It's a tricky time right now. Loose dry, cornices, wind slabs and persistent slab avalanche problems all exist. Keep the eyes open and the brain tuned in.
Weather Forecast
Flurries will start tonight and give about 4cm . Alpine temps will be -9 with 45km/hr winds. Tomorrow the flurries will continue and drop another 10cm. Overall winds will drop to 15km/hr but gusts will continue to reach 45km/hr. Alpine temps will hit -7C.
Avalanche Summary
Several older(early this week) slabs were noted. Many were thin alpine windslabs, cornice triggered and averaged size 2. East aspects were also a theme.
Snowpack Summary
A flight through the region today gave us a good look around. Most alpine areas have widespread wind slabs of various densities, but the tighter, sheltered drainages are still holding decent snow below ridgeline. Treeline has less wind affect overall with soft snow on sheltered north aspects. The aspect begins to play a role at this elevation. The Mar 15 crust is widespread on any solar aspect. It is down 20-40cm and so far has a decent bond to the surface layers. Intense sun today will likely form another thin surface crust on south aspects. Overall, the snowpack is reasonably solid, but still a ways from our usual spring like snowpack typical of late march.
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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.