A new storm slab is developing. Watch for continued loading from the forecast new snow and wind this week.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Flurries and periods of light snow overnight are expect to accumulate 5-10 cm by Tuesday morning combined with moderate Northwest winds and alpine temperatures around -10. Tuesday is forecast to be drier with only periods of flurries along the area of colder arctic air to the Northeast. Light precipitation is expected to continue on Wednesday with light to moderate Southwest winds ahead of the next storm. The storm should start on Thursday, and at this time it looks like we may get 15-20 cm in the first pulse of moisture and then continued precipitation into the weekend.
Avalanche Summary
No new avalanches reported on Sunday. I expect that the new storm snow may have been easy to trigger where it was overlying a crust and/or surface hoar that was buried on January 30th. The new storm snow is likely to settle into a soft slab over the next few days.
Snowpack Summary
Up to 35cm of new snow fell over the weekend. This new snow sits on a variety of old surfaces. A crust can be found below about 1900m in the north of the region and below 2200m in the south of the region. At higher elevations the new snow covers old wind slabs formed by moderate southwest winds. Several persistent week layers can be found deeper in the snowpack that may be capped by the overlying crust at lower elevations. The mid-January surface hoar is buried between 40 and 80cm down and remains a concern at treeline and above. The mid-December surface hoar layer is now 80 to 140cm below the surface and appears to be slowly gaining strength.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.