Wind slabs and persistent slabs are trending smaller and less likely to trigger, but conditions still demand assessment of suspect features in wind affected areas and around sheltered openings at lower elevations.
Summary
Confidence
Moderate -
Weather Forecast
Monday night: Clear Light to moderate southeast winds.Tuesday: Mainly sunny with cloud increasing over the day. Light southeast winds. Alpine high temperatures around -10.Wednesday: Mainly cloudy with isolated flurries and a trace of new snow, continuing overnight. Light east or southeast winds. Alpine high temperatures around -7.Thursday: Mainly cloudy with scattered flurries bringing up to 5 cm of new snow and new snow totals to a possible 10 cm. Flurries easing overnight. Light to moderate southwest winds. Alpine high temperatures around -10.
Avalanche Summary
Observations from the past couple of days included several storm slab releases to size 1.5 in an area of the southwest of the region that saw 25 cm of new snow from localized convective snowfall. Loose dry releases to size 1 were also observed, owing to the low density character of the new snow. Two 40-60 cm deep persistent slab avalanches were also observed on south and west aspects at around 2400 metres.On Wednesday, numerous natural wind slab avalanches up to size 2 and several human triggered size 1-1.5 releases were reported on primarily south aspects at treeline and above.
Here is a link to a video of an avalanche that occurred last week in the Purcells. Great footage that illustrates the current wind slab problem in the region.Reports of persistent slab avalanches are becoming less frequent, suggesting our January weak layers have evolved into a lower likelihood avalanche problem that still requires a measure of discipline to manage effectively.
Snowpack Summary
Up to 25 cm of recent snow exists in a few areas toward the southwest of the region, the product of spotty convective snowfall at the end of last week. This new snow likely overlies sun crust on sun-exposed aspects. Below any new snow, strong ridge-top winds (most recently from the northeast) have created wind slabs on all aspects at upper elevations. These wind slabs have shown prolonged reactivity because of the faceted (weak, sugary snow) they overlie.Lower down there are two layers of surface hoar (weak, feathery crystals) that were buried at the end of January and mid-January. These layers are around 30 to 80 cm deep and are most prominent at lower elevations - especially below treeline. The surface hoar may sit on a crust on south facing slopes in specific locations, which is a dangerous combination.The base of the snowpack is composed of weak and sugary faceted grains that sit on a crust. This weak layer has produced large and destructive avalanches that are sporadic in nature and difficult to predict. See the Forecasters' Blog
here for more information on this problem. Continued cold temperatures have been progressively weakening the basal snowpack.
cgarritty,
Avalanche Canada
