Web Page: http://www.montanaweb.com/avalanche Telephone Hotlines: Flathead Valley & Outside Montana -- 406-257-8402 Toll-free Within Montana -- 1-800-526-5329 NW MONTANA GCAC BACKCOUNTRY AVALANCHE ADVISORY 03-14-00 This is Stan Bones with the Backcountry Avalanche Advisory for the Glacier Park and Flathead and Kootenai National Forest areas issued at 6:30 AM, Tuesday, March 14th, 2000, by Northwestern Montana's Glacier Country Avalanche Center. This advisory does not apply to developed ski areas and is brought to you in part by financial grants and support from: --The Sportsman and Ski Haus in both Kalispell and Whitefish --Winter Sports, Inc. on The Big Mountain --The Aero Inn, Highway 93 South, Kalispell --Truby's, 115 Central Avenue, Whitefish --The Izaak Walton Inn located at Essex --Kalispell Regional Medical Center --Rocky Mtn. Outfitter, 135 Main Street, Kalispell. --Burlington Northern Santa Fe Railroad --The Flathead Nordic Ski Patrol --The Montana Department of Fish, Wildlife, and Parks --The National Forest Foundation --The Users and Supporters of the Glacier Country Avalanche Center We would appreciate hearing from you. We thank Jim and Ted for their snow and avalanche information. You too can leave your snow, avalanche, and accident information after the beep on the telephone hotline. At any time you can go directly to the beep by pressing *. We can also be reached by computer at the e-mail address of gcac@digisys.net. ******************************************************* For today we are rating the avalanche danger as CONSIDERABLE on steep, recently wind loaded slopes above the elevation of 5500'. On windward and wind sheltered slopes above that elevation we are rating the avalanche danger as MODERATE. Below 5500' the avalanche danger is rated as LOW. ******************************************************* WEATHER ANALYSIS Since Friday the mountains of Northwestern Montana have been experiencing a cooling temperature trend and have been receiving varied amounts of new snowfall. Saturday was a big snow day for most of the mountains in the southern half of our region. Noisy Basin in the Swan near Bigfork, Moss Peak above Finley Point, and the North Fork Jocko near the southern end of the Missions each recorded at or near 1.5" of snow water equivalent Saturday. This translates into approx. 10" of medium density snow in 24 hours. The mountains in the Cabinet Range and those further west along the Idaho border received about 3/4 that amount, while our northern mountains in the Purcell, Whitefish, and Livingston Ranges only registered a couple of inches of new snow Friday through Sunday. Mountain temperatures Friday were generally averaging in the upper 20's and lower 30's. By Sunday and Monday these 24-hour averages had dropped slightly to around 25 F. The daytime mountain high temperatures at that time were between 25 and 32 F throughout our region. Winds have often been gusty during the period and this in combination with new snowfall has resulted in significant amounts of wind deposited snow in some locations. ******************************************************* SNOWPACK ANALYSIS Our backcountry tours over the weekend and on Monday were finding that the greatest instability currently existing in the snowpack is associated with the bond between the recent new snow and the previous old surface. The new snowfall was often accompanied by gusty and frequently variable winds. This has resulted in the new snowfall often being blown around and redeposited in wind slabs of varying strength. Digging deeper into the snow we are still finding buried weak layers associated with buried crusts, with buried ice layers, and with buried surface hoar layers. Recent mild temperatures are aiding in the strengthening and bonding of these buried weak layers, but they still persist on a variety of aspects at some locations. For the most part these weaknesses are within 30" or less of the surface. A backcountry party skiing in the Leigh Lake area of the Cabinet Mountain Wilderness reported being able to release the newly fallen snow Saturday by ski cutting. A group of ice climbers in the Many Glacier area reported watching a naturally released slab avalanche Sunday on a lee facing east slope of Grinnell Point. This slide reportedly ran out onto Josephine Lake. Also on Sunday a skiing party near Wahoo Ridge in the Rescue Creek drainage of the Middle Fork performed a rutschblock stability test and released a 6" slab of new snow when they stepped upon the test block. They confined the remainder of their day's travel to low angle slopes without steeper terrain above. ******************************************************* AVALANCHE - INSTABILITY ADVISORY We are currently rating the avalanche danger for today as CONSIDERABLE on steep, recently wind loaded slopes above the elevation of 5500'. Unstable wind deposited slab layers are probable on steep terrain there. Natural avalanches are possible, while human triggered avalanches are probable. Backcountry travelers should be very cautious on wind loaded slopes steeper than 35 degrees. Be aware of potentially dangerous areas of unstable snow. On windward and wind sheltered slopes above 5500' we are rating the avalanche danger as MODERATE. Recent new snowfall combined with persistent buried weak layers, means that unstable slab layers are possible on large, steep slopes there. Natural avalanches are unlikely, but human triggered avalanches are possible. Backcountry travelers should use caution on any open slope steeper than 35 degrees. Below 5500' we are rating the avalanche danger as LOW. Snow is generally stable there with only isolated areas of instability on large, steep, open faces. Natural avalanches are very unlikely, while human triggered avalanches are unlikely. Backcountry travel is generally safe below 5500'. Normal caution is advised. ******************************************************* WEATHER FORECAST & AVALANCHE OUTLOOK The weather forecast is for a fast moving cold front to move through Northwestern Montana Tuesday morning. Unstable air following the front should produce showery conditions through Wednesday. High pressure is expected to build Thursday and produce at least partial clearing during the day. The freezing level Tuesday is forecasted to begin the day near 4000' and drop to near 3500' by late day. Strong winds are expected to follow the frontal passage Tuesday afternoon and westerly winds of 25-35 MPH are likely with gusts of 40-50 MPH possible. These winds are forecasted to mix with 3-5" of new snowfall Tuesday to produce blizzard conditions at that time in the region's mountains. On Wednesday conditions should be mostly cloudy with scattered snow showers. Freezing level should vary between 2500-4000', while NW winds are expected to be around 20 MPH. 2-3" of additional snow is possible Wednesday. By Thursday drier air is expected over the region as warmer high pressure develops. Mountain daytime temps should climb well into the 30's F and new snowfall amounts should be less than 1" from scattered showers under partly cloudy skies. The new snowfall accompanied by very high winds on Tuesday is expected to maintain the avalanche danger at an elevated level on that day, if not push it even higher. Backcountry travelers need to be alert for rapidly changing conditions on Tuesday. ******************************************************************* This concludes the current avalanche advisory. The next regularly scheduled update will be issued by 11:00 AM, Friday, March 17th, 2000. The Avalanche Center now has its own webpage at www.montanaweb.com/avalanche. You can subscribe to receive this and other avalanche advisories by computer e-mail at www.csac.org. ******************************************************************* In an effort to improve our service to the public we are attempting to define the users of this advisory message. Please send us an e-mail message at gcac @digisys.net listing your backcountry interests. Are you a snowmobiler, snowboarder, mountaineer, snowshoer, or skier? This advisory best describes conditions at the time of its issuance. As time passes avalanche and snow conditions may change, sometimes quite rapidly. Elevation and geographic distinctions used are approximate and a transition zone between hazards exist. Because of the general nature of the advisory, each backcountry party will always need to make their own site and time specific avalanche hazard evaluations. Thank you again for your continuing support of Northwestern Montana's Glacier Country Avalanche Center. ************************************************************