Wasatch Cache National Forest

In partnership with: The Friends of the Utah Avalanche Forecast Center, Utah Department of Public Safety Division of Comprehensive Emergency Management, Salt Lake County, and Utah State Parks

The Utah Avalanche Center Home page is: http://www.avalanche.org/~uac/

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Avalanche advisory

Wednesday, December 29, 2004

Good morning, this is Evelyn Lees with the Forest Service Utah Avalanche Center with your backcountry avalanche and mountain weather advisory. Today is Wednesday, December 29, 2004, and its 7:30 in the morning.

During major storms, UDOT may conduct avalanche control operations above the highways in the Cottonwood Canyons and Provo Canyon at any time. For more information call 801-742-2927 or 801-742-2033. UDOT will be doing control work in Provo Canyon tomorrow, Thursday, December 30^th. The ice climbing from the Bridalveil/Nunns Park parking lot to Frazier Park will be closed from 10 AM until control work is complete.

Current Conditions:

A strong, moist pacific storm system will be over northern Utah through tonight. Snowfall started just before midnight and as of 6 am, snowfall rates are generally 1 to 2” hour, with most stations reporting 6 to 8” of new. Densities are around 10%. The southeasterly winds have temporarily quieted down, and are in the 15 to 25 mph range across the higher ridges. Temperatures are in the low to upper 20’s.

Avalanche Conditions:

The avalanche danger is rapidly rising, and historically, many avalanche accidents happen on days of increasing avalanche danger. There are some reports this morning of a density inversion within the new snow, which will form a weak layer. Beneath the new snow, the old snow surface is a complex patchwork of crusts, wind slabs, and some loose snow, with weaker snow at mid and low elevations in many areas. The new snow will not bond well to some of these old snow surfaces, including the slick crusts on the southerly facing slopes. In addition, the moderate to strong southerly winds will blow the snow into sensitive drifts 2 to 3 feet deep by afternoon. I expect it will be easy to trigger new snow avalanches on steep slopes on most aspects and elevations, especially in wind drifted areas. As the storm continues, slides may break into one of the more deeply buried weak layers.

If you head into the backcountry today, chose a trip with lots of options, including lower angle slopes without steep slopes above. If you observe any increases in wind speeds or snowfall rates, the avalanche danger will also be increasing more rapidly. Evaluate every slope very carefully as conditions change in very short distances of even 2 or 3 turns, both across and up and down the slope.

Bottom Line:

The avalanche danger is rising and will rapidly reach CONSIDERABLE on slopes steeper than about 35 degrees. Considerable means natural avalanches are possible and human triggered slides probable, so avalanche runout zones should be avoided. With additional snowfall and strong winds forecast, the avalanche danger may reach HIGH in some mountains areas by tonight. On slopes between about 30 to 35 degrees, the avalanche danger will rise to MODERATE.

Mountain Weather:

A moist, unstable southwesterly flow will remain over northern Utah through Thursday. Today, snow, heavy at times, with an additional 8 to 14 inches possible. The snow level varies between 6,000 and 7,000’ and will drop to near the valley floors by tonight. Winds will shift to the southwest and increase into the 25 to 35 mph range this afternoon. Temperatures will be near 30 at 8,000’ and in the low 20’s at 10,000’. There is about a 30% chance of lightning this afternoon. Tonight, an additional 6 to 10” of snow is possible and the southwesterly winds will continue to blow in the 25 to 35 mph range. Temperatures will drop into the mid teens at 10,000’. Snow showers and breezy Thursday, with another colder storm forecast for Friday afternoon into the New Year.

The Wasatch Powderbird Guides flew in Cardiff, Days, Silver, Grizzly, White Pine and American Fork yesterday and if they can fly today they will be in Cardiff, Days, Silver, Grizzly and American Fork.

Registration for the Friends of the Utah Avalanche Center’s 3-day January avalanche class is now being taken at the Black Diamond retail store.

Free Beacon Rescue Training Centers are now open at Snowbird and the Canyons. For more information go to wasatchbackcountryrescue.org.

We do an early morning update around 6am each day on the 364-1591 line.

To report backcountry snow and avalanche conditions, especially if you observe or trigger an avalanche, call (801) 524-5304 or 1-800-662-4140, or email to uac@avalanche.org or fax to 801-524-6301. The information in this advisory is from the U.S. Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur.

Bruce Tremper will update this advisory by 7:30 on Wednesday morning.

Thanks for calling

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For an explanation of avalanche danger ratings:

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