Persistent weaknesses deeper in snowpack still can't be totally trusted. Approach big open slopes with caution, especially in shallow snowpack areas.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
SATURDAY: Cloudy with isolated flurries and trace amounts of fresh snow, light southeasterly winds, alpine temperature around -10.SUNDAY: Mainly cloudy with light flurries, light becoming moderate southwesterly winds and alpine temperatures around -15.MONDAY: Mainly cloudy with light snow bringing up to 10 cm, alpine temperatures dropping to -20 and light to moderate southwesterly alpine wind.
Avalanche Summary
Reports from the Allen Creek area near Valemount include five recent rider-triggered persistent slab avalanches up to Size 1.5. All activity has been on northerly aspects with convex start zone above 35 degrees. Check out the MIN report for more details.
Snowpack Summary
Surface hoar and surface facets may buried by up to 15 cm of fresh snow in some places. In exposed areas at all elevations, recent winds have resulted in scouring, hard wind slabs, and thicker reactive wind slabs in unusual places as the winds shifted from west to northeast. Moderate southeasterly winds are likely keeping winds slabs fresh in some areas, while old wind slabs are breaking down with faceting in other areas. Persistent and deep persistent weakness in the mid and lower snowpack are giving variable results in snowpack tests, but are generally most touchy in shallow snowpack areas. Recent snowpack tests gave moderate but resistant results on facets and/or surface hoar buried mid-December where it was found down 45 cm, and hard but sudden collapse results on the facet/crust weakness down 116 cm near the base of the snowpack.
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.