Clear skies will bring strong solar heating but likely decent re-freezes Monday and Tuesday mornings. Start early and finish early. A poor recovery, calm winds and high freezing level are likely for Wednesday.
Weather Forecast
Midday clearing Sunday generated moist snow on south aspects despite the cool temperatures. This clearing marks the start of formation of a ridge of high pressure. Expect a 2000m freeze level Monday, 2500m Tuesday (with some significant winds), and 3300m Wednesday (little wind) with strong solar inputs. Models show a poor recovery Tuesday.
Snowpack Summary
5-10cm of snow with very strong SW winds on Saturday has formed new wind slabs above treeline. Buried temperature crusts exist to 2000m on all aspects and to ridge tops on solar slopes, including the Mar 15 sun crust down 40-70 cm in the alpine. Moist snow at lower elevations, with the entire snowpack becoming moist near valley bottom.
Avalanche Summary
Small soft windslabs were reactive to ski cutting today in isolated locations in the lee of alpine features. Forecasters observed a powder cloud sweep the E face of Fay around 13:00 and suspect a sz 2 cornice or windslab failure. Lots of loose wet avalanche activity on steep solar aspects in the past several days once the sun comes out.
Problems
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
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.