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
Saturday, February 22, 2003
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Good Morning. This is Bruce Tremper with the
Ridge top winds this morning have diminished somewhat. Yesterday, they were blowing hard from the west at 30mph and gusting to 50 along the highest peaks and they drifted quite a bit of snow on the upper elevation ridges. This morning, ridge top winds are from the west, blowing around 15-20 with ridge top temperatures in the mid teens.
Today the big news is a very welcome snow storm. The cold front should arrive around the morning and it looks like we will get 6 inches to as much as a foot of new snow by tonight when things slow down.
So how is this going to
affect the avalanche danger? Like most
avalanche questions--it depends. The
first rule of avalanche forecasting is that you start with the pattern of the pre-existing
snow. Most of the snow in northern Utah
at upper elevations is fairly deep and stable, so the weight of the new snow
probably won’t affect it too much unless we get much more snow than we expect. But the big, scary exception is that some
places have a thin and consequently weak snowpack and any additional weight
will make it cranky. A week ago today, a
backcountry skier triggered an avalanche on Gobbler’s Knob, which killed him in
exactly this kind of situation on a steep, shallow snowpack, which had been recently
loaded with the weight of new snow. In a
more recent example, yesterday, some backcountry skiers in No Name Bowl on the
The second problem is that yesterday the wind blew hard along the ridges and a number of people, myself included, found localized areas of fresh wind drifts on steep slopes that we could trigger easily. Today’s new snow will cover up those wind slabs, making them invisible. Today, you should definitely be suspicious of steep slopes in upper elevation, wind-exposed areas, especially east through south facing slopes. If you must mess around with them, kick some cornices first and put in a good slope cut before you commit yourself.
Bottom Line (SLC,
The avalanche danger is CONSIDERABLE at upper elevation, wind exposed, steep slopes with recent deposits of wind drifted snow. There is also a MODERATE or localized danger of triggering an avalanche on deeper weak layers of old, weak, faceted snow on slopes that face northwest, north, northeast and east, steeper than about 35 degrees and above about 9,000 feet, especially in thin, rocky areas and the danger will likely rise to CONSIDERABLE later today in this kind of terrain.
As I said, 6 inches to perhaps
a foot of snow today. Remember that
probably only 4-wheel drive or chains will be allowed in Little Cottonwood
Canyon today. The storm will start with
westerly ridge top winds and they will turn northwesterly by afternoon. Ridge top temperatures today should be in the
mid teens and drop to around 5 degrees overnight with 30 mph winds from the
west this morning, swi
To report backcountry snow and avalanche conditions, especially if you observe or trigger an avalanche, please leave a message on our answer machine at (801) 524-5304 or 1-800-662-4140, or email to [email protected] or fax to 801-524-6301. Your information could save someone’s life. 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 on Sunday morning.
Thanks for calling!
For an explanation of avalanche danger ratings: