Confidence
Fair - Intensity of incoming weather systems is uncertain on Thursday
Weather Forecast
Wednesday: Cloudy with scattered light flurries increasing to moderate snowfall overnight. Strong SW winds are expected with the onset of significant precipitation and freezing levels should hover around 900m. Thursday: Snow with 5-10cm of total accumulation. Strong SW winds and freezing levels around 1000m, but above freezing temperatures could extend as high as 1700m. Friday: Continued light to moderate snowfall, especially for the Cascades. Moderate NW winds and freezing levels dropping to 600m.
Avalanche Summary
No avalanches were reported on Monday.
Snowpack Summary
Snowpack depths vary greatly across the region with 165cm at treeline in the Cascades but only about 65cm in the Duffey Lake area. In general, the snowpack across the region is significantly thinner than average for this time of year. Terrain below treeline is still mostly below threshold for avalanche activity. Snowpack testing on a SSE facing slope at 2000m in the Duffey Lake area on Monday produced easy to moderate, sudden collapse compression test results, and a RB3, whole block release Rutschblock result down 20cm on the mid-December surface hoar, as well as moderate sudden planar and RB1 results down 46cm on the late-November facets where they were found above a hard crust. However, these weak interfaces appear generally well bonded in the Cascades.Early season riding hazards such as rocks, stumps and logs are lurking below the surface at treeline elevations and below.
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.