Wasatch Cache National Forest

In partnership with: The Friends of the Utah Avalanche 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 10, 2004 7:30 Am         

 

Good morning, this is Evelyn Lees with the Forest Service Utah Avalanche Center with your backcountry avalanche and mountain weather advisory.  Today is Friday, December 10, 2004, and it’s 7:30 am. 

 

An Avalanche Warning remains in effect for the northern Utah mountains and extreme southeast Idaho through midnight tonight.  Recent snow, strong winds and rapidly warming temperatures today will keep the avalanche danger High.  Avalanches are occurring at unusually low elevations in addition to the more typical mid and upper elevations. 

 

Current Conditions: 

The storm has moved out, leaving behind storm snow totals ended up in the 2 to 4 foot range, with whooping snow water equivalents of 4 to 7”.  Temperatures are on an unstoppable march upward this morning – already near 30 degrees at 9500’ and at some of the lower elevations they have been above freezing all night.  Winds are from the northwest, averaging 10 to 15 mph, except across the highest terrain where hourly averages are closer to 25 mph.

 

Avalanche Conditions:

Yesterday, explosive control work in the SL, Park City and Ogden area mountains released a number of long running, tree breaking avalanches.  Even with limited visibility, there was evidence of a decent natural avalanche cycle in the backcountry, including widespread activity at low elevations in the Ogden area mountains.  Careful backcountry travelers intentionally triggered slides (photo) in upper Big Cottonwood and on the Park City side, many remotely.  They were up to 3’ deep and 100’ wide, breaking into the November facets.  There were many reports of widespread cracking and collapsing, including below 8,500’.

 

There are a lot of slopes out there that did not slide and are just waiting for a trigger, including lower and mid elevation terrain and wind sheltered areas.  So in all backcountry terrain, the key to staying safe will be watching your slope angles.  It is possible to trigger slides from a distance, so be aware of what is above you and to the side of you.  Stay off of and out from under slopes steeper than about 30 degrees.  Terrain traps are common at the mid and low elevations, where even a small avalanche can pile snow up deeply, and this dense snow will set up like wet cement. 

 

And finally, one more rapid change is in store for the already overloaded snowpack. Dramatically warming temperatures and direct sun will increase the danger on and below steep sunny slopes, and at the mid and lower elevations.  Also remember that most northern Wasatch ice climbs are in avalanche tracks.

 

Bottom Line (Salt Lake, Park City, Provo and Ogden area mountains): 

The avalanche danger is HIGH on and below all slopes steeper than about 35 degrees, above about 7000 feet.  Human triggered avalanches are likely.  Slopes of about 30 to 35 degrees have a MODERATE danger.  The avalanche danger on and below steep, sunny slopes and at lower elevations will increase with daytime heating.

 

Mountain Weather:

The strong ridge of high pressure building into the area today will have you thinking of sunscreen and pineapples.  Skies will clear today, and temperatures rise into the mid 40’s at 8,000’ and into the mid 30’s at 10,000’.  Winds will gradually decrease to less than 15 mph and switch to the southwest.  It will be clear and mild tonight, with 10,000’ temperatures near 40, and warm and sunny on Saturday.

 

If you are getting out, drop us a line or an email with any reports or observations from the backcountry.  You can leave us a message at 524-5304 or 1 800-662-4140.  Email us at [email protected], or send a fax to 524-6301. 

The information in this advisory is from the US Forest Service, which is solely responsible for its content.  This advisory describes general avalanche conditions and local variations always occur. 

Bruce will update this advisory by 7:30 Saturday morning, and thanks for calling.

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For an explanation of avalanche danger ratings:

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