Avalanche Forecast

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

WEDNESDAY NIGHT: Cloudy, up to 10 cm new snow in the north and up to 20 cm in the southwest of the region, precipitation will fall as rain at lower elevations and the lower alpine, strong to extreme southwest wind, alpine temperature +1 C, freezing level 2100 m.

THURSDAY: Mostly cloudy with sunny periods, up to 2 cm new snow, strong to extreme west wind, alpine temperature -4 C, freezing level dropping slowly to 1400 m.  

FRIDAY: Mix of sun and cloud, trace of new snow, light to moderate westerly wind, alpine temperature -5 C, freezing level 1300 m.

SATURDAY: Mix of sun and cloud, moderate to strong west wind, alpine temperature -1 C, freezing level 1700 m.

On Tuesday, no new avalanches were reported. 

On Monday, a small skier triggered wind slab avalanche was reported and several slab avalanches released naturally on the buried weak layer. Wet loose avalanches were observed below 1000 m. 

On Sunday, a deep persistent slab avalanche was likely triggered naturally by intense warming and sun and released on depth hoar or the November crust. It occurred just south of the region (see this MIN report). Explosives triggered several large wind slab avalanches up to size 3.

The forecast precipitation Wednesday to Thursday night will fall as rain at lower elevations and the lower alpine and as snow at higher elevations. The snow surface will be moist or wet at lower elevations and likely form a crust when temperatures slowly drop during the day on Thursday. Previous storms brought 50 to 80 cm new snow with the highest amounts in the southwest, less in the north and the least in the east of the divide. The snow formed storm slabs in sheltered areas and wind slabs in lee terrain features from strong south and west wind.

The snow will be particularly touchy where it sits on a weak layer of surface hoar crystals. Reports suggest that the surface hoar is likely most prominent in sheltered openings at and below treeline but could extend into wind-sheltered terrain in the alpine. Example terrain features to treat as suspect include the lee side of protected ridges, openings in the trees, cut blocks, and burns.

The lower snowpack is generally strong and well-bonded. The base of the snowpack is expected to be weak and faceted in shallow, rocky slopes east of the divide.

• Rain or periods of intense solar radiation can rapidly enhance the effects of warming.
• Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
• Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
• Uncertainty is best managed through conservative terrain choices at this time.