Weather Forecast
Sunday: A ridge of high pressure should maintain dry conditions and sunny skies. The freezing level is around 1600 m with mountaintop temperatures around -5. Winds are light from the northeast. Monday: The ridge should hold for one more day allowing for a mix of sun and cloud. The freezing level should be around to 1500 m. Winds increase to moderate from the west. Tuesday: A frontal system should move across the region bringing more cloud and a chance of flurries. The freezing level is around 1000 m. Winds are moderate from the southwest.
Avalanche Summary
There was one report of a size 1.5 slab avalanche from a steep south aspect in the alpine on Thursday that appeared to involve the recent storm snow. There were also a few size 1 loose snow avalanches were reported running out of steep terrain.
Snowpack Summary
Up to 15 cm of recent snowfall has been redistributed into dense or hard wind slabs at higher elevations from variable winds. Moist snow or a hard sun crust is likley on steep solar aspects depending on whether or not the sun is shining. The new storm snow overlies old wind slabs in exposed areas, settled storm snow or spotty surface hoar in more sheltered terrain, and a crust on previously sun-exposed slopes. A variable interface (surface hoar/facets/sun crust) was buried on Jan 23 and is down about 20-40cm. In most locations it now appears to be well bonded. The lower snowpack is generally well-settled. Cornices in the region are reported to be well developed and loom over heavily used slopes. These cornices deserve our respect, especially with clear skies and warming forecast for the weekend.
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.
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.