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November 15, 2006 7:30 am
Good morning, this is Evelyn Lees with the
Alta and Snowbird resorts will be closed to uphill traffic today due to avalanche control work.
Under mostly clear skies, temperatures have dropped into the teens this morning, with slightly cooler air pooled in some valley bottoms. The northwesterly winds have finally decreased, and are generally less than 10 mph, with speeds in the low 20s across the highest peaks. When the snow finally tapered off yesterday afternoon, the two day storm totals were fairly uniform throughout the range - 10 to 15 of dense, wind compacted snow.
Snowpack and Avalanche Conditions:
Yesterday, there were natural, skier and explosive triggered avalanches throughout upper Big and Little Cottonwood Canyons, all failing on faceted snow near the ground. An outstanding companion rescue effort saved the life of a skier in upper Silver Fork yesterday. After skiing West Bowl, the party was climbing back to the ridgeline on a more northerly facing slope, when the slope fractured. One skier was totally buried for about 10 minutes and unconscious when dug up, but his condition rapidly improved. Brett Kobernik has compiled a preliminary accident report, which is posted on the web.
There were also three large slides in Grizzly Gulch along the north facing Patsy Marley ridgeline. At least one was triggered remotely and was 1-2 deep and 400 wide. Some slides were long running yesterday, a few initiated on lower angle slopes, and many natural and explosive triggered slides were large, piling up 3 to 5 feet of debris. The activity was most widespread at the higher elevations, above about 10,000. There were reports of widespread cracking and collapsing.
There is a very distinct pattern to these slides: they are all above about 9,200, on the shady northwest through easterly facing slopes, and are failing on sugary, weak facets at or near the ground. This nasty weak layer formed on slopes where there was snow left from the early September and October storms. Many slopes in the backcountry did not slide naturally, and are just waiting for a trigger. While the snow may be a bit more stubborn today, it will still be possible to trigger one of these large slides to the ground. Stay off of and out from under these shady, upper elevation slopes.
The avalanche danger is CONSIDERABLE on northwest through easterly facing slopes above about 9,000, steeper than about 35 degrees. Large human triggered avalanches are possible, and can be triggered on the slope or remotely from a distance, so also avoid travel below steep slopes. At mid and low elevations and the on sunny slopes that had no preexisting snow prior to last weekends storm, the avalanche danger is LOW.
An upper ridge will bring warmer and drier weather today. Highs will be near 40 at 8,000 and in the upper 20s at 10,000. Winds will be from the northwest, generally in the 5 to 15 mph range, with averages 10 to 20 mph across the highest terrain. Increasing clouds tonight, with a weak cold front pushing into the area tomorrow, bringing a few inches of wet snow. Light precipitation is also possible on Friday and Saturday.
If there is anything we should know about, continue to let us know by calling (801) 524-5304 or 1-800-662-4140, email [email protected] or fax 801-524-6301
Finally, remember that this avalanche bulletin describes general conditions and that local variations always occur. Be sure to take a reputable avalanche class and learn to judge local conditions as you travel.