Warming and solar radiation will drive the Avalanche Danger over the next few days. Use extra caution if solar radiation is strong on Monday.
Confidence
Moderate - Timing or intensity of solar radiation is uncertain on Monday
Weather Forecast
On Monday expect overcast skies in the morning with gradual clearing in the afternoon. Tuesday should be mainly clear with increased cloud forecast for Wednesday.. Ridgetop winds should remain mainly light from the southwest. Freezing levels will climb to about 3500m for Monday and Tuesday, and then drop to about 2200m by Wednesday.
Avalanche Summary
In the wake of Friday's storm, natural storm slab activity was noted throughout the region to size 3. Storm slabs have become much more difficult to trigger, but may still be sensitive to light inputs in high elevation lee terrain. Looking further ahead, rising freezing levels and solar radiation on Monday should spark a round of loose wet avalanche activity on sun-exposed slopes. Warming will also increase the likelihood of triggering cornice falls, wet slabs and deep and destructive persistent slabs.
Snowpack Summary
On Friday between 60 and 100cm of new snow fell. Strong to extreme southwest winds shifted these accumulations into deep and dense storm slabs. Cornices were already large before the storm, and new growth is expected to be fragile. About 70-100cm below the surface, you likely find a rain crust which formed on January 28th. This crust is widespread and exists up to about 2050m. Where it still exists, the mid-January surface hoar layer may be found between 130 and 200 cm below the surface. The combination of ongoing heavy storm loading and warm temperatures has flushed out this weak layer in most areas. That said, warming and solar radiation forecast for the next few days may be what it takes to wake up this deep and destructive persistent weak layer.
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.
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.