Avalanche Forecast

Moderate - Uncertainty is due to the limited number of field observations.

Wednesday night: Diminishing flurries bringing 5-10 cm of new snow. Moderate southwest winds, easing.

Thursday: Mainly sunny. Light west winds. Treeline temperatures cooling from -3 to -7 over the day.

Friday: Initially clear, clouding over by afternoon. Light northeast winds. Treeline high temperatures around -7.

Saturday: Cloudy with lingering flurries from the overnight period bringing 5-10 cm of new snow. Light to moderate southwest winds, easing over the day. Treeline high temperatures around -7.

A natural storm slab avalanche cycle occurred over Tuesday night. Details are still limited but it's safe to assume numerous large or even very large avalanches occurred during this period.

Looking forward, alpine areas where dry snow accumulated during the storm will remain a real concern for Thursday. Cooling temperatures should aid in stabilizing the snowpack but the alpine may need more time to adjust to the significant load of new snow.

The warm, wet storm from early in the week brought 50+mm of precipitation to the region. Above about 2100 metres, this fell as snow (up to 50 cm) under the influence of extreme southwest winds. At these upper alpine elevations, the new snow added to 20-50 cm of previous storm snow. A breakable crust (from Nov 27) exists about halfway through its depth. 

The new and older storm snow collectively overlies a mix of surface hoar, decomposing grains and faceted snow resting on a melt freeze crust from mid-November. Surprising large avalanches sliding on these weak layers were reported during the last storm. 

Below the storm's snow line, a rain-wetted 50 cm of older storm snow overlies the same crust. Areas where wet snow exists at or very near the surface will quickly stabilize as temperatures cool Wednesday night.

Average snow depths at treeline are now likely closer to 150-200 cm; 250+ cm in the alpine. Snowpack depths decrease dramatically below treeline and may still be below threshold for avalanches in some areas.

• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• Watch for areas of hard wind slab on alpine features.
• Avoid shallow, rocky areas where the snowpack transitions from thick to thin.