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

Saturday, December 21, 2002

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Good Morning.This is Bruce Tremper with the Forest Service Utah Avalanche Center with your backcountry avalanche and mountain weather advisory.Today is Saturday, December 21, 2002, and itís 7:30 in the morning.


Current Conditions:

With a mighty one inch of new snow overnight and three in the past 24 hours, this weak storm isnít impressing me much.Most of the energy from the storm is heading south of us and I donít think weíll get much more.The south facing slopes are sun crusted, thereís some wind damage along the ridge tops and the northerly facing slopes still have some nice powder, but it has gotten thicker from the very nice snow yesterday.


Avalanche Conditions:

We heard of four more human triggered avalanches that occurred in the backcountry yesterday.A skier triggered a steep wind slab in Hidden Canyon near Brighton about 20 feet wide.Another skier intentionally ski cut a hard slab in Dayís Fork 60 feet wide and ran 500 feet. A person wandered out into terrain that was too steep and triggered a slide in Silver Fork 100 feet wide and a snowmobiler triggered an avalanche on the road cut down low in Cardiff Fork.All of these are about two feet deep and running on the old, weak faceted snow.Weíve started posting a more detailed list of avalanche activity on our web site (click HERE).You can find it at www.avalanche.org, click on Salt Lake, and then on Advisories.In this same place you can find photos of recent avalanches.


Although the avalanches are harder to trigger than a couple days ago, as you can see, things are still plenty sketchy.When the storm earlier in the week slammed two feet of snow down on top of the astounding weak layers of depth hoar, it initiated probably the most widespread avalanche cycle I have seen in my 17 years in the Wasatch.About 80-90 percent of all the slopes steeper than about 38 degrees slid during the storm.This means that some steep slopes are still hanging in the balance and quite a few slopes between about 35 degrees and 38 degrees are also waiting like a crouching mountain lion for a victim to bumble into the trap.This type of weak layer is notoriously persistent and itís going to take at least until after the weekend for things to settle down.If this isnít enough, the winds blew yesterday morning 20-40, gusting to 50 from the west along the highest ridge tops, which created some areas of hard wind slabs that people were able to trigger yesterday.


This doesnít mean that itís dangerous everywhere.The hot tip for the day is to do one of three things:First, the south facing slopes are significantly more stable than the north facing ones because the new snow fell mostly on bare ground or snow stabilized by the heat of the sun. The downside is that these slopes will be rocky and sun crusted. Second, if you must go the steep slopes on shady aspects, you can have a good time on slopes that slid during the storm, which should be fairly safe as long as you donít tickle the snow hanging above the fracture line. The bad news is that itís hard to tell what slid during the storm and what didnít because most of the slides are now covered up by a foot of new, and wind-blown, snow. Also, these slopes tend to be rocky because some of the snow was removed during the slide.Finally, you can go to a slope on a shady aspect that did not slide during the storm.The bad news is that anything steeper than about 35 degrees will likely slide so youíll have to diligently watch your slope angles.I wouldnít get much steeper than 30 degrees myself.


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

The avalanche danger is CONSIDERABLE today on all steep slopes with wind drifted snow.The danger is also CONSIDERABLE on northwest, north, northeast and east facing slopes above about 7,000í steeper than about 35 degrees, and MODERATE to LOW on steep southeast through southwest facing slopes or on steep slopes that slid during the storm.


Mountain Weather:

Tonight at 6:14 pm is the winter solstice, meaning that today is the shortest and darkest day of the year.With most of the energy from this storm heading south of us, weíre left with the worst parts of the stormójust poor visibility, cold temperatures and very little snow.Today expect temperatures quite chilly in the single digits along the ridge tops and rising into the teens later in the day down at 8,000í.Ridge top winds should be 20 mph from the west this morning and becoming light and variable by afternoon.Looks like a few lingering clouds on Sunday and clearing out on Monday.Next chance for snow is about next Thursday.


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.


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


Thanks for calling!



National Weather Service - Salt Lake City - Snow.

For an explanation of avalanche danger ratings: