Regions
Banff Yoho Kootenay.
This is a good time to be conservative in your terrain choices and minimize exposure to avalanche terrain. The chances of human triggered avalanches will increase as temperatures rise.
Weather Forecast
A temperature inversion will continue through the forecast region, with alpine temperatures above freezing through Monday into Tuesday. Skies will remain relatively clear and winds in the light to moderate range. Expect unusually strong solar outputs for this time of the year on South and West aspects Monday and Tuesday afternoon.
Snowpack Summary
Warm alpine temperatures and clear skies moistening the upper snowpack on steep S-W aspects. There is 30-50 cm over the Dec.15 persistent weak layer of facets and surface hoar. This Dec 15th layer is becoming reactive to skiers at treeline and above and producing easy to moderate snowpack test results. Below this is a heavily faceted snowpack.
Avalanche Summary
The Dec 15 interface continues to show signs of reactivity, reports throughout the forecast region note significant whumphs and cracking from skier traffic at treeline and above. Avalanche activity from this problem was observed along the sunshine road releasing a size 2 slab.
Problems
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.
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.