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
THURSDAY: Cloudy with isolated flurries bringing trace accumulations throughout the day with 3-5 cm overnight, light southwesterly winds, alpine temperature around -10.FRIDAY: Cloudy with isolated flurries bringing trace amounts of fresh snow, light southerly winds, alpine temperature around -10.SATURDAY: Cloudy with isolated flurries and trace amounts of fresh snow, light southeasterly winds, alpine temperature around -10.
Avalanche Summary
No new avalanches have been reported. Lingering wind slabs may remain reactive to human triggering on specific features, such as the immediately lee of ridges and sun-exposed slopes.
Snowpack Summary
Surface hoar is growing and the upper snowpack is faceting. 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. Continued moderate to strong northerly winds have been keeping wind slabs fresh and touchy in some areas and sun-exposure is likely making the wind slabs extra touchy on south-facing slopes. Facets and/or surface hoar buried mid-December recently gave moderate but broken snowpack test results where it was found down a metre or more. In a shallow snowpack area, recent snowpack tests gave moderate sudden collapse results on this persistent weakness. This suggests that the primary concern for persistent slab avalanches is in shallow snowpack areas; however, the potential for step-down avalanches remains where it is deeper. The lower snowpack is well bonded and features a thick rain crust near the ground.
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.