Fresh and reactive wind slabs formed in response to yesterday's wind event. Southerly aspects will likely be more reactive to human triggers especially at treeline and above. Old, buried wind slabs still linger on on aspects and elevations.
Summary
Confidence
Moderate - Forecast snowfall amounts are uncertain on Thursday
Weather Forecast
WEDNESDAY: Mix of sun and cloud. Alpine temperatures near -8 and ridgetop winds light from the East.THURSDAY: Cloudy skies with new snow 5-10 cm. Treeline temperatures near -6 and ridgetop winds light from the South. FRIDAY: Cloudy with scattered flurries. Treeline temperatures near -8. Ridgetop winds light from the southwest with strong gusts.
Avalanche Summary
On Tuesday, explosive controlled wind slab avalanches were reported up to size 2.5 failing on southerly aspects 1900-2100 m. Isolated wind slabs up to size 1 remain reactive to human triggers.Last Sunday, a large (size 2.5) persistent slab was triggered by a skier in the Evening Ridge area. It occurred on a southeast aspect at about 2000 metres and featured a crown fracture around 50 cm deep and 350 metres wide. A weak layer from early February is suspected as the failure plane. Human triggered avalanches were reported everyday between February 12 and 20. Although most avalanches were small (size 1-1.5), some had impressive propagation on buried weak layers (see some examples
here and
here). Last Tuesday, a notable size 3 persistent slab avalanche occurred on an east aspect at 2000 m. This avalanche was triggered by explosives and failed on the persistent weak layer that was buried on February 7th.
Snowpack Summary
Fresh and reactive wind slabs have formed in exposed terrain in response to yesterday's wind event. This
MIN report reflects the Kootenay Pass area well. The storm last weekend brought 15-25 cm of low density snow that now covers variable wind slabs at higher elevations and sun crusts on south-facing slopes. A weak layer of surface hoar (feathery crystals) and a crust that was buried on February 7th is now 30-50 cm deep. This layer has been reactive, and has produced avalanches as large as size 3. Two other surface hoar layers are buried 50 to 80 cm deep the snowpack (referred to as the February 1st and mid-January layers). Although they have not been reactive recently, they are still being monitored by professionals. The lower snowpack is considered generally strong.
swerner,
Avalanche Canada
