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

 

: http://www.avalanche.org/~uac/

 

Avalanche advisory

THURSDAY, NOVEMBER 13, 2003   7:30 am

 

Good morning, this is Evelyn Lees with the Forest Service Utah Avalanche Center with your avalanche and mountain weather advisory.  Today is Thursday, November 13, 2003, and it’s 7:30 a.m. 

 

Current Conditions:

A strong, moist upper level low will work its way across northern Utah today and tonight.  Ahead of the low, southeasterly winds have been blasting across the range for the last 12 hours.  At 10,000’ the hourly averages have been in the 25 to 30 mph range, with gusts near 50.  Precipitation in the mountains has just started, with stations reporting two to five inches of new snow.  Temperatures this morning are in the low to mid 20’s at 10,000’.  If you’re looking for turns today, think of the most wind sheltered area you can imagine.  The upper elevations and any open slopes will be a mix of wind scour and wind drifts.  Reports indicate the winds getting well down into the mid and lower elevations.

 

Avalanche Conditions:

There are two avalanche problems for today.  The first is the new wind drifts or wind slabs.  On steep slopes, I would expect many of these new wind drifts to break under the weight of a person.  Some of today’s new drifts will be very sensitive, while others will be the more stubborn hard slabs.  The hard wind slabs will allow you to get partway down a slope before they break above you.  Strong winds often load snow in unusual places, further down slope and at lower elevations than one would normally expect.  It may be hard to detect which slopes have wind drifts as they get hidden by the new snow. 

 

The second problem is the more deeply buried surface hoar layer.  There was another skier triggered avalanche yesterday in upper Big Cottonwood Canyon, and once again the culprit was surface hoar, this time sitting on a sun crust.  It was on a 35 to 38 degree easterly facing slope at 9,700’.  In both the Ogden and Provo area mountains, areas of buried surface hoar extend from the ridges down to about 8,000’.  The pattern in the central Wasatch is less known, but buried surface hoar is fairly wide spread at the higher elevation in upper Big and Little Cottonwood, and I think it is likely there are pockets at the mid elevations, too.  The weak snow is not limited to just the shady slopes.  There is also a mix of sun crusts and facet sandwiches on the “sunny” slopes – east through south through west.   Any avalanches involving the more deeply buried surface hoar or facets have the potential to be larger, deeper and possibly triggered from a distance.

 

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

Today, the avalanche danger is CONSIDERABLE on all slopes steeper than 35 degrees, especially those with recent drifts of wind blown snow.  Considerable means natural avalanches are possible, and human triggered avalanches are probable.  The avalanche danger is MODERATE on 30 to 35 degree slopes with recent drifts of wind blown snow.  The avalanche danger may increase through out the day if we get the additional wind and snow forecast, and the danger may rise to HIGH this afternoon or tonight.  

 

Provo area mountains: The avalanche danger in the Provo mountains is CONSIDERABLE on slopes steeper than about 30 degrees.  In these areas, human triggered avalanches are probable and natural avalanches possible.  The danger in the Provo area mountains increases with elevation.  The avalanche danger may increase through out the day if we get the additional wind and snow forecast, and the danger may rise to HIGH this afternoon or tonight.

 

Mountain Weather:

A snowy and very windy day is in store for the northern mountains.  An additional 5 to 8 inches of snow is expected today.  Winds will gradually shift from the southeast to the southwest today, and decrease from this morning’s 30 mph speeds into the 20 to 25 mph range this afternoon.  Temperatures will remain in the low 20’s at 10,000’.   Tonight, an additional 5 to 10” of snow is possible, with moderate winds turning to the northwest after midnight.  Snow showers may linger into Friday morning.  A weak ridge will move across the area Friday afternoon, and more snow is likely this weekend.

 

General Information:

If you are getting into the backcountry, please give us a call and let us know what you’re seeing, especially if you trigger an avalanche.  You can leave a message at 524-5304 or 1-800-662-4140.  Or you can e-mail an observation to [email protected] .org, or you can fax an observation 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. 

 

Andrew McLean will update this advisory Friday morning.

 Thanks for calling!

_____________________________________________________________________________

For more detailed weather information go to our Mountain Weather Advisory

National Weather Service - Salt Lake City - Snow.

For an explanation of avalanche danger ratings:

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