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
Sunday,
December 23, 2007 7:30 am
Good morning, this is
Current Conditions:
A clipper
passing to the northeast of us brought cloudy skies and a few flurries, but I’d
expect to see the skies opening in the afternoon. Temperatures have rebounded 15-25 degrees from
yesterday’s lows below zero and are comfortably in the mid teens at most
locations. The northwesterly winds
hounded the upper elevations blowing 20-25mph with the ridgeline anemometers
recording hourly averages of 35-45 with gusts to 60. 5”+ of settlement improved riding and trail-breaking
conditions, but the winds will take their toll.
Avalanche Discussion:
Avalanche control work
at the ski areas continue to produce very large monsters 3-5’ deep, with some breaking
to the ground in uncompacted terrain.
Highway control work in Stairs Gulch produced a 4-5’ deep crown, which
then sympathetic’ed another, smaller pocket 2’ deep. Collapsing into the interface snow prior to
last Tuesday’s storm remains prevalent, and tests indicate this layering remains
slow to heal. One skier off of Hellgate/Cardiff (google image, photo,
fracture
line profile) confirmed these suspicions as he remotely triggered a 1-2’
deep and 150’ wide avalanche on a steep west northwest facing slope above
Little Cottonwood Canyon. Collapsing the
slope on his first few turns, he watched the snow buckle 75’ below, then turned
and headed back to the ridge. Brett’s
photo gallery/outing can be found here.
New wind drifts will
be the main player today as drifts up to 2’ deep are likely to be triggered on
the steep loaded aspects. They’ll be
more prevalent on the south through easterly aspects, but watch for channeling off
the ridgelines and around the subridges and breakovers. Ski cuts, test slopes, and cornice drops
should be effective with these new soft slabs, or drifts. It’s possible these may step into the
interface from last week, producing much deep, wider slides. Remotely triggered slides are still possible
on a variety of aspects.
It’s been over a week
now that anyone triggered an avalanche into the old basal snow, and the added
snowfall from last week’s storms has made it much more difficult for folks in
the backcountry to trip the switch on these.
Nevertheless, ski areas are still able to move snow down to these layers
and it’s not taking a crow bar to pull these things out. So, there continue to be places where a
person could still trigger a slide on the weak facets near the ground. These would be in shallower snowpack areas,
including steep rollovers or in shallow rocky areas, on the steep, upper
elevation shady slopes. There slides
triggered in a shallow area will propagate into the deeper snow pack, resulting
in large, dangerous slides 3 to 5 feet deep.
Bottom Line for the
The
avalanche danger will rise to CONSIDERABLE this morning on any steep wind drifted
slopes, and may be more prevalent on south through east facing aspects. Other
slopes steeper than about 35 degrees have a MODERATE
danger, with isolated areas in the shady terrain where avalanches may step down
3-5’ deep.
Mountain Weather:
Cloudy skies will turn
partly cloudy by the afternoon. The
northwesterly winds will continue to blow 25-35mph. Temperatures will rise to the mid-twenties at
8000’ and upper teens at 10,000’. The
Christmas Eve storm looks to offer 10-16” in favored areas with a parade of
storms on its heels.
Announcements:
Wasatch Powderbirds will operate outside of the
For an avalanche education class list, updated 12/22/07, click HERE.
If you want to get this avalanche advisory e-mailed to you daily click HERE.
The UAC has temporary job openings for doing avalanche outreach in more rural
areas. Click HERE for info.
UDOT highway avalanche
control work info can be found HERE
or by calling (801)
975-4838.
Our
statewide tollfree line is 1-888-999-4019 (early morning, option 8).
For our classic text
advisory click HERE.
If you’re getting out and see anything we should know about please let us
know. You can leave 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.
I will update this advisory by 7:30 Monday
morning.