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This is Janet Kellam with the Sawtooth National Forest Avalanche Center with General Snow and Weather Information on Friday, April 10, 0109.
This is our last update, so we have included some avalanche safety tips for spring backcountry sliding and riding. Thank you everyone, for your support this winter.
I'd like to emphasize to all backcountry travelers to be very cautious in any steep, rocky terrain for the remainder of the season at upper elevations. Our long mid winter dry spell created very weak snow near the base of the snowpack and it will remain possible to trigger a large, destructive avalanche in areas where the weak snow persists. Due to much wind accompanying our spring storms, extremely variable snow depths cover the weak layer.
Shallow areas of snow cover increase the risk of the weight of a person or machine collapsing the weak underlying snow and triggering a slide. Recent snowfall and warming temperatures also increase the risk of triggering a slide on this layer. Tracks on a slope do not mean it is safe.
The best risk management is avoidance of steep rocky terrain for at least several days whenever we experience new snowfall, especially when followed by spring sunshine or warming temperatures. In general, old facet layers are deeply buried and remain dormant, but isolated human triggered and natural avalanches at upper elevations that occurred in early April are reminders that we can't forget about them entirely.
In addition, we expect a large avalanche cycle at upper elevations when we begin to experience overnight temperatures above freezing.
SPRINGTIME BACKCOUNTRY BASICS:
Timing: Get out early, follow the sun as slopes heat up and be home by early afternoon. There's great snow conditions to be had, but stay heads up in alpine areas and at upper elevations where the snowpack may be more winter-like.
New Snow: New snow will be more sensitive to the sun's heating than older snow. Spring temperatures and sunshine are intense and will initially decrease the stability of any new snowfall on steeper slopes. Watch for newly formed wind slabs on crusty layers or lighter density snow. It is still important to dig down and see just how well the snow layers are bonded together, how wet or how weak the underlying snowpack may be.
Temperatures: Pay close attention to how deep the overnight freezes penetrate the snowpack. Watch for spring rain events or a dramatic warm-up, either of which lead to increased avalanche danger. Clear skies help to promote a good freeze, clouds create a greenhouse warming effect.
Safe Travel Practices: We continue to recommend safe travel practices such as one person exposed on a slope at a time, closely watch each other, carry avalanche beacons, probes and shovels and be well practiced with them.
SPECIAL THANKS to all our sponsors this season for their generous support!!
The Friends of the Sawtooth Avalanche Center, The City of Ketchum, Blaine County Search and Rescue, the Twin Falls-Shoshone BLM, the Idaho State Department of Parks and Recreation, the Wattis Dumke Foundation, the Sawtooth Society, Sun Valley Telemark Series, Smiley Creek Lodge, Idaho Power Company, The Elephant's Perch, Woodside Motorsports, and Backwoods Mountain Sports.
And most of all, thanks to all of you for being a part of the Avalanche Center!
See you next season!
Announcements:
Your observations continue to be invaluable - they help us produce more accurate advisories which in turn helps you. If you get into the backcountry, let us know what you see out there - especially if you see or trigger any avalanches. Call (208)622-0099 or fill out the observer form on our web site. http://www.sawtoothavalanche.com/submit_observation.php
The Avalanche Beacon Park has been taken down for the season.
Please avoid all game animals throughout the valley in springtime and steer clear of mountain goats in the high country.
For all US avalanche accident reports go to www.avalanche.org
Check http://www.wrh.noaa.gov/pih/ for the latest weather forecasts.
For Idaho road closures and openings check: http://511.idaho.gov/
For a recording of this advisory, call the Avalanche Hotline - (208)622-8027.
This information only applies to the backcountry and does not apply to highway programs or operating ski areas. Changing conditions and local variations may occur.
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