When the sun pokes out natural slab and loose dry avalanche activity will likely increase.
Confidence
Moderate - Wind effect is extremely variable
Weather Forecast
Friday: A mix of sun and cloud with alpine temperatures near -9 and freezing levels dropping to valley bottom. Ridgetop winds light from the North.Saturday: Sunny. Alpine temperatures near -5 and freezing levels valley bottom. Light winds from the North.Sunday: A mix of sun and cloud. Alpine temperatures -7 and freezing levels rising to 800 m. Light winds from the northeast.
Avalanche Summary
On Thursday, avalanche control with explosives triggered numerous slab avalanches up to size 2. Cornice releases triggered wind slabs from the slopes below up to size 1.5. With colder temperatures expected this weekend, natural avalanche activity will likely taper off, but human triggering will be possible especially on leeward slopes and behind terrain features.
Snowpack Summary
Snow surfaces vary from aspect to elevation showing crusts, wind pressed and scoured conditions. In the alpine 5-15 cm of recent snow, accompanied by strong winds from the southeast have formed reactive wind slabs in leeward terrain and large looming cornices exist, they are fragile and demand respect. Treeline and below treeline elevations a melt-freeze crust has formed.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. Below this, the snowpack is thought to be generally strong and well-settled.
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.