A cooling trend is helping to lower avalanche danger but has also brought a return to more wintery problems at higher elevations. New snow, sustained winds, and persistent weak layers mean that there are lots of factors to keep in mind to stay safe.
Weather Forecast
Thursday and Friday should be mostly dry but we may see a few flurries. Expect a mix of sun and cloud, alpine temps around -10, and moderate westerly winds. A weak storm is expected to arrive later on Friday, bringing increasing cloud and flurries. 9cm of snow are expected on Sat with freezing levels to 1500m.
Snowpack Summary
Temps have cooled off. At 1300m, a skiff of snow overlies a 3cm thick crust which should stay intact today. Above 1800m over 30cm of dry snow overlies a crust. 30cm of wet snow is buried and insulated down 60-100cm. Snowpack tests indicate that these layers may be triggerable by light loads, and if triggered are capable of propagating widely.
Avalanche Summary
No new natural avalanches were observed in Glacier National Park yesterday. Ski cuts produced small sluffs in the new snow on steep slopes at treeline. Wind slabs on lee features in the alpine were reported to be reactive to skier traffic, producing size 1 avalanches.
Confidence
Freezing levels are uncertain
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.
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.