Snowfall amounts and timing of the approaching snowstorm are uncertain. If we receive much more than the expected 5 cm of snow then the strong southwest winds will likely create shallow wind slabs.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
FRIDAY NIGHT: Clear with cloudy periods / moderate west wind / alpine low -7 C / freezing level 800 mSATURDAY: Cloudy with a chance of sun / up to 5 cm of snow accumulation / strong southwest wind / alpine high -6 C / freezing level 1600 mSUNDAY: Cloudy / 10-15 cm snow accumulation / moderate west wind / alpine high -7 C / freezing level 1500 mMONDAY: Mix of sun and cloud / light southwest wind / alpine high -6 C / freezing level 1500 m
Avalanche Summary
On Thursday, a couple natural and machine triggered storm slab avalanches 20-40 cm deep and up to size 2.5 were observed on east facing alpine slopes.On Wednesday, no new avalanche activity was observed.On Tuesday, a small (size 1) slab avalanche 30 cm deep was remotely triggered by a skier from 80 m away on a northeast aspect at 2250 m. A layer of small surface hoar below the most recent snow may have been the weak layer. Additionally, several loose wet avalanches up to size 1.5 were triggered on solar aspects throughout the day by strong solar radiation.
Snowpack Summary
The new snow likely falls on a melt-freeze crust on all aspects except for north facing slopes above 2000 m, where the snow stayed dry. Last weeks unsettled weather produced 20-40 cm of snow which is slowly bonding on northern aspects where it might sit on surface hoar (weak, feathery crystals) in isolated locations. Older wind slabs sitting on surface hoar might still be sensitive to human triggers.Snowfall amounts taper quickly below treeline. Snow is disappearing rapidly at lower elevations.
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.