SITUATION:
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On Monday, Western Wyoming was under clear skies after morning valley fog dissipated. Temperatures were inverted with mountain highs west of the divide near 20 and highs in the teens in the valleys. Conditions were around 5 degrees cooler on the east side of the divide. Ridgetop winds were light and variable.
Snow surfaces transition from sun crusts with partially to fully degraded surface hoar on south facing slopes to well developed surface hoar resting on dry, loose snow on north facing aspects. In some areas, a buried surface hoar layer one to two feet in depth also persists. This layer failed on the sixth skier to cross an east-northeast facing slope at an elevation of 8,500 feet in the Snake River Range on Saturday. Weak, faceted snow persists at the base of the snowpack, and is the problem layer in the region’s avalanche fatalities this season. |
FORECAST FOR Tuesday February 09, 2010 :
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Expect mostly clear skies on Tuesday as an upper level ridge remains over the area. Inverted temperatures will persist with overnight lows in the mountains in the single digits and near -10 in the valleys. Tuesday’s highs will be in the mid teens to near 20 at the upper elevations and 5 to 10 degrees cooler down low. Ridgetop winds will back to the west at 5 to 10 miles per hour.
The general avalanche hazard is expected to be MODERATE in the Teton and Togwotee Pass areas, and CONSIDERABLE in the Greys River area where the snowpack remains more fragile. In steep avalanche terrain, the possibility persists for backcountry riders and skiers to trigger hard slab avalanches to the base of the snowpack. These slabs may fail after a slope has been crossed several times if a shallow weak zone is encountered. Larger loads, such as snowmobiles or groups of skiers, have a greater potential to cause failure of these weaknesses. In steep terrain, pockets of soft slab up to 18 inches in depth could also be triggered. These slides will become more susceptible to failure as the day warms.
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TREND FOR WEDNESDAY AND THURSDAY :
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Expect temperatures to warm, cloud cover to increase, and a chance of light flurries to develop as the ridge of high pressures shifts east Wednesday into Thursday.
Deep slab instabilities will persist. |
| EXTREME: Wide spread areas of unstable snow exist and avalanches are certain on some slopes. Backcountry travel should be avoided. |
| HIGH: Mostly unstable snow exists on a variety of aspects and slope angles. Natural avalanches are likely. Travel in avalanche terrain is not recommended. |
| CONSIDERABLE: Dangerous unstable slabs exist on steep terrain on certain aspects. Human triggered avalanches probable. Natural avalanches possible. |
| MODERATE: Areas of unstable snow exist. Human triggered avalanches are possible. Larger triggers may be necessary as the snowpack becomes more stable. Use caution. |
| LOW: Mostly stable snow exists. Avalanches are unlikely except in isolated pockets. |
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For further information call 307-733-2664  To report an avalanche observation call 307-739-2607 |
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Monday February 08, 2010 
