Wasatch Cache National Forest

In partnership with: The Friends of the Utah Avalanche Center, Utah Department of Public Safety Division of Comprehensive Emergency Management,

Salt Lake County, and Utah State Parks:

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Avalanche ADVISORY

Thursday, December 09, 2004 7:30 Am

Good morning, this is Evelyn Lees with the Forest Service Utah Avalanche Center with your backcountry avalanche and mountain weather advisory. Today is Thursday, December 09, 2004, and it’s 7:30 am.

An Avalanche Warning remains in effect for the northern Utah mountains and extreme southeast Idaho through Friday morning. Heavy snow, strong winds and warming temperatures have created a High to Extreme avalanche danger. Avalanches are occurring at unusually low elevations in addition to the more typical mid and upper elevations. Both natural and human triggered slides are certain.

Current Conditions:

Snow continues to fall in the mountains this morning, with storm totals now in the 2 to 4 foot range. The snow water equivalents are astounding – averaging 3” to over 6”. Winds were strong from the southwest yesterday, averaging 20 to 40 mph. Recently, they have shifted to the northwest and are in the 15 to 30 mph range, with gusts in the 40’s. Temperatures have warmed 5 to 10 degrees since yesterday morning, and are in the mid to upper 20’s. The warm temperatures and wind inverted the snow, putting a layer of dense heavy snow on top of yesterday’s lighter snow.

Avalanche Conditions:

This storm has slammed the buried weak layers with just about every known contributory factor there is to cause avalanches – lots of snow, enormous water weights, warming temperatures, wind and rain falling on snow at the lower elevations. By yesterday afternoon, widespread avalanche activity was reported from throughout the northern Utah mountains. There was natural activity, skier triggered slides and remotely triggered slides. Some slides were running in the new snow only, while others were breaking 2 to 4’ deep into the old November weak layers.

The weak layers of surface hoar and facets are widespread. They are weakest at the lower and mid elevations, and in normally wind sheltered areas. Many slides have been occurring in terrain between 6,000 to 8,000 feet, in addition to in the upper elevations. Even in low elevation terrain, stay off of and out from under slopes steeper than about 30 degrees as it is possible to trigger slides from a distance. Large natural avalanches are occurring in some areas, so stay out from under steep slopes and avoid runout zones.

Ice Climbers – most northern Wasatch ice climbs are in avalanche tracks. With natural avalanche activity likely, ice climbing is not recommended.

Bottom Line (Salt Lake, Park City, Provo and Ogden area mountains):

The avalanche danger is HIGH to EXTREME on and below all slopes steeper than about 35 degrees, especially with recent deposits of wind drifted snow or areas receiving rain on snow. Both human triggered and natural avalanches are certain above about 6000 feet. Slopes of about 30 to 35 degrees have a CONSIDERABLE danger. Backcountry travel is not recommended.

Mountain Weather:

The moist westerly flow from the Pacific will continue to produce snow throughout northern Utah today. Areas favored by northwest flow could receive another 4 to 8 inches of snow, with 2 to 4” expected in other areas. The northwesterly winds will remain strong through early afternoon, in the 30 to 40 mph range, with gusts near 50. Highs today should be in the low 30’s at 8,000’ and near 25 at 10,000’. Decreasing winds tonight, and scattered snow showers adding a few more inches to the storm total. Temperatures will warm into the upper 20’s at 10,000’. Friday will be partly cloudy and warmer, with highs near 40 at 8,000.

Remember that UDOT may conduct avalanche control operations above the highway in Little Cottonwood Canyon at any time and will likely do so this morning. For more information, call 801-742-2927 or 801-742-2033.

Bruce will be teaching a free avalanche awareness class tonight at 7:00 pm which is open to the public. It is at the Mt. Olympus Presbyterian Church at 3280 E. and 3900 S.

If you are getting out, drop us a line or an email with any reports or observations from the backcountry. You can leave us a message at 524-5304 or 1 800-662-4140. Email us at [email protected], or send a fax to 524-6301.

The information in this advisory is from the US Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur.

I will update this advisory by 7:30 Friday morning, and thanks for calling.

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For an explanation of avalanche danger ratings:

http://www.avalanche.org/usdanger.htm