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

Friday, December 20, 2002

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Good Morning.This is Tom Kimbrough with the Forest Service Utah Avalanche Center with your backcountry avalanche and mountain weather advisory.Today is Friday, December 20, 2002, and itís 7:30 in the morning.

 

Current Conditions:

More stormy weather is headed our way this morning.Although it looks like the major thrust of the current storm will miss the Wasatch to the south, we should still get several inches of new snow and plenty of wind.Several of the mountain weather stations are on the fritz this morning but it looks like ridge top winds are 20 to 30 mph with gusts of 50 and 60.Temperatures have warmed during the night and are now in the teens and low twenties.There doesnít seem to be any new snow overnight but storm totals from Monday through Wednesday are about 16 inches to over 2 feet.

 

Avalanche Conditions:

Again yesterday there were plenty of avalanches, both from control work and human triggered.The layer these slides are releasing on is called faceted snow.It was formed during the long dry spell and produces notoriously long lasting and persistent instabilities. As we go into the weekend, donít expect the backcountry conditions to get safer and indeed, with todayís wind and new snow, we will bump right back up to HIGH danger in some areas. There were many reports of widespread cracking and collapsing in the backcountry yesterday plus quite a few remotely triggered slides and a couple of people caught but not completely buried or hurt. A party on the north side of the ridge above Pole Line Pass between Big and Little Cottonwood remotely triggered a slide that ran over a couple of guys on the opposite side of the ridge.

 

The one saving grace to our situation is that many slopes avalanched naturally during the storm but, as usual, there are a couple of catches.First of all, it is often hard to tell for sure if a slope did slide if additional new or wind blown snow has covered the evidence.Secondly, many of the slopes that did run during the storm only partially released, leaving lots of snow still hanging in the balance.The east facing slope above Pole Line Pass that caught two skiers fits this pattern.Part of the slope had been released by highway control work the previous day.

 

Another tip is that southerly facing slopes have had little or no avalanche activity because areas that were largely bare a week ago donít have the underlying weak layers.The catch here is that this window is fairly narrow with plenty of activity on west, east and even southeast facing slopes.The best defense at this time is carefully watching slope angles, staying down close to or below 30 degrees steepness.The catch to this caveat is that slides are being triggered remotely so if there is a steeper slope above you, you could easily trigger it from below. Also, slopes triggered remotely may take out adjacent lower angle terrain.

There have been plenty of 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.In all areas, collapsing and cracking are clues to the instability.

I am getting reports indicating that this morningís winds are getting down into mid and lower elevation terrain as well as along the high peaks and ridges.With literally tons of light snow lying around, these winds will quickly increase the avalanche danger on all wind affected steep slopes.

 

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

The avalanche danger is HIGH today on all steep slopes with wind drifted snow.Out of wind affected terrain the danger is CONSIDERABLE on west, north and east facing slopes above about 7,000í.Human triggered avalanches are probable, and natural avalanches are possible.

 

Mountain Weather:

Although this doesnít look like another big storm the Wasatch should still get several inches of new snow today.Winds will be strong, 20 to 30 mph with stronger gusts through mid day, decreasing this afternoon.Highs today will be in the lower twenties at 8,000 feet and in the teens at 10,000.The weather will continue unsettled through the weekend with additional snow and wind likely.

 

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.

 

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

 

Thanks for calling!

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National Weather Service - Salt Lake City - Snow.

For an explanation of avalanche danger ratings:

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