Forecast snow and strong winds is driving the avalanche danger. Be alert to changing conditions and increased hazard.
Confidence
Moderate - Forecast snowfall amounts are uncertain
Weather Forecast
Thursday: New snow up to 20 cm overnight Wednesday. Clearing by the afternoon. Ridgetop winds strong from the southwest. Alpine temperatures near -5 with freezing levels 1600 m. Friday: Mix of sun and cloud with alpine temperatures near -10 and freezing levels at valley bottom. Ridgetop winds light from the north. Saturday: Mostly clear with no forecast snow. Alpine temperatures near -10 and ridgetop winds light from the northeast.
Avalanche Summary
On Tuesday, cornice triggers using explosives produced numerous results up to size 2. Cornices remain fragile, give them a wide berth from above and below. Some loose wet avalanches up to size 1.5 were reported from steeper terrain features below 1700 m. Avalanche activity will likely increase on Thursday with forecast snow and strong winds.
Snowpack Summary
New snow up to 10 cm and consistently strong winds from the south east have formed reactive wind slabs in exposed leeward terrain. Below this is a variety of old snow surfaces including wind pressed, scoured or fresh, low density snow in the alpine. Treeline and below treeline a melt-freeze crust exists with moist snow below 1500 m.An average of 170 cm of settled snow now sits on the mid-January crust which generally shows signs of bonding to the overlying snow; however, it has the potential to "wake-up" with a large trigger such as a cornice fall. Cornices are large and fragile and demand respect. Below this, the snowpack is thought to be generally strong and well-settled.
Problems
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.