Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
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 are quite high and as temperatures increase we will start to see more natural activity as well.
Weather Forecast
The winds will decrease on Sunday afternoon and the gradual warming continues as the high pressure system arrives. On Monday and Tuesday we expect an inversion to build with alpine temperatures forecast to be just above freezing. Valley bottom temperatures will remain at or below freezing. No significant precipitation is expected.
Snowpack Summary
Moderate to strong W winds and warming temperatures are forming wind slabs in the alpine. 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 sudden collapse results. Below this is a heavily faceted snowpack.
Avalanche Summary
Several small skier triggered slabs on the Dec 15 interface were reported on Saturday in the Rock Isle Lake area. A few small wind slabs from ski cutting and explosive work were seen at the local ski hills. Sluffing was observed in the alpine due to strong West winds. Lots of reports of whumphing and cracking in open glades at treeline and above.
Confidence
Due to the number of field observations
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.