Avalanche Forecast

The sun has started to leave its mark on the snowpack this past week, triggering natural avalanches. Wind slabs found on southwest to southeast aspects were released and reached up to size 2.5. Most of these were in the alpine and some at treeline.

On Wednesday, there were several cornice failures throughout our region. It is suspected that they were weakened by the solar effect. Most of these were in the alpine and on the east to northeast aspects. Most of these cornices did not trigger the slope below them but they did reach sizes of 2.5. One cornice fall did trigger the deep persistent slab on the slope, northeast aspect, below and a large size 3 avalanche was the result. The layer that was triggered was 250 cm below the surface.

To the south of our region, the sun did not need the assistance of cornice failure to trigger the deep persistent layer. A large natural size 4 avalanche was reported in the south-central part of our region. Its failure plane was buried 140 cm below the surface.

Read more about managing the deep persistent slab problem in our latest Forecaster Blog.

In the alpine and at treeline wind slabs may be found on all aspects due to variable winds. These wind slabs are made of the 20 to 60 cm storm snow that arrived last week. In areas not affected by the wind, this recent snow overlies a weak layer of faceted snow and a sun crust on sun-affected slopes. Thursday's sun and warm temperatures will have likely developed a sun crust on steep solar aspects at most elevations. At lower elevations, warm daytime temperatures may have also created a melt-freeze crust.

The mid-snowpack is generally strong but the lower snowpack is a different story. The November facets are still prominent at the base of the snowpack. They are showing signs of rounding but there is still a considerable step in resistance between them and the overlying snow. These facets are most pronounced in shallow rocky areas.

Thursday Night

Clear with some clouds, no accumulation, winds easterly 15 to 25 km/h, freezing level dropping to the valley bottom.

Friday

Mostly cloudy, trace to 5 cm accumulation localized to the southern half of the region, winds easterly 20 km/h gusting to 40, treeline temperatures -8 °C with freezing levels climbing to 1200 m.

Saturday

A mix of sun and cloud, 2 to 10 cm accumulation mostly arriving in the early morning hours and for the southern parts of the region, winds east to southeast 15 to 25 km/h, treeline temperatures around -10 °C.

Sunday

A mix of sun and cloud, trace accumulation, winds south southeast 15 to 25 km/h, treeline temperatures -10 to -5 °C.

More details can be found in the Mountain Weather Forecast.

• Recent wind has varied in direction so watch for wind slabs on all aspects.
• Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
• Avalanche hazard may have improved, but be mindful that deep instabilities are still present.
• Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.