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/

Avalanche advisory

Wednesday, December 11, 2002

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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 11, 2002, and it’s 7:30 in the morning.

Current Conditions:

Is this really the Wasatch – since when did a measly couple of inches of snow create such interest and excitement? But as these few inches may herald the start of a pattern change back to winter, then they do deserve special note. As of 6 am, the mountains around Salt Lake and Park City have received up to 2” of new snow. As far as I can tell, an inch or less has fallen in the Ogden, Logan and Provo mountains. Temperatures are in the mid teens at 10,000’ this morning, and winds are from a westerly direction. Across the highest ridges and peaks, hourly averages are 15 to 20 mph; once off these high ridgelines winds are light, averaging less than 10 mph.

Avalanche Conditions:

While last night’s 1 to 2” of snow hasn’t significantly increased the avalanche danger yet, the avalanche danger will be on the rise today if we receive the additional snow and stronger winds that are forecast. Remember that conditions may change rapidly.

The past four weeks of almost completely dry weather has melted the snow off south facing slopes and seriously weakened the snow surface on many other slopes. The weakest surface conditions are above 9,000 feet on northwest, north and northeast facing slopes.

In these areas, the new snow is landing on a mix of big flakes of surface hoar, which look crystalline feathers and corn flakes, and other sugary weak crystals. East and west facing slopes that still have snow also have plenty of these big crystals, often on top of crusts of varying thickness. So as the snow builds up, expect activity on these aspects as well.

For today, in areas with about 1-3” of new snow, expect loose snow sluffs on steep slopes, perhaps running far in the more continuously steep terrain. If snowfall amounts or wind blown drifts reach about 6” or more, expect very sensitive soft slabs to break out on steep slopes. While initially small and shallow, these new snow soft slabs will become increasingly reactive as snow depths increase. The shallow slabs may not carry a lot of punch, but they could be enough to knock you off your feet and take you for a rough, rocky ride.

Keep in mind that this new snow may effectively hide and protect the near surface facets and surface hoar deposits, potentially setting us up for a nasty round of avalanches when a larger storm arrives.

Bottom Line (SLC, Park City, Ogden and Provo Area Mountains):

While the avalanche danger remains LOW this morning, additional snow and/or wind today will increase the danger to MODERATE. In any areas with snow amounts of about 6 or more inches, including wind drifts that deep, the avalanche danger is MODERATE on steep slopes with preexisting old snow.

Mountain Weather:

A weak low pressure system moving north of us through Idaho and Wyoming will produce light snow throughout most of today and tonight. Additional accumulations of 1-3 inches today and again tonight are expected, with locally higher amounts possible. The winds will shift to the northwest, and increase, averaging 15 to 25 mph. Highs today will be much cooler, in the upper teens at 10,000’ and the low 20’s at 8,000’. After a break on Thursday, there will be increasing clouds and southwest winds Thursday night and Friday ahead of the next weather systems which are anticipated for Sunday and Monday.

General Information:

Bruce will be giving a free avalanche awareness talk for the Wasatch Mountain Club on Thursday night, December 12^th, at 7:00 pm at the Zion Lutheran Church on Foothill Drive. The talk is open to the public.

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.

Ethan Greene will update this advisory by 7:30 on Thursday morning.

Thanks for calling!

________________________________________________________________________

National Weather Service - Salt Lake City - Snow.

For an explanation of avalanche danger ratings:

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