South Rockies

A Special Public Avalanche Warning is in effect.

Poor - Due to the number of field observations

The current warm stormy flow is expected to be replaced by brutally cold arctic air by this weekend.Friday: 15-35mm precipitation. Temperatures start warm, with a freezing level near 2000 m, but rapid cooling is expected by late in the day. This may lead to snow to low levels, and deep dry new snow at upper elevations. Strong to gale SW winds, easing as the cold air/snow arrives.Saturday: Any remaining flurries should fade out by afternoon. Becoming cold and clear. Light winds.Sunday: Cold and clear. Light winds. Brrr.

Explosives triggered a large (size 2.5) slab in the south of the region on Thursday around treeline. This failed on a weak layer of facets buried about a week ago. In the north of the region, numerous shallow size 1.5 slabs failed below treeline. Over in the neighboring Lizard/Flathead region, natural and human-triggered avalanches to size 2 have been reported. These either failed on basal facets or at the interface below the recent storm snow.

As we begin our forecasting season, we are working with very limited field data. If you have been out in the mountains, we'd love to hear from you. Please email us at [email protected], windy and warm conditions are likely to have created touchy slabs at alpine and treeline elevations. I suspect that recent storm snow overlies a weak old snowpack in many areas. South of the Crowsnest, skiers observed whumpfs and shooting cracks at alpine and treeline elevations on aspects sheltered from the wind. The weak layer was identified as facets above a crust which formed during the long dry spell earlier this month. The base of the snowpack here was very hard refrozen snow. As we look ahead to the sudden drop in temperature forecast for the weekend, be aware that snowpacks (especially those with known weak layers) don't like sudden changes. I'd treat the snowpack with a very wary eye until it has had time to adjust, especially at the highest elevations.