Regions
Banff Yoho Kootenay.
Avalanche control on the Sunshine Road on Tuesday, no climbing or skiing in the slide paths tomorrow. Strong wind and snowfall overnight Monday will start a major avalanche cycle on Tuesday. Avoid avalanche terrain.
Weather Forecast
Warm temps, substantial snowfall and strong SW wind are forecasted Monday night and through Tuesday. This will initiate a major avalanche cycle. A slight cooling trend and easing snowfall is expected Wednesday.
Snowpack Summary
Recent storms have deposited 35-65cm of storm snow in the last 5 days. Increasing wind and steady snowfall today are loading 3 persistent weak layers of surface hoar and facets in the upper half of the snowpack: Jan 16 down 25-45cm; Jan 6 down 35-55cm; and Dec15 down 45-80cm. In snowpits, these layers are giving sudden test results.
Avalanche Summary
A skier remote avalanche (size 2) was reported in the Sunshine backcountry. Although visibility was limited there have been many reports throughout the forecast region of audible avalanches through the day as the storm intensifies.
Confidence
Timing, track, or intensity of incoming weather system is uncertain on Tuesday
Problems
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.