New wind slabs may form overnight with light snowfall and moderate SW winds.The persistent weak layer from early February is gaining strength but don't write it off yet, large destructive avalanches may still be possible.
Summary
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain on Saturday
Weather Forecast
A weak storm front is expected to reach the region Friday night. 5-10cm of snowfall is expected by midday Saturday. Alpine winds are expected to be moderate to strong from the southwest and freezing levels are forecast to be around 1700m. A weak ridge of high pressure should dry things out Saturday night. A mix of sun and cloud is expected for Sunday with light to moderate alpine winds from the southwest and freezing levels around 1600m. The second storm front is expected to arrive Sunday evening and another 5-10cm is forecast for the overnight period. Dry and mostly cloudy conditions are currently forecast for Monday.
Avalanche Summary
On Thursday, numerous natural loose avalanches up to size 2.5 were reported from steep sun exposed slopes. Explosives triggered a bunch of cornices up to size 2.5 and a couple natural cornices releases was also reported. Most of these cornices were on north aspects at treeline and in the alpine. Two cornice releases slabs on the slopes below. One was a 35cm thick wind slab on north aspect at 2600m and the other was 60cm thick slab on a north aspect at 2100m. Wind slabs were reported to be reactive to ski cutting in immediate leeward features in the far north of the region. On Wednesday, a natural size 3.5 slab avalanche was reported from an east aspect at 2700m which released down 100cm and was 250m wide. Three natural cornice releases size 1.5-2 were reported in the high alpine. Numerous size 1.5-2 natural loose avalanches were reported from south aspects in the alpine. Explosives triggered three slab avalanches on northern aspects which were 10-30cm thick. New winds slabs are expected to be the biggest concern on Saturday but deeper persistent layers may remain reactive in isolated areas.
Snowpack Summary
The new storm snow will bury a sun crust on south facing slopes and widespread surface hoar and/or facets everywhere else. New wind slabs are expected to form over the weekend with forecast moderate southwest winds in the alpine. The surface hoar and/or crust layer which was buried February 10 is now down 40-70cm and has been responsible for some large avalanches recently. This layer is expected to become much less reactive over the weekend with cooling temperatures. Large cornices have recently been a concern but should also gain strength will colder temperatures. The early January surface hoar/facet layer is typically down 70-120cm. Triggering an avalanche on this layer has become unlikely but it still has isolated potential to produce very large avalanches with a heavy trigger. In general, the lower snowpack is well settled and strong, apart from some thin snowpack areas where basal facets exist.
rbuhler,
Avalanche Canada
