Continued elevated danger of skier and rider triggered avalanches today. It is time for very conservative route selection.
Weather Forecast
Cloudy with sunny periods and an alpine high of -10C today. Scattered flurries with a slowly rising freezing level and warming trend into the weekend. Potential for another 10cm of snow by Saturday. This additional load and warming will keep the snowpack weak layers touchy.
Snowpack Summary
We have three buried surface hoar layers two of which are touchy and sensitive to human triggering. Jan 4th surface hoar is down ~45cm and the Dec 15 surface hoar Persistent Weak Layer down ~100cm are ripe and ready to slide. Snowpack tests show propagation potential with sudden planar results on the Jan 4 and Dec15 layers.
Avalanche Summary
Several reports of skier triggered slides occurred yesterday. A size 2 slide at the top of Grizzly Shoulder, East aspect and 30 degree slope was 80m wide, 40cm deep and ran 80m down slope. A remote triggered size 1.5 slide at 1750m 1m deep, 25m wide and ran for 150m taking out part of the ski track. Several slides to size 2.5 in hwy corridor.
Confidence
Timing, track, or intensity of incoming weather system is uncertain
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.