MIN) or sheltered terrain around the upper part of below treeline, treeline, and lower alpine elevations. Check out the latest forecaster blog that offers a deeper dive into these conditions.
The remainder of the snowpack is strong and well-settled.
Terrain and Travel
- Use careful route-finding and stick to moderate slope angles with low consequences.
- Avoid freshly wind loaded terrain features.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
Problems
Storm Slabs
Around 15 cm of new snow accumulated above an array of surface hoar and sun crust throughout the region during Tuesday's storm, with heightened natural and skier triggered avalanche activity observed as a result. Aside from forming a widespread new new storm slab problem and wind slabs in exposed areas, the new snow adds to the load overlying another active storm interface as well as that over a more deeply buried persistent weak layer.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
Around 30 to 60 cm of snow overlies a weak layer of surface hoar. This layer has been most problematic on northwest to northeast aspects between 1600 m and 2300 m, but it may exist on all aspects and at all elevations. Assess the layer prior to committing to avalanche terrain or adopt a conservative mindset to avoid the problem.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 12th, 2020 5:00PM
