Avalanche Forecast

Moderate - Forecast snowfall amounts are uncertain

Thursday: New snow 10-25 cm by early afternoon. Ridgetop winds strong from the southwest. Alpine temperatures near -5 with freezing levels 1600 m. Friday: Mix of sun and cloud with alpine temperatures near -10 and freezing levels at valley bottom. Ridgetop winds light from the north.Saturday: Mostly clear with no forecast snow. Alpine temperatures near -10 and ridgetop winds light from the northeast.

On Tuesday, a couple of natural wind slab avalanches up to size 2.5 from east aspects above 2000 m were reported. Avalanche control, using explosives also triggered numerous persistent slab avalanches up to size 2.5. These were mostly from N-SW aspects above 1900 m. One of these large avalanches stepped down to ground in some places on a early season November crust. With forecast snow and strong winds expect large natural avalanche activity to continue through the forecast period.

Up to 20 cm of new storm snow accompanied by strong winds adds stress to the upper snowpack. This now brings 90-140 cm of settled snow over two surface hoar/ crust layers that were formed early to mid-January. Digging deeper 160-200 cm sits the mid-December surface hoar layer. All of these persistent weak layers lurk within the snowpack and continue to be reactive, producing large and destructive avalanches. Near the base of the snowpack exists a crust/ facet interface which could be triggered by a step down avalanche, cornice failure, thin to thick spot triggering by people or reaching its threshold with new load from above. The snowpack is extremely complex and requires respect and diligence at this time.