Avalanche Forecast

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

Wednesday night: Partly cloudy, light north winds, alpine temperatures dropping to -14 C.

Thursday: Mainly sunny, light north winds, alpine high temperatures near -12 C.

Friday: Mainly sunny, light north winds, alpine high temperatures near -14 C. 

Saturday: Increasing cloud, light variable winds, alpine high temperatures near -15 C.

Recent strong winds have formed wind slabs in lee features at upper elevations that may be possible to human trigger. Over the last few days, operators in neighboring Glacier National Park reported several large (size 2-2.5) wind slabs releasing naturally on a variety of aspects. Cornices may be reaching their breaking point and can act as triggers on slopes below. 

On Monday and Tuesday, several operators in the region reported small (size 1-1.5) human-triggered avalanches releasing on a weak layer of surface hoar on north, east and southeast aspects at treeline and below treeline elevations. These avalanches were breaking 25-45 cm deep. Check out this MIN report for a helpful example of a remote-triggered avalanche on this layer.

Recent strong winds built wind slabs in lee features at upper elevations over a variety of surfaces, including isolated surface hoar, sun crusts, and settling storm snow. Ongoing snow and wind over the past week have contributed to notable cornice growth. A new sun crust may be forming on steep solar aspects. 

50-70 cm of snow from the past week has buried a weak of layer of surface hoar that is likely to be preserved in sheltered, open slopes at and below treeline. Observers in the south of the region continue to report sudden results in the snowpack tests and shooting cracks on this layer. Don't let benign weather lure you into complacency. Recent avalanche activity demonstrates that this layer is likely to be reactive where it is preserved and that it warrants careful assessment. 

A couple of older persistent weak layers exist in the mid to lower snowpack. The distribution of these layers is variable, but they follow a similar pattern to the layer discussed above. The upper layer from late December, down about 70-120 cm, consists of spotty surface hoar at shaded treeline and below treeline elevations. The lower layer from early December buried 120-190 cm deep consists of a combination of decomposing surface hoar with a crust and faceted snow. Snowpack tests on these layers show increasingly unreactive results, suggesting a trend towards dormancy. 

• Carefully evaluate steep lines for wind slabs.
• Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
• Avoid exposure to slopes that have cornices overhead.