Regions
Banff Yoho Kootenay.
Another pulse of snow and continued moderate to strong winds for Thursday. We have tricky conditions at treeline and above, and users should be very conservative with terrain choices. SH
Weather Forecast
Another pulse of snow starting mid day Thursday will see 10-15cm of snow and continued strong westerly winds. A NW flow with decreased winds will start Friday AM. Drier conditions for Friday and Saturday. Alpine temperatures will be in the -12 to -15 C range and will cool off Saturday night.
Snowpack Summary
Strong winds and light snow accumulations have formed fresh wind slabs 20-40cm thick in alpine lees. These sit over previous slabs up to 60cm thick at treeline and above. These slabs all sit over the poorly bonded Dec.19 facets. The Nov crust is 30-80cm deep. While it is not currently producing avalanches, we expect it could with more snow load.
Avalanche Summary
Visibility and observations were limited today, but still some reports of whumpfing and cracking and small fresh wind slabs (size 1 to 1.5) being easily skier triggered by avalanche control at the ski hills.
Confidence
Due to the number and quality of field observations
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.