Deja Vu for Saturday - new snow is blown around, creating Wind Slabs lee to strong South-West winds. Sunday sees an Upslope switch, with new snow being reverse loaded by North-East winds. Watch for Wind Slabs on both sides of ridges Sunday onward.
Weather Forecast
Saturday: Increasing cloud cover, with Strong Westerly winds easing late afternoon . Temperatures steady around -10.Sunday: Overnight switch to cold North-East winds (Strong in the Alpine, Moderate at Treeline) brings heavy snowfall in the early hours, tapering through the day. -20 at treeline.Monday: Frigid, Moderate North-East winds, flurries.
Snowpack Summary
New snowfall will form Wind Slabs lee to Strong SW winds on Friday night, then again lee to NE winds during Sunday. These cover hard Persistent Slabs, over facets in the middle and bottom of the snowpack. The distribution and sensitivity of these varies greatly, even across each slope. The snowpack is weakest in shallow and/or wind exposed areas.
Avalanche Summary
On Tuesday/Weds, shooting cracks and whoomphing were observed Below Treeline. One large avalanche noted from an Alpine lee slope.On Friday, several small Storm Slab and Wind Slab avalanches were observed in new storm snow, primarily on North and East aspects, at Treeline and Alpine elevations.Natural activity is possible on lee slopes Sat-Sun.
Confidence
Forecast snowfall amounts are uncertain on Sunday
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.