Avalanche Forecast
Issued: Mar 12th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Cornices, Loose Wet and Wind Slabs.
JSmith,
Avalanche Canada
Things are looking HOT up high for the next couple days. Overhead hazards such as cornice failures and wet loose avalanches on large alpine slopes will be the primary concern. Pay attention to what's above your head and back off of slopes if the snow surface becomes moist.
Summary
Confidence
Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.
Weather Forecast
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FRIDAY NIGHT: Clear / Light, southwest ridgetop wind / alpine low temperature -11 / Freezing level valley bottom.
SATURDAY: Sunny / Light, southwest ridgetop wind / alpine high temperature 5 / Freezing level rapidly rising to 2500 m. and remaining elevated overnight.
SUNDAY: Sunny / Moderate, southwest ridgetop wind / alpine high temperature 5 / Freezing level 2300 m.
MONDAY: Mix of sun and cloud / Light, northeast ridgetop wind / alpine high temperature 2 / Freezing level 2000 m.
Avalanche Summary
On Thursday, there was report of a skier triggered size 2 storm slab avalanche on a southeast aspect in the alpine. The sun had warmed around 20 cm. of convective new snow just enough to react as a soft slab on a steep, convex feature.
The rapidly rising freezing level and sunny skies on Saturday are expected to elevate the avalanche hazard through the weekend.
Snowpack Summary
10-20 cm. of recent low density, convective snow is being warmed by sunny skies and forming soft slabs, especially in wind affected terrain in the alpine. The convective nature of spring storms results in widely varying snowfall amounts. Sunny skies are forming sun crusts on solar aspects which are breaking down during the heat of the day and increasing the likelihood for wet loose avalanches. Dry snow still exists on north aspects at upper elevations. Large cornices loom over alpine ridgetops.
Persistent weak layers of surface hoar, crusts, and/or facets 80-120 cm. down have recently been unreactive and no recent avalanches have been reported on these layers. However, big warm ups, like the one headed our way this weekend can awaken dormant weak layers resulting in large avalanches. Steep, rocky, convex terrain with a shallow or thin to thick snowpack are examples of places where triggering these layers are more likely.
Sunshine and warm temperatures often cause large cornice failures which are hazardous on their own and can also trigger large avalanches on deeper weak layers that the weight of a single rider would not trigger.
Terrain and Travel
- Avoid exposure to slopes that have cornices overhead.
- Cornice failure may trigger large avalanches.
- Back off slopes as the surface becomes moist or wet with rising temperatures.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
Problems
Cornices
Rapidly rising freezing levels and sunny skies significantly increase the likelihood of cornice failures which are hazardous on their own and can also trigger large avalanches on deeper weak layers that the weight of a single rider would not trigger. Avoid exposure to slopes that have cornices overhead.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Loose Wet
Naturally triggered wet loose avalanches are likely, especially on steep solar aspects in the alpine.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Recent convective flurries in parts of the region, solar radiation, and light to moderate winds may have formed reactive slabs in isolated alpine locations. Steep, convex slopes below alpine ridgetops are the most likely places to trigger these slabs.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Mar 13th, 2021 4:00PM
