Confidence
Fair - Due to variable snowpack conditions
Weather Forecast
Sunday: Overcast skies / Light northeast winds / Freezing level at 1100mMonday: Mix of sun and clouds / Light east winds / Freezing level at 1100mTuesday: Mix of sun and cloud / Calm winds / Freezing level at 1400m
Avalanche Summary
In recent days, avalanche control has produced slab avalanches to size 2. They occurred on northeast facing slopes at 2600m and higher, and likely failed on the early April surface hoar. In general, observations have become very limited. I would expect new wind slab activity in response to new snow and wind on Friday night.
Snowpack Summary
Variable snowfall on Friday night has created new storm/wind slabs, especially near ridge top. This has added to existing storm slab and wind slab problems at alpine and treeline elevations. A surface hoar interface is buried within the upper metre of the snowpack, mainly on high-elevation northerly aspects. It is still producing moderate, sudden results in snowpack tests, and these slopes should be treated with suspicion. On other slopes, recent storm snow overlies a crust, with a variable bond. At low elevations, previously rain-soaked snow is likely to now be refrozen and strong.
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.