Sun Valley Avalanche Bulletin
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This bulletin is from the Sawtooth National Forest Avalanche Center in Idaho.
Sawtooth National Forest Avalanche Advisory 
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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.
SPRINGTIME CONDITIONS:
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.
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