The report and video below are from the Sawtooth National Forest Avalanche center's website and YouTube channel . The tragedy at the Sun Valley Resort is a good reminder to "know before you go". The Avalanche Center is a tremendous resource with valuable information as well as schedules of training.
Yesterday was another busy day for avalanches in the Wood River Valley. We had reports of slides on Minebender that probably ran Friday; these were wide and debris from one reached the valley bottom. A skier triggered a small slide in bounds at Baldy, and natural avalanches were visible on Durrance and in Anderson and Buccal Creeks. A party on Prairie Peak reported widespread whumpfing and collapsing and skiers in Timber Bowl remotely triggered a slab 2-3 or more feet deep yesterday afternoon. Yesterday evening, a series of natural avalanches on the east face of Della temporarily blocked the river near Hailey in three places; the powder cloud reportedly dusted a man walking his dogs and two men were stranded on the far side of the river after crossing one debris dam before it washed away. They were eventually rescued by the Hailey Fire Department.
We are dealing with a dangerous snowpack. I’ll repeat that, because any details about it aren’t nearly as important as that conclusion: we’re dealing with a dangerous snowpack. In some places it’s easier to trigger a slide; in others, the snowpack is not hair-trigger sensitive but still capable of producing deep, dangerous avalanches.
See the video at for an example of how deep and energetically the snowpack can fail in an area with no signs of instability.:
http://www.youtube.com/user/sawtoothavalanche#p/a/u/0/qVEGb-8VhlQ
It’s an unusual snowpack and following the usual skin-tracks and descent strategies may not be enough to keep you out of trouble. Tracks on a slope do not indicate that it won't slide under your weight. The most dangerous conditions and most instability are presently occurring in the southern part of our advisory area, but the Sawtooth Mountains have more than their share of steep, rocky areas where it is possible to trigger deep, dangerous slides.
North Wood River Valley
 | The avalanche danger is estimated to be CONSIDERABLE on steep, shaded slopes in the North Wood River Valley. The layer of weak, faceted snow that’s now buried 2-3 feet deep continues to show signs of instability such as natural and triggered avalanches and in some locations, widespread collapsing. These indicators seem most common near Baker Creek, but a 2-3 foot deep, remotely triggered slide near Galena Summit yesterday shows that the danger of large, destructive avalanches exists throughout the region. Last night’s strong northwest winds will compound the danger by drifting snow near ridgelines. The greatest danger exists on recently wind-loaded slopes and in steep, rocky areas where the snowpack is shallower and it is easier to collapse the underlying weak layer and trigger an avalanche across a wider slope. Areas like this are most common on shady aspects but can be found at all elevations. South & Central Wood River Valley  | The avalanche danger in the South and Central Wood River Valley is estimated to be HIGH. Natural avalanches in this region yesterday evening demonstrate that very dangerous avalanche conditions persist. Last night’s strong winds have compounded the danger by drifting snow in gullies and near ridgelines. This windloading has added yet more weight to a very fragile weak layer that is buried 2-3 feet deep and very sensitive to the weight of a person. Travel on or beneath steep slopes is not recommended, even in valley bottoms and canyons. This includes out-of-bounds areas at Baldy. Human-triggered avalanches are very likely and natural avalanches are likely. |
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Wind speeds picked up late yesterday afternoon, particularly in the southern regions of our advisory area, and veered to the north-northwest. Baldy recorded averages over 20 mph overnight, and the station in the Soldier Mountains showed averages over 30 mph. The Titus station is showing much lower wind speeds, probably because it is shielded from winds out of the northwest.
The snow from the most recent storm is relatively light density and easily transported by such strong winds. The fresh wind slabs will be sensitive to the weight of a person or snowmachine today, and a danger in their own right today. Just as importantly, they’ve compounded the instability of the underlying persistent weak layer by rapidly adding load and creating cohesive surface layers that make it easier to trigger deep, destructive avalanches involving the faceted snow near the base of the snowpack. The slides last night on the east face of Della above Hailey indicate that this may be of particular concern in the south and central valleys. The northwesterly winds likely affected open slopes facing south-southeast, east and northeast in all regions, especially those near ridgelines. Be alert for snow that feels hollow or cakey, and for shooting cracks.
Current Conditions:
Temperatures remained cool yesterday, with most remote stations recording highs in the upper teens. Skies were partly cloudy in the southern part of our advisory area, but mostly cloudy to the north, where snow showers produced 0.2” of SWE and 2” of snow at most stations. Wind speeds increased and winds veered more northerly late yesterday afternoon; winds at Baldy have averaged over 20 mph since 5pm yesterday, and over 30 mph in the Soldier Mountains. Titus is shielded from northwest winds and is showing much lower average wind speeds. Under clear skies this morning, most valley and upper elevation stations are reporting temperatures in the mid to upper teens.
Mountain Weather Forecast:
A shortwave ridge passing overhead will bring mostly dry, cool weather today, followed by a weak system overnight. Winds seem to have started subsiding, and will continue to slow through the morning and shift back to the southwest. Today’s highs should be in the low 20s at upper elevations with partly cloudy skies. Tonight's weak system is forecast to bring more clouds, a brief increase in wind speeds, and a chance for 1-2 inches of snow, with lows in the mid teens at most elevations.
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