More snowfall followed by strong to extreme winds will continue to add complexity to an already weak and variable snowpack. It's a good time for conservative terrain use. JH
Weather Forecast
Sunday: A building ridge causes flurries to taper off, with some afternoon sun possible. -15, light winds.Monday: Return of the Westerlies! Expect: racing clouds, strong Westerly winds, blowing snow, and slightly rising temperatures (-11).Tuesday: Continued Zonal flow but with some embedded fronts: Strong Westerly winds, snowfall (5-10cm), and -9.
Snowpack Summary
New snowfall is burying a variable snowpack with several layers of wind slab (from extreme West winds) at all elevations. In deeper snowpack areas, hard persistent slabs (from earlier SW winds) sit on a faceted mid and lower snowpack. In thin snowpack areas, several layers of hard wind slab are sitting on weak, large, developing depth hoar.
Avalanche Summary
Explosives control work at neighboring avalanche operations has been producing large avalanches daily in wind exposed terrain, especially in areas that were shallow prior to recent wind loading from the west.Shooting cracks and whoomphing were observed in pockets of hard wind slab over depth hoar in Eastern (shallow snowpack) areas on Friday.
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.