A touchy storm slab sits on top of a sensitive surface hoar layer primed for human triggering. Time to be conservative in your trip plans! Make low angle, low consequence terrain choices!
Weather Forecast
Alpine high of -10C with light precipitation and moderate W'ly winds. Thursday through Friday looks like light snow, cool temperatures and shifting light to moderate winds first SE on Thursday and back to W on Friday.
Snowpack Summary
45cm of storm snow resides over the Jan 4 interface and the Dec 15 surface hoar (PWL) is down ~75cm. Monday through Tuesday was a tipping point of storm snow over weak layers. Snowpack tests show propagation potential and a high likelihood for skier triggering. The Dec 15th Surface Hoar layer is most reactive at tree line and below.
Avalanche Summary
Tuesday's avalanche control produced numerous size 3 slab avalanches with one size 4. Monday a skier was fully buried by a self triggered slide releasing on the Dec 15 layer. Also reported Monday were several skier controlled avalanches to size 1.5 reported from the backcountry and skier remotes from 10m away, failing on the Jan 4 layer.
Confidence
Due to the quality of field observations
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.