A cooling temperature trend will improve snowpack stability. Depending on timing, south aspects in the alpine may still be affected by warm air and sunny skies. Watch for a moist snow surface, which is an indicator of a weakening snowpack.
Confidence
Moderate - Freezing levels are uncertain on Tuesday
Weather Forecast
MONDAY NIGHT: Mostly clear skies, light to moderate west winds, inversion conditions with above-freezing layer between 1900 m and 2300 m.TUESDAY: Mostly clear skies with valley clouds, light winds from southwest, alpine temperature up to 1 C, inversion conditions with above-freezing layer between 2300 m and 2500 m decreasing by the end of the day.WEDNESDAY: Increasing cloudiness, moderate southwest winds, alpine temperature around -5 C, freezing level below valley bottom.THURSDAY: Cloudy with sunny periods and isolated flurries, moderate winds from southeast, alpine temperature -8 C, freezing level below valley bottom.
Avalanche Summary
Numerous wet loose avalanches were triggered naturally on Sunday due to daytime warming and solar input. They were all large (size 2) released on steep south aspects.A few wind slab and storm slab avalanches were triggered naturally on Sunday. They were large (size 2 to 3), mostly on north and south aspects, and generally at treeline and alpine elevations.Finally, there was a large deep persistent slab avalanche (size 3-3.5) that was triggered with explosive on a southeast aspect in the alpine.
Snowpack Summary
On south aspects, warm air temperatures and sunny skies will continue to impact the snow surface at higher elevations where you will likely find moist snow during the day or a sun crust if it freezes. Wind slabs may still linger in lee and cross-loaded terrain features in alpine and exposed treeline terrain.The middle and lower portions of the snowpack are generally well-settled and strong. However, there still remain a few deeper weaknesses in the snowpack around treeline and alpine elevations. Professionals are still tracking a layer around 150 to 200 cm deep, composed of sugary faceted grains, feathery surface hoar, and a sun crust. The base of the snowpack may also still be composed of weak faceted grains. These layers would most likely be triggered by humans in areas where the snowpack is shallow.
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.
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.