We should see a rapid increase in temperatures early this week, resulting in a spike in avalanche danger. Check out the latest forecasters blog for advice on how to manage these changing conditions.
Weather Forecast
Monday: A mix of sun and cloud. Freezing level is at valley bottom and alpine temperatures rise to -10. Winds are light from the north. Tuesday: Mainly sunny with possible valley cloud. An above freezing layer will develop between 1200-1500 m. Winds are light to moderate from the north. Wednesday: Much the same as Tuesday - continued warm alpine temperatures and generally clear skies.
Avalanche Summary
The upper snowpack has tightened up with the cold temperatures and the time elapsed since the last storm. Overall numbers of avalanche observations have decreased, but the avalanches are getting more interesting/scary. A group of skiers remotely triggered a size 2 avalanche from 70m away on a W facing aspect at TL Friday. Explosive work in the region didn't produce much activity Friday.
Snowpack Summary
40 - 90 cm of settled storm snow rests on the January 4th interface which consists of small facets, surface hoar (up to 12mm) in sheltered treeline and below treeline areas and sun crust on steep south and west facing slopes. The bonds at this interface are gaining strength but I still wouldn't bet the house on it. Recent tests on this interface show shears trending towards Resistant Planar. Professionals operating in the region are most concerned about slopes that have not yet avalanched. Wind slabs formed during the last storm are getting old and tired.The deep crust/facet combo from early November is till evident but it is inactive at this point.
Problems
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.
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.