Avalanche Data:  

The initial release was 1’ deep, 35’ wide, and 20’ from crown face to stauchwall. As this pocket traveled down slope, it released the skier’s left flank and reached a maximum width of 120’. The average depth of the crown face was 1’, with pockets of up to 3’. As the avalanche descended, it gouged into old faceted snow and entrained much of the snow in the track. The avalanche ran 1,000’ vertically, classified as HS-AR-R3-D2-O. The deposition had tongues that were up to 10’ deep, averaged 5’.

Weather and Avalanche History:

Winter got off to a slow start in the Wasatch and unusually warm dry weather prevailed through the entire month of October. The first of November heralded a change in the pattern with a warm, wet system moving into the region on Nov. 2^nd. Moderate rain fell to the highest elevations, but colder air eventually filtered into the range. The nearby Alta Collins study plot reported 6” of snow with a whopping 1.6” of water. A colder system moved into the region on Nov. 4^th and 5^th ushering in a Wasatch-esque 47” of snow with 2.9” of water. Several smaller storms throughout the month followed bringing monthly water totals 7.76” and 74 inches of snow.  Of note- two separate and unusual rain/rime events occurred in November- one on Nov. 12 the other more significant event transpired on Nov. 28^th. The Thanksgiving crust was widespread throughout much of the Wasatch. Temperatures were relatively mild throughout the month.

A graupel storm kicked off December depositing 6” of dense snow with .80” water on the 2^nd. Two storms followed on the 3^rd and 4^th delivering a total of 6” snow with .40” water. Daytime high temperatures only reached into the low 20’s. 11” of snow with .50” water fell on Monday Dec. 8 followed by four days of daytime highs in the upper 20’s to low 30’s. Prefrontal south and southwest winds as recorded at the Mt. Baldy wind site close to the accident, increased late in the day on Friday Dec.12 with hourly averages in the teens, gusting into the low 40’s. Southwesterly winds continued through early Saturday morning, before switching to the northwest ushering in a cold front and 10” of snow with .50” water. West and northwest winds blew in the teens, gusting in the 30’s along the high ridges on Saturday Dec. 13^th.  Winds relaxed on the morning of the 14^th.

While the Election Day storm got things rolling, an extended period of high pressure followed for most of November creating a weak faceted snowpack. Early December storms were meager and the structural integrity of the snowpack deteriorated further. A pencil hand hardness slab formed by strong winds on the evening of December 12^th creating a strong feeling yet deceptively tricky snowpack. Several human triggered avalanches ensued in the backcountry over the next few days involving this weak interface.

Danger Rating:

The

Utah Avalanche Center

’s backcountry danger rating was posted as the upper end of Moderate.

The forecaster elaborated on the best chance of human triggered avalanches would be on west through north through southeast facing upper elevation slopes.