Spring Conditions. The ridge of HIGH pressure is breaking down, and a weak weather system is moving on-shore. Expect high freezing levels to continue to result in wet slab and loose wet avalanches.
Summary
Weather Forecast
High cloud developing overnight with light southerly winds and freezing levels down to 2000 metres. Light precipitation starting Thursday morning combined with light southwest winds and freezing levels rising up to 2500 metres. Cloudy on Friday with 5-10 cm of new snow above 2000 metres and light southwest winds. Continued overcast with light precipitation and light winds on Saturday.
Avalanche Summary
On Tuesday there was a size 3.0 wet slab avalanche down to the ground that was explosives triggered in the Duffey Lake area, the avalanche released on a northwest aspect at 2200 metres and ran to valley bottom. We have a MIN report from Monday of a close call with a size 2.5 wet slab avalanche on a northeast aspect in the alpine on Hour Peak on the McBride range traverse. A skier triggered the large avalanche that released down 30 cm on an old melt-freeze crust and propagated a fracture about 50 metres wide. Most commercial operations in the region have finished their season and data is becoming sparse.
Snowpack Summary
Cornices remain a concern, in part because of the potential to trigger wet slab avalanches that run to valley bottoms. Monitoring the overnight freeze of the snow surface is very important. If the snow surface does not freeze overnight or if the crust is only a few cm thick, the effect of daytime heating and solar radiation will weaken the snowpack much more quickly than it would if there is a well frozen thick crust. This is because the crust must first melt before the sun can weaken the snowpack. With the warmest weather this year forecast, layers in the mid snowpack and near the ground have the potential to wake up and become active. While isolated and unlikely, avalanches could be very large. Glide cracks are widespread, active, and best avoided. Low elevation and thin snowpack areas have become isothermal, meaning the snowpack is 0 degrees Celsius throughout. An isothermal snowpack is more prone to full depth wet slab avalanches during the heat of the day, especially on steep rocky faces.
Problems
Wet Slabs
Wets slab avalanches continue to be a concern due to high daytime freezing levels. Forecast cloud may decrease the likelihood once the freezing levels drop and new surface crusts form.
Travel early before the heat of the day, and avoid big slopes in the afternoon.>Avoid rocky, shallow or steep slopes during the heat of the day.>Avoid sun exposed slopes, especially where the snow is wet, weak, and mushy.>
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Wet
Loose wet avalanches may continue due to one more day of high daytime freezing levels. If it rains before the surface re-freezes, loose wet avalanches will be very likely.
Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Start and finish early before the surface crusts melt.>
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Apr 21st, 2016 2:00PM
