Recent new snow combined with wind has promoted wind slab development as well as cornice growth. As the clouds part in the coming days remember that the sun packs a punch this time of year.
Confidence
Moderate - Timing or intensity of solar radiation is uncertain
Weather Forecast
TUESDAY: Mix of sun, cloud and isolated flurries / Light to moderate west wind / Alpine temperature -13WEDNESDAY: Mix of sun, cloud and isolated flurries / Light southwest wind / Alpine temperature -12 THURSDAY: Mix of sun and cloud / Light to moderate southwest wind / Alpine temperature -9
Avalanche Summary
There was a report from the western portion of the region of a natural size 3.5 deep persistent avalanche approximately 200cm deep on a west aspect starting in the alpine at 2300m running down to 1400m. This was reported on Saturday and occurred in the previous 24-36 hours.
Snowpack Summary
Recent storm snow is settling and has been redistributed into slabs in wind-exposed terrain. Below this is a layer buried mid-February that presents as a sun crust on solar aspects, and spotty surface hoar on sheltered slopes. This layer looks most concerning on on solar aspects where it's associated with with small facets or surface hoar above.There are several deeper layers in the mid-pack that have shown signs of improving but remain on the radar as a low probability to trigger, yet would produce a high consequence avalanche if triggered. We are talking about surface hoar buried back in December and January. Near the base of the snowpack is a November crust combined with loose sugary snow. These layers may "wake-up" with strong inputs such as sustained warming, sustained snowfall, large triggers (e.g. cornice fall, smaller avalanches coming down from above); human triggering is also possible in shallow snowpack areas with variable snow depth and convoluted terrain.
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.