Avalanche danger ratings in the alpine on Sunday and Monday are HIGH where direct sunshine is affecting the slope. If it's cloudy, assume the danger is CONSIDERABLE.
Confidence
Fair - Timing or intensity of solar radiation is uncertain
Weather Forecast
Sunday: Locally variable light convective snow showers, amounting to a few cm. Sunny breaks in the afternoon. Generally light winds. Freezing level near 600m.Monday: Scattered cloud. Light winds. Cool in the morning and warming by afternoon with the influence of sunshine. Freezing level near 600m.Tuesday: Moderate snow and moderate to strong south-westerly winds. Freezing level between 500m and 1000m.
Avalanche Summary
Avalanches have been reported all week. On Friday, a number of natural and explosives-triggered storm snow avalanches in the size 1-2 range were reported, many on lee or cross-loaded north-east to north-westerly aspects. Reports of natural size 2-3, and numerous skier or explosives-triggered size 1-1.5 avalanches came in on Thursday on a variety of aspects. On Tuesday a natural avalanche cycle occurred up to size 3 on north to north-east aspects. Cornices reached their threshold and triggered slopes up to size 2.5 below. On Monday, a skier was partially buried and two others escaped a size 2 slab on an east aspect at 1500m, which failed on a crust. Natural and skier-remote triggered avalanches to size 3 were also observed on a variety of aspects and elevations, some failing on the mid-February weakness. Unsettled weather conditions continue. It may take several days for recent storm snow to settle out. If the sun shines through in your local mountains, expect strong solar radiation, snowpack deterioration, and elevated avalanche danger.
Snowpack Summary
In the past week 100-180 cm storm snow has fallen, accompanied by strong south-westerly winds. Storm slabs and wind slabs continue to build. Cornices are large, some reaching threshold and triggering the slopes below. The additional weight of new storm and wind slabs may step down and trigger a deep weakness, formed in mid-February. Recent test results on this layer produced hard sudden planar results. Very large avalanches are possible, which could be remote-triggered, triggered mid-slope, and/or propagate into low-angled terrain. The average snowpack depth at treeline is 350 cm.
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.