This is Stan Bones with the backcountry avalanche advisory issued by the U.S. Forest Service Glacier Country Avalanche Center at 6:30 AM, Friday, December 21, 2007, for the Glacier Park and Flathead and Kootenai National Forest areas. HAZARD ANALYSIS Between 5,500' and 7,500' elevation the avalanche danger is currently rated CONSIDERABLE. Below 5,500' we're rating the avalanche danger LOW. These danger ratings expire at midnight, Friday, December 21st. The outlook is for the avalanche danger to remain elevated near current levels through the weekend. Because of the general nature of this advisory message, each backcountry party will always need to make their own time and site specific avalanche hazard evaluations. WEATHER ANALYSIS: Most all the mountain ranges of NW Montana received significant amounts of new snowfall in the period Tuesday through Thursday. The northern half of our region was the most blessed with three day new snow water equivalents commonly of 1.5- to 2.5-inches. This translates into 15 to 25 inches of new snowfall. The southern half of the region received only approx. half those amounts. Winds occasionally were gusty, predominately blowing from a westerly direction. Saturday through Monday's mountain air temperatues were mostly in the low 20's F across the region, while Tuesday through Thursday saw a slight warming into the upper 20's. SNOWPACK ANALYSIS: Our backcountry observations Thursday were on Allen Peak in the East Cabinets on the Kootenai, and in the Kimmerly Basin and Canyon Creek areas of the southern Whitefish Range, N of Whitefish. Our snowpit investigations in these two areas were finding the new snow was adding stress to a midpack layer of buried, weakly bonded faceted grains. In some areas up to an inch thick, this weak layer is typically found atop a much stronger buried melt-freeze ice layer. It was a combination of new snow loading, a substantial, buried and poorly bonded weak layer, all atop a strong, solid melt-freeze ice layer as a bed surface that produced the avalanche incident that seriously injured a 19-year old snowmobiler Wednesday morning in the Canyon Creek area of the southern Whitefish Range. While hi-marking a steep south facing slope he triggered a slab avalanche that mostly buried him and broke his femur when he impacted a tree approx. mid path. Continuing snow Wednesday night and early Thursday added to the stress equation and produced more extensive and widespread avalanching in the southern Whitefish Range Thursday morning. In the same area as Wednesday's incident, a lone snowmobiler became stuck in the new snow Thursday morning. While attempting to free the machine, a extensive natural avalanche released above him burying this newly accquired machine along with the jacket and helmet he had removed as he labored and the snowshovel he utilized to dig. The natural avalanches in the Canyon Creek and Kimmely Basin areas of the southern Whitefish Range on Thursday were releasing on steep slopes on all aspects, both in the open and in the trees. [21]http://www.glacieravalanche.org/incidents.cfm AVALANCHE - INSTABILITY DESCRIPTION: We're currently rating the avalanche danger between the elevations of 5,500 and 7,500' as CONSIDERABLE on steep slopes with significant amounts of newly deposited snow. Unstable slab layers are probable on steep terrain, both on open slopes and in the trees. 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 on all aspects. Below 5,500 ft. elevation we're rating the avalanche danger as LOW. Shallow snow there is often anchored by vegetation and terrain features and generally stable with only isolated areas of instability. Natural avalanches are very unlikely, while human triggered avalanches are unlikely. Backcountry travel is generally safe, but normal caution is still advised on any steep, open slope. WEATHER FORECAST & AVALANCHE OUTLOOK: The weather forecast is for a weak flow of cool, moist Pacific air to keep snow showers over NW Montana through the weekend. Friday may see a bit of drying, but Saturday and Sunday should be more active. Partial clearing Friday night could produce cold nighttime temperatures, retarding snowpack strengthening and even adding to the weakness of an already stressed snowcover. Backcountry travelers should be assessing snow stability this weekend on all steep slopes on all aspects. The next regularly scheduled update of this advisory message will be Friday, December 28th. We wish everyone a very Merry and safe Christmas.