Temperatures are a huge factor in the snowpack stability these days. Traveling in the colder part of the day is essential. The large avalanche reported yesterday (see forecast details for more) is a sign of how much the sun can weaken the snowpack.
Weather Forecast
Light snow for the next 3 days. Amounts are expected to be minimal due to the rapid settlement and warm temperatures. Moderate winds at 3000m and light winds at valley bottom. The temperatures will rise throughout the next 36hrs with almost no overnight cooling.
Avalanche Summary
No new avalanches were noted today. A report came into the office today of a very large, surprising avalanche from one of our neighboring areas. The report said it was a remotely triggered, sz3.5 avalanche on a steep south facing, alpine slope. The failure plain was on ground.
Snowpack Summary
In alpine areas, almost 20cm's of new snow has fallen in the last 24hrs. The northern areas of the forecast region have seen the most accumulation with elevation playing a large role in snow depth. The winds have been low enough to limit the wind transport in the alpine. The sun on the other hand has enough strength to get through the thick cloud. By 1200hrs south aspects were softening at all elevations. The underlying surface tend to be crusts in various forms. Northern aspects have a frozen crust as a midpack, while the southern areas have a softer, partially frozen midpack. By 1300hrs today, the snowpack was still supportive.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.