Cautious travel practices, and conservative decision making is essential through the forecast period.
Confidence
Fair - Forecast snowfall amounts are uncertain on Wednesday
Weather Forecast
Wednesday: Cloudy with lingering snowfall. Expect 20-40cm of total accumulations, with the higher amounts in the southern portion of the region. Winds should be strong southwesterlies with freezing levels climbing to 1300m.Thursday: There is a chance of continued flurries, with westerly winds abating and temperatures falling to -13.Friday: Expect mixed skies with light winds and cool temperatures.
Avalanche Summary
Small windslabs up to size 1.5 have been reported, failing in immediate lee locations of ridgelines and isolated storm slabs have been reported to 1.0. Sluffing up to size 1.5 continues.
Snowpack Summary
On the west side of the region up to 50cm of new snow overlies the January 4th interface while on the east side the new snow totals around 10-20cm. Consistent moderate and strong south/southwest winds have redistributed this new snow into windslabs in lee features in the alpine and exposed treeline and these windslabs are reactive to human triggering. In some areas the windslabs extend lower down the slope than normal due to locally extreme winds.The January 4th interface consists predominantly of loose facets. In isolated locations (sheltered treeline and below treeline) surface hoar is present and there is a sun crust on steep south and west facing terrain. In some areas the new snow is bonding poorly to these interfaces, and lots of sluffing is being reported. Where the storm snow is deeper (around 30cm), the sluffing is extensive enough to require a management plan. The deepest deposits of storm snow (pushing 50cm) are settling into a more cohesive storm slab. The midpack is well bonded and strong. The deep crust/facet combo from early November still exists and concern remains (although unlikely) for triggering this layer from a shallow spot.
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.
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.
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.