Special Warning: High Avalanche Danger
Dangerous conditions for most of all mountain ranges in NW Montana
by Stan Bones, USFS Glacier Country Avalanche Center
January 7, 2009
Special backcountry avalanche warning issued by the U.S. Forest Service Glacier Country Avalanche Center at 7:00 AM, Wednesday, January 7, 2009, for the Glacier Park and Flathead and Kootenai National Forest areas.
HAZARD ANALYSIS: Because of heavy new snowfall, we are currently rating the avalanche danger as HIGH over most all of the mountain ranges of Northwestern Montana.
Beginning Monday another strong Pacific weather system began moving into NW Montana. Like last Friday this storm also has the bulk of its focus in the East and West Cabinet Ranges on the Kootenai and in the mountains around the Flathead and Mission valleys. Snow water equivalents in those areas were in excess of 2.5" in 51 hours. Over half of that precipitation fell in the 15 hours from noon Tuesday to early Wednesday morning. Although the storm appears to be focused strongest in the southern half, no location across the region has escaped receiving significant amounts of new precipitation, falling either in the form of rain at the lower elevations or heavy, wet snow higher.
Accompanying the precip has been rising temperatures. Monday's readings generally started the day in the mid teens across the region. By Wednesday morning at approx. 3:00 am, air temps were registering near freezing or above at all of the mountain locations we regularly monitor remotely.
Because of heavy new snowfall, combined with a rapid rise in air temperature, unstable snow is likely on steep, open terrain in all of the mountainous areas of Northwestern Montana. Both natural and human triggered loose snow and slab avalanches are likely. Very dangerous avalanche conditions exist. Travel in avalanche terrain is not recommended. Extensive skill, experience, and local knowledge are essential to safely travel in the backcountry currently.
The weather forecast is for our region to remain in the influence of a Pacific storm track well into the weekend. The flow is expected to shift more NWerly Friday, bringing cooling temperatures and lowering snow levels. This cooling should produce a slight lessening of the avalanche danger Friday, however relatively speaking the danger will remain quite elevated into the weekend.
This advisory message will next be updated on Friday, January 9th, 2009.
AVALANCHE DANGER RATING KEY
LOW DANGER Snow is generally stable with only isolated areas of instability. Natural avalanches are very unlikely, while human triggered avalanches are unlikely. Backcountry travel is generally safe. Normal caution is advised.
MODERATE DANGER Unstable slab layers are possible on steep terrain. Natural avalanches are unlikely, while human triggered avalanches are possible. Backcountry travelers should use caution in steeper terrain on certain aspects.
CONSIDERABLE DANGER Unstable slab layers are probable on steep terrain. Natural avalanches are possible, while human triggered avalanches are probable. Backcountry travelers should be very cautious in steeper terrain. Be aware of potentially dangerous areas of unstable snow.
HIGH DANGER Unstable slab layers are likely on a variety of aspects and slope angles. Both natural and human triggered avalanches are likely. Travel in avalanche terrain is not recommended. Safest travel is on windward ridges or on lower angle slopes without steeper terrain above.
EXTREME DANGER Extremely unstable slab layers exist on most aspects and slope angles. Widespread natural and human triggered avalanches are certain. Large destructive avalanches are possible. Travel in avalanche terrain should be avoided and travel confined to low angle terrain well away from avalanche path runouts.
For more information contact Stan Bones, Flathead National Forest, U.S. Forest Service Glacier Country Avalanche Center, 650 Wolfpack way, Kalispell, MT 59901, Phone: 406-758-5284 phone, Fax: 406-758-5363.
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