A Special Public Avalanche Warning is in effect.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
On Sunday, expect 5-10 cm snow and moderate to strong SW winds. Snow eases to light amounts on Monday, then the next pulse begins on Monday night, bringing around 5-15 cm snow with moderate to strong SW winds. Freezing levels are between 1800 m and 2200 m, dropping on Tuesday to around 1600 m.
Avalanche Summary
A widespread avalanche cycle ran on Thursday and Friday in response to wet and windy conditions. These were a mix of storm slab, loose wet avalanches and persistent slabs, up to size 3. A few remotely triggered avalanches were also reported.
Snowpack Summary
Strong winds have shifted snow onto lee slopes at high elevations. Rain on Friday soaked the upper snowpack to at least treeline. Two persistent weak layers in the upper metre or so of the snowpack are the main story. They have been keeping conditions spicy. The mid-March layer, around 60 cm down, is most reactive where it exists as a crust. Around 80-100 cm down, the mid-February facet/crust interface has also been reactive with large loads like smaller avalanches stepping down, cornice fall or explosives. Both layers are sensitive to triggering and propagate easily, causing very large avalanches.
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.