A natural, heat induced cycle is just around the corner. Conditions will change very quickly with the warm weather forecast and current snow conditions. Even light loads, solar pin wheeling for example, may be a trigger for a large avalanche.
Weather Forecast
The warm weather is here. Today saw a major swing in the air temperature and considerable solar effect. We can expect the same for tomorrow and Sunday. We are at the time of year when things change extremely fast. Our forecasts for tomorrow are saying temps of around zero on the Spray Rd and just below zero in the alpine. The thin cloud will amplify the solar effect tomorrow. The alpine winds will continue in the strong range for most of forecast area. As for snow, we will see some flurries, but no significant accumulations. For Sunday, we are expecting another pulse of snow. Up to 20cm's.
Avalanche Summary
The clear skies today revealed a number of avalanches that had released during the storm. It appeared the failure layer was within the storm snow. All observed avalanches were in the alpine and ranged from N-E-S aspects. Of more importance today was the very touchy Feb 10th layer. Forecasters worked their way up a treed ridge and remotely released 2 large avalanches from 30m and 100m away. The specifics are: 2 avalanches, both Sz2, skier remote(30 & 100m), NE-E aspect, 35-45 degrees, the terrain was crossloaded and upper treeline. The furthest avalanche was triggered from the opposite side of the ridge. Both slides ran to mid path. Other observations today included another natural size 2 on an E aspect that originated out a variable depth alpine feature. Again, the Feb 10th layer is taking the blame.
Snowpack Summary
A few cm's of new snow overnight. The main story today was the drastic settling of the upper snowpack. The temperature rose dramatically today with an almost immediate settling of the snowpack. Up to 2300m the upper 10cm is now moist snow. All aspects have this problem to a certain extent. Obviously moist snow on the south aspects is more pronounced. In the alpine there was still some transport helping to build the current windslabs. The Feb 10th layer is down a meter in lee areas at treeline, and very reactive. Lots of whumphing and cracking in the PM. On south aspects, there is an old sun crust that is at the base of the storm snow, down 20-30. This may become a problem as it continues to warm.
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.
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.