In partnership with: Utah Division of State
Parks and Recreation, The Friends of the Utah Avalanche Center, Utah Department
of Emergency Services and Homeland Security and
“keeping
you on top”
AVALANCHE ADVISORY
Tuesday,
January 29, 2008 7:30 am
Good morning, this is
Bruce Tremper will be giving a free talk at the SLC
REI tonight at 7pm called The Science of Avalanches.
Current Conditions:
Let’s reconstruct the
last 30 hours or so. 3-8” of mostly
graupel and rimed crystals fell in the early Monday morning hours prior to the
cold front, which arrived around 11am. Lightning
and gusts over 100mph preceded, at times, snowfall rates of 3-4”/hour, piling
up the snow in a hurry and producing widespread, if relatively shallow, natural
avalanching at a variety of aspects and elevations. Temperatures dropped into the single digits,
with many stations dropping to 7 or 8 degrees below zero. The winds veered back to the northwest with
the passing of the cold front, and snowfall favored the Cottonwoods, though
much of the range received a good blast of snowfall. Lingering showers overnight added another
1-3”, pushing storm totals to nearly 2’ in the Cottonwoods, 8 and 16” in the
Ogden and Park City mountains, and about 4-6” in the Provo mountains. The winds refuse to buckle, and have remained
strong, blowing 25-35 mph with the most exposed stations suffering hourly
averages of 45-55 mph, gusting to 80.
Wind chill temperatures are currently calc’d to -45 degrees Fahrenheit
at 11,000’.
Snow and Avalanche Discussion:
Ski areas and UDOT
explosive work produced many new slides in the new snow, with a few pulling out
into older layers at the lower elevations on the
Numerous stiff wind drifts up to and over 3’ deep will be scattered
throughout the standard starting zones and less obvious areas. Strong winds ahead of and behind the front
will have alternated eroding and loading patterns, so the patchwork of wind
effect will be complex and tricky, and likely ill-defined by convention or
pattern with respect to aspect and elevation.
The deposited hard
slabs will only be stiffened and, in many areas, difficult to trigger due
to the colder temperatures, but may be difficult to escape once triggered. The hard slab phenomenon here may allow
multiple tracks or a skier or rider well onto the slope before they trigger the
thin spot allowing the slope to fail.
Likely unsurvivable. Multiple
potential weaknesses include the graupel prior to the storm, intra-storm
weaknesses, and localized sheets of surface hoar and faceted grains from brief
interludes of high pressure last week.
Collapsing and hollow sounds are clues to local instabilities. Cornices, while stiff, may break back farther
than expected. Slope cuts will likely be
ineffective and dangerous and single snow pits will be wildly inconclusive, if
wholly unrepresentative.
Bottom Line for the
The danger
is CONSIDERABLE on any
steep wind drifted slope. It will be possible to trigger avalanches
with severe consequences in localized terrain. For LOW danger,
look for protected gladed low angle slopes less steep than 30 degrees that are
not underneath or ‘attached’ to adjacent steeper terrain.
Mountain Weather:
We’ll see some break
in the clouds, warming temperatures, and gently backing winds ahead of
tonight’s next vigorous storm.
Temperatures at 10,000’ will ‘warm’ to 10 degrees as 8000’ temps push
into the low teens. The mellowing
southwesterly winds today will blow 20-30mph, only to increase again ahead of
the strong cold front overnight. 12-16”
can again be expected in areas favored by a northwest flow, with the
Announcements
Yesterday, the Wasatch Powderbird Guides
didn’t get out. If weather permits they
will be flying in
The second annual avalanche awareness
snowmobile ride is Saturday, February 2nd and proceeds will help
support snowmobile specific avalanche awareness projects. Details can be found at http://www.avarides.com/
Backcountry Awareness Week is February 8-10th,
featuring a Friday night fundraising dinner with guest speaker David Oliver
Relin, author of the New York Times bestseller Three Cups of Tea: One Man's
If you want to get this avalanche advisory e-mailed to you daily click HERE.
UDOT highway avalanche control work info can be
found by calling (801) 975-4838.
Our statewide tollfree line is 1-888-999-4019 (early morning, option 8).
The UAC depends
on contributions from users like you to support our work. To find out
more about how you can support our efforts to continue providing the avalanche
forecasting and education that you expect please visit our Friends page.
If you see any avalanches or interesting snow conditions, please leave us a
message at (801) 524-5304 or 1-800-662-4140, or email us at [email protected].
(Fax 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.