Warming temperatures and Solar radiation will play a leading role in the avalanche hazard in the coming days. Pay special attention to large mature cornices !
Confidence
Fair - Freezing levels are uncertain
Weather Forecast
Synopsis: A high pressure ridge will dominate the weather pattern for the next few days bringing warm temperatures and clear skies.Tonight: Clear with some cloudy periods, no precipitation, freezing level dropping to valley bottom. Ridge top winds light to moderate from the south west.Wednesday: Sunny with cloudy periods, no precipitation in the forecast, freezing level rising to 1800m. winds from the south west, light to moderate.Thursday: Cloudy periods, possibility of flurries, freezing level around 1500m. Light to moderate ridge top winds.Friday: Cloudy with isolated flurries, trace of precipitation, freezing level around 1600m, light, locally moderate south west ridge top winds.
Avalanche Summary
Large natural avalanches are still being reported throughout the forecast area. Explosives control has also produced some quite large results in some cases with wide propagations running full path over 1600 vertical metres. Cornice failures are beginning to show up on the reports, and yesterday a size 2.5 avalanche was triggered by snowboarders at 2600 metres on a south east aspect. Neighboring forecast regions have reported large avalanches initiating in the new storm snow, then stepping down to deeper layers, some running full path to the ground. .
Snowpack Summary
The recent snowfall in now developing into a dense slab. In some deeper snowpack areas 80 to 100cm of storm slab overlies a weak surface hoar layer that has been preserved in sheltered areas. A buried sun crust exists on solar aspects and and wind slabs have formed at tree line and above. On lee slopes these accumulations have been pushed into much deeper deposits by moderate to strong southwest winds. Warming has added cohesion to the slab and wider propagations are now being reported. With rising temps and solar radiation, moist snow surfaces have been reported into the alpine. Wet avalanches on solar aspects have also been reported. There is ongoing concern for a mix of weak surfaces which were buried on February 10th. This persistent interface lies between 60 and 160cm below the surface, and includes surface hoar, well developed facets and a mix of hard surfaces which remain widespread at all aspects and elevations. In many parts of the forecast area, large destructive avalanches are still a very real concern with ongoing reports of natural avalanches running full path. Weak basal facets exist in many areas, but without a large load, triggering now is unlikely.
Problems
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.
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.