Remotely triggered avalanche from the peak 300' wide on the east side caught and carried and partially buried two skiers.

Advisory from December 20, 2002

Avalanche Conditions:

Again yesterday there were plenty of avalanches, both from control work and human triggered. The layer these slides are releasing on is called faceted snow. It was formed during the long dry spell and produces notoriously long lasting and persistent instabilities. As we go into the weekend, don’t expect the backcountry conditions to get safer and indeed, with today’s wind and new snow, we will bump right back up to HIGH danger in some areas. There were many reports of widespread cracking and collapsing in the backcountry yesterday plus quite a few remotely triggered slides and a couple of people caught but not completely buried or hurt. A party on the north side of the ridge above Pole Line Pass between Big and Little Cottonwood remotely triggered a slide that ran over a couple of guys on the opposite side of the ridge.

The one saving grace to our situation is that many slopes avalanched naturally during the storm but, as usual, there are a couple of catches. First of all, it is often hard to tell for sure if a slope did slide if additional new or wind blown snow has covered the evidence. Secondly, many of the slopes that did run during the storm only partially released, leaving lots of snow still hanging in the balance. The east facing slope above Pole Line Pass that caught two skiers fits this pattern. Part of the slope had been released by highway control work the previous day.

Another tip is that southerly facing slopes have had little or no avalanche activity because areas that were largely bare a week ago don’t have the underlying weak layers. The catch here is that this window is fairly narrow with plenty of activity on west, east and even southeast facing slopes. The best defense at this time is carefully watching slope angles, staying down close to or below 30 degrees steepness. The catch to this caveat is that slides are being triggered remotely so if there is a steeper slope above you, you could easily trigger it from below. Also, slopes triggered remotely may take out adjacent lower angle terrain.

There have been plenty of slides on shady, mid and lower elevation slopes, where the weak facets were well preserved in wind sheltered areas. These slides are generally smaller in width, but still 1-2 feet deep, and large enough to get a person in trouble, especially if the snow piles up in a terrain trap such as a gully bottom or road cut. In all areas, collapsing and cracking are clues to the instability.

I am getting reports indicating that this morning’s winds are getting down into mid and lower elevation terrain as well as along the high peaks and ridges. With literally tons of light snow lying around, these winds will quickly increase the avalanche danger on all wind affected steep slopes.