Tricky conditions persist in the alpine with fresh wind slabs and the continuing possibility of avalanches releasing on deep weak layers. Conservative terrain selection remains critical.
Summary
Confidence
Moderate -
Weather Forecast
On Friday, 5-10 cm of new snow is expected with moderate to strong alpine wind from the southwest and freezing levels reaching around 1600 m in the afternoon. Another 4-8 cm is expected on Saturday with light to moderate alpine wind from the southwest, freezing levels around 1600 m in the afternoon, and the potential for sunny breaks. Mainly dry and sunny conditions are forecast for Sunday with light alpine wind and afternoon freezing levels around 1700 m.
Avalanche Summary
On Wednesday, a natural size 4 deep persistent slab was reported but the date of the avalanche is uncertain. This failed on a broad ridge feature on south through north aspects, was 200 cm thick, and 1000 m wide. A natural size 2.5 storm slab was also observed on a northeast aspect at 2400 m and a natural cornice failed on west aspect at 2300 m which was solar triggered. Explosives triggered several slabs, a couple of which released down 200 cm. On Tuesday, explosives triggered two size 3 persistent slabs on west and north aspects at 2600-2800 m which failed down 100 cm. On Monday, a natural size 3.5 deep persistent slab was observed on a northeast aspect at 3300 m which released down 100 cm. Over the weekend, a widespread avalanche cycle occurred with avalanches up to size 4. This included avalanches releasing on layers near the ground, propagations over 1 km wide, and avalanches breaking trees.
Click here for photos of the recent avalanches. On Friday, wind slabs and cornice are expected to be reactive at higher elevations. We are in a low probability, high consequence scenario for persistent slab avalanches failing on buried weak layers.
Click here for more details.Snowpack Summary
Melt-freeze conditions are being reported below 2100-2200 m elevation with widespread crust being reported on Thursday. Recent strong wind from a variety of directions has formed wind slabs on all aspects in exposed terrain in the high alpine. Large cornices are also expected on northerly aspects in the alpine. At lower elevations, there are a couple rain crusts in the upper snowpack. The February crust/facet layer is now down around 90-150 cm and has been reactive with several avalanches recently releasing on it. It is expected to be most reactive in the alpine where the snowpack remains dry. The deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack and a few avalanches and cornice falls have stepped down to these layers recently resulting in very large avalanches.
rbuhler,
Avalanche Canada
