Avalanche Forecast

THURSDAY NIGHT: Light snowfall continues with up to 5 cm possible by morning. Moderate southwest winds. Freezing levels drop to 500 m overnight.

FRIDAY: Scattered flurries with partly cloudy skies. Moderate southwest winds. Freezing levels rise to 1500 m. Alpine high of +1.

SATURDAY: Scattered flurries with partly cloudy skies, 5 cm possible over the day. Moderate southwest winds. Freezing levels rise to 1600 m. Alpine high of +2.

SUNDAY: Another 5 cm possible overnight. Scattered flurries with partly cloudy skies. Moderate northwest winds. Freezing levels around 1400 m, alpine high of -3.

Reports from Wednesday continue to indicate a reactive and unstable snowpack. 

• Several natural avalanches up to size 2.5 were reported in wind loaded terrain features.
• Numerous human triggered avalanches to size 2.5 were reported occurring on the buried weak layer of surface hoar, facets and crust. Several of these were remotely triggered. Activity occurred on south facing slopes where the crust is most prominent, and also on north facing slopes were surface hoar was preserved.
• Afternoon sun produced wet avalanches on sun affected slopes up to size 2. 

On Tuesday, numerous natural and human triggered avalanches were reported on these same layers. A very large deep persistent avalanche was reported on Tuesday in the Selkirks south of Glacier National Park. This avalanche occurred on a south aspect in the alpine and the failure plane is unknown. 

A recent report from the Valkyr Range indicates uncertainty surrounding the persistent weak layers buried within the snowpack. 

40-60 cm of settling storm snow is being redistributed into wind loaded features at higher elevations. At lower elevations moist snow or a melt-freeze crust likely exists from recent rain and warm temperatures.

This new snow is sitting on various surfaces, including sun crusts on southerly slopes, facetted snow, and isolated pockets of surface hoar. The new snow is bonding poorly to this old surface, producing large avalanches within the last 3 days. 

The late February persistent weak layer combination of crust, facets and surface hoar is down 40-50 cm. Two additional persistent weak layers from late January and mid-February are down 80-120 cm. They both consist of surface hoar and/or melt-freeze crusts. These layers are most concerning during periods of new loading, strong solar radiation, or significant warming. 

• Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
• Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
• Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
• If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.