Lots to think about: 1) New slabs have formed, which may not bond well to underlying snow surfaces. 2) The sun could trigger avalanches on solar slopes. 3) Expect large and touchy cornices on ridges. Conservative decision making is recommended!
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
FRIDAY NIGHT: Cloudy with snowfall, accumulation 10 to 15 cm, moderate to strong westerly winds, treeline temperature -3 C, freezing level 500 m.SATURDAY: Sunny with late afternoon clouds, light northwesterly winds, treeline temperature -4 C, freezing level 800 m.SUNDAY: Mostly cloudy with early-morning snowfall, accumulation 10-15 cm, strong westerly winds decreasing to light over the day, treeline temperature -3 C, freezing level 800 m.MONDAY: Mostly cloudy, light southwesterly winds, treeline temperature -3 C, freezing level 800 m.
Avalanche Summary
No new avalanches were reported on Thursday. On Tuesday and Wednesday, several natural wind slab avalanches were reported from all aspects up to size 2. Expect natural and human-triggered avalanche activity to increase with the storms and warming sunshine.
Snowpack Summary
Around 20 to 30 cm of storm snow fell with strong southwesterly winds, producing storm slabs on all aspects with deeper deposits found in lee features. This snow fell on previously wind-affected surfaces. The new snow may not bond well to these surfaces and could be reactive to both natural and human triggers.A hard rain crust that extends into alpine terrain is buried about 50 to 90 cm. Reports suggest the snow has a poor bond to the crust with test results showing sudden planar characteristics and a Rutschblock 2 (the whole block failing after standing on it). Monitor the bonds of the new snow as well as the bond of the snow directly above the buried crust. There are no substantial layers of concern below the crust.Also make note of cornices at ridgeline. Variable winds in the past month have produced cornices on all aspects. They will become touchier as they grow in size, as temperatures rise, and as the sun packs a strong punch on clear days. Stand well back of them!
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.
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.