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| 4.7.2008 |
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This is Chris Lundy with the Sawtooth National Forest Avalanche Center with our last advisory of the season on Monday, April 7, 2008.
For a daily mountain weather forecast for our area, click the link below. The NWS will keep this winter-time product going until April 15th.
http://www.wrh.noaa.gov/pih/avalanche/index.php
For real-time weather station data until mid-May check:
Titus Ridge: http://www.sawtoothavalanche.com/wx_titus.php
Lower Titus: http://www.sawtoothavalanche.com/wx_lower.php
Bald Mountain: http://www.sawtoothavalanche.com/wx_baldy.php
Avalanche Conditions:
Spring has not really arrived at upper elevations where a cold, winter-like snowpack remains. This means you’ll want to continue to treat the snowpack like you would mid-winter, looking for potential weak layers and evaluating the stability of those layers.
Another concern will be when spring does finally arrive in earnest. When the spring-time heat inevitably turns on, watch out for periods when overnight temperatures remain above freezing, especially if this lasts for a few days or more. Under these conditions, our upper elevation snowpack may go “isothermal” which is a fancy way of saying that liquid water is present throughout the entire snowpack. The first time this happens in the spring, it comes as quite a shock to the snowpack and can lead to unstable conditions and large, dangerous wet avalanches. Once the snowpack figures out what to do with the liquid water, the snowpack tends to become more stable, especially with overnight temperatures below freezing.
Intensive warming often makes cornices more susceptible to breaking off, especially with the added weight of a person. They may break back much further and wider than you anticipate. Cornices are quite large this year from all of our wind events.
Below are some avalanche safety tips for spring backcountry sliding and riding.
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 Deer Creek Fund in the Idaho Community Foundation, 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 are 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
WILDLIFE SPECIAL CONCERNS: Whether you are down along the valley floor, out our side canyons or up in the mountains, please don’t force wildlife to move around. Motorized and non-motorized recreationists and dogs disturb wildlife.
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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