Bridger Teton Avalanche Center
WESTERN WYOMING AVALANCHE ADVISORY
Issued on Fri December 15, 2017 6:57 PM
Cloud cover over Western Wyoming increased throughout the day ahead of a low pressure trough approaching the region. Mountain temperatures rose into the low to mid 20s. Temperatures were inverted starting out in the morning before the valleys caught up to the higher elevations in the afternoon. Southwesterly to westerly ridgetop winds ranged from 10 to 20 miles per hour in most areas. Mount Coffin in the Southwest Trails forecast zone was the exception with hourly averages peaking in the mid-30s.
Just below the dusting of light density snowfall from the middle of the week, old snow surfaces in the mountains have a high degree of spatial variability. Stout crusts from late November were exposed by last week’s strong northwesterly winds on some windward slopes. This is most common in the Tetons where wind speeds were significantly higher. In leeward terrain, dense wind pack can be found under the recent snowfall, and dry settled powder in the beginning phases of faceting remains in areas sheltered from the wind. Surface hoar is common below and above the midweek snowfall, and sun crusts have also developed on steep, sunlit slopes.
FORECAST FOR Saturday, December 16, 2017
The chance for new snow will begin to increase in the early morning hours of Saturday as a low pressure trough and associated cold front move into the region. Light to moderate snowfall will continue through the day before tapering off by midnight. Overnight lows in the mountains will be in the mid-teens before rising to near 20 during the day. Westerly ridgetop winds will veer to the northwest at 15 to 25 miles per hour.
The general avalanche hazard above 9,000 feet is expected to be LOW Saturday morning. If significant snowfall materializes throughout the day, the hazard could increase to MODERATE in the afternoon as small pockets of wind slab develop near ridgelines. Monitor the buildup of these slabs, and avoid steep, avalanche prone slopes with obvious signs of wind loading, especially if these areas have high consequence terrain below. Under 9,000 feet, the chance for avalanche activity will quickly diminish with a drop in elevation.
TREND FOR Sunday, December 17, 2017 AND Monday, December 18, 2017
Mostly dry conditions and cooler temperatures are in store for Sunday and Monday. If new avalanche hazard does develop, it will slowly decline over the next couple of days.
For further information call 307-733-2664
To report an avalanche observation call 307-739-2607
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