January 1st – 6th: Major Storm Impacts the Area

By Arden Feldman            CBAC Intern

The New Year began with two low-pressure systems, one in the northwest, and another off the California/Baja coast creating a stream of moisture from the Pacific into Colorado. This produced 12-18” of low density snow across the area. CBMR reported 14” of snow and .3” SWE over the two days. Winds out of the southwest averaged 10-25 mph above tree line with gusts in the 50’s.

1/1/17 – Satellite image from the National Weather Service showing the two low-pressure systems, one in the northwest and another off the California/Baja coast. Clouds can also be seen beginning to form over Colorado.

 

The storm picked up in intensity from the night of January 3rd through the 5th. The jet stream lined up overhead producing a west-southwest flow and providing abundant moisture from the Pacific. By the morning of January 5th, Schofield had received 3.7” of SWE and 30” of snow since January 1st. On the 5th, a powerful cold front slowly sagged south over Colorado and the Crested Butte area got pummeled with snow falling at 2-3” per hour rates throughout the day. After the cold front passed, measured storm totals since New Year’s Day were 5.56” of SWE and 57” of snow at Irwin, 5” of SWE and 41” of settled snow at Schofield, and 47” of snow at CBMR. Behind the front, colder, drier air moved in, leaving clearing skies and frigid temperatures in its wake for January 6th.

1/4/17 – Satellite image from the National Weather Service showing the abundant moisture flowing into Colorado from the Pacific.

 

There were a number of problematic surfaces at the storm interface that had formed over the previous dry week, including near surface facets, surface hoar, melt-freeze crusts, and slick wind crusts. The storm created a sizeable slab that was sitting on those interfaces and persistent weak layers. The observed human triggered and natural avalanches grew larger in size as the storm progressed. Initially, there were touchy, relatively shallow storm slab instabilities, even with surprisingly low density and incohesive slabs. By the later parts of the storm, larger avalanches were failing naturally on these interfaces. The avalanche danger was rated as HIGH on both January 4th and 5th and a major natural avalanche cycle occurred with reports of many D2 to D3 avalanches around the zone. There was even some avalanche activity that 45-year locals had rarely seen.

1/3/17 – Skier triggered D2 storm slab on Schuylkill Ridge that failed on a surface hoar layer buried at the beginning of the storm.

 

1/6/17 – Natural D2.5 Persistent Slab avalanche on a southeast aspect of Purple Peak.

 

1/6/17 – Natural D2.5 persistent slab avalanche on an east aspect of Mt. Owen.

 

1/6/17 – CBAC Snodgrass Snow Study Plot profile showing the snowpack after this week’s major storm.