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


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Avalanche advisory

Thursday, December 19, 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 Thursday, December 19, 2002, and it’s 7:30 in the morning.


Current Conditions:

Snow showers continued in the upper Cottonwoods yesterday and last night, with additional accumulations of 2 to 9” of light density snow.  Storm totals are 1 ½ to 2 feet in the upper Cottonwoods and 14 to 20” in the Provo and Ogden mountains and on the Park City side.  There are reports of 3 feet in parts of the western Uintas.


This morning, skies are partly cloudy and temperatures are in the frosty single digits to low teens.  Winds are from a westerly direction, averaging 10 to 15 mph, with gusts in the mid 20’s.  On a few of the highest peaks, hourly averages are in the mid 20’s, with higher gusts. 


Avalanche Conditions:

Slides continued to be easily triggered yesterday, both by people and explosives, and there were many reports of widespread cracking and collapsing in the backcountry.  This indicated that the buried weak layers have not adjusted to the weight of the new snow yet, and that the simple weight of a person is enough to tip the balance.


A more defined pattern of the avalanche activity is emerging.  Most of the natural and human triggered activity has been on northwest, north, northeast and easterly facing slopes, with a few slides on west and southeast.  The slides are averaging 1 to 2’ deep, with wide variation in width - from enormous 1000’ wide slides to small pockets of 50’. Some have been on slopes less steep than 35 degrees.  All the slides are breaking in the old snow, in one of the several layers of weak facets.  It is worth noting that slopes which were largely bare a week ago have better stability, as they do not contain this underlying weak layer. However I would caution against making assumptions solely based on slope aspect.  One mistake could result in nasty consequences.


A significant number of slides have broken well off the ridgelines, leaving a large amount of snow hanging in place above the crown.  There have been numerous reports of people triggering 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.


The key to safe travel in the backcountry today will be watching your slope angles - stay off and out from under steep slopes.


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

The avalanche danger is CONSIDERABLE today on west through north through east facing slopes above 7,500’.  Human triggered avalanches are probable, and natural avalanches are possible.  With strong southwest winds in the forecast for tonight, expect the avalanche danger to increase again by Friday morning.


Mountain Weather:

After a few lingering snow showers this morning, skies should become mostly clear as a short lived ridge moves over the area.  The northwesterly winds will average 10 to 20 mph across the higher ridges, and shift to the southwest by late afternoon.  Highs today will be in the mid teens at 10,000’ and near 20 at 8,000’.  For tonight, increasing clouds and strong southwest winds developing ahead of the next storm system, which should spread snow into northern Utah by dawn.  A moist, unstable flow will keep snow showers going through Sunday morning.


General Information:

The Friends of the Utah Avalanche Center will offer an intensive 3-day avalanche class January 18-20.  You can sign up at the Black Diamond Retail Store or call them at 278-0233.


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 [email protected] 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.


Tom Kimbrough will update this advisory by 7:30 on Friday morning.


Thanks for calling!




National Weather Service - Salt Lake City - Snow.

For an explanation of avalanche danger ratings: