The heat is on! If you're hoping to get one more alpine mission in, you need to get out super early Saturday and plan to be out of avalanche terrain no later than lunch time. Watch for the odd small wind slab in the alpine Saturday morning.
Weather Forecast
A significant pattern change is expected to commence Saturday as a strong ridge begins to build. After Friday night, temperatures are expected to remain well above freezing at all elevations for the foreseeable future. SATURDAY: Scattered cloud cover, freezing level beginning around 2000 m, climbing to 2500 m in the afternoon, no significant precipitation, very light southwest wind. SUNDAY: Clear skies, freezing level beginning around 2500 m, climbing to around 3000 m in the afternoon, no significant precipitation, light variable wind. MONDAY: Mostly clear skies, freezing level holding around 3000 m all day, no significant precipitation, light variable wind.
Avalanche Summary
No new avalanches have been reported in this region in the last week, but if you're out in the mountains you'll see lots of old loose wet and wet slab avalanche activity from the last big warm up.
Snowpack Summary
Cornices are large, fragile, and could trigger deep slab avalanches that run to valley bottoms. Monitoring the overnight freeze of the snow surface is very important during the spring. 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. Deeply buried weak layers in the mid snowpack and near the ground still have the potential to wake up and become active with a rapid warm up. While unlikely, releases on these deeply buried weak layers would result in very large avalanches. 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.
Problems
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
Wet Slabs
Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.