Weather Summary 12/31/17 Image

The second week of advisories are in the books and boy was it a doozie.

The week started cold and relatively calm. Over the Christmas Holiday snow slowly started to accumulate as 3-6 inches of snow accumulated monday and again on Tuesday. Snows tapered slightly Wednesday before picking up thursday as another 5-10 had accumulated mid-week.

Friday marked the arrival of the pineapple express and the snow started in earnest, accompanied by an avalanche warning. Temperatures increased as the storm developed leading to an upside-down storm slab. Friday brought .9-2.4 inches of snow water equivalent. The storm continued on Saturday bringing an additional foot of snow with 1-2 inches of snow water and winds kicked up Saturday. Sunday brought an end to the avalanche warning but a high avalanche danger remains on wind loaded terrain.

The storm cycle brought a very interesting progression of avalanche problems. Before the storm cycle the greatest concern were the facets on the Thanksgiving crust. Once the facets were buried deep enough the concern shifted to the heavier warm storm snow falling on cold snow. The storm slab was very reactive and easily triggered across the region. The storm slab problem brought the facets back into play as step down avalanches became a very real possibility. During this time widespread natural and human triggered avalanches were reported throughout the region. Numerous large avalanches were reported and areas that rarely slide were also found to have had significant avalanche activity. As the storm dissipated and conditions slowly settle out wind slabs are becoming an increasing concern as winds increased late in the storm. With lots of snow available for transport and strong winds, wind slabs will be large and sensitive.

The first two storm cycles of the season have resulted in avalanche warnings and there have been a number of close calls already. As you celebrate the new year, consider your avalanche skills. Are you sure that you and your partners are ready to act if things go sour. Practice your rescue skills, talk through conditions with partners and keep a keen eye on conditions as they change, and as always ski and ride safe.

~Logan