NW MONTANA GCAC BACKCOUNTRY AVALANCHE ADVISORY 1-27-98 This is Stan Bones with the Backcountry Avalanche Advisory for the Glacier Park and Flathead and Kootenai National Forest areas issued at 11:00 AM, Tuesday, January 27th, 1998, 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 from: --The Aero Inn, Highway 93 South, Kalispell --The Izaak Walton Inn located at Essex --Rocky Mtn. Outfitter, 135 Main Street, Kalispell. --The Runner-Up Sports Consignment Shop in downtown Whitefish --Ski Mountain Sports, 200 Wisconsin Avenue, Whitefish --Winter Sports, Inc. on The Big Mountain --Zauner's Recreation Center on Meridian and Center in Kalispell --Burlington Northern Santa Fe Railroad --The Flathead Nordic Ski Patrol --Kalispell Regional Medical Center --The Montana Department of Fish, Wildlife, and Parks --The National Forest Foundation --The Users and Supporters of the Glacier Country Avalanche Center For those of you accessing this message from within the Flathead Valley we remind you of the cheaper local access number of 257-8402. Please use only that number. We would appreciate hearing from you. After the beep please leave your suggestions for improvement of this message and your snow, avalanche, and accident observations. Names need not be given. At any time you can go directly to the beep by pressing *. If you need to talk with a real person please leave your name and phone number and we'll be in touch. In your message please include the time and date of your call. By computer we can be reached at the e-mail address of gcac@digisys.net. ******************************************************* In the southern portions of our region that are receiving warming temperatures and locally heavy snowfall, we are currently rating the avalanche danger as HIGH above 5500' in elevation. In the northern half above 5500' where warming has been occurring but conditions have remained more dry, we rate the avalanche danger as CONSIDERABLE. Below the elevation of 5500' we rate the danger as MODERATE. ******************************************************* WEATHER & SNOWPACK ANALYSIS The electronic sensors that we regularly monitor are indicating that since last Friday the mountains of our region have picked up variable amounts of new snowfall. Over that period they received at least 0.5-1.0" snow water equivalent. This would translate to approx. 6-12" of new snowfall over the four days. The exceptions were Jocko at the southern end of the Mission Range and Flattop in the interior of Glacier Park which picked up almost twice that amount of snow. Bear Mtn on the Montana-Idaho border SW of Libby received even more at 3" SWE, translating into 2.5-3' of new snow. Mountain temperatures Friday through Sunday were generally near the freezing level for daytime highs and mostly cooling at least into the mid 20's at night. Some locations showed signs Sunday night of clearing and this allowed the temps to drop even lower into the mid teens. Mountain temperatures Monday night and Tuesday morning had generally warmed to near or above freezing. Winds west of the Continental Divide for the period of Friday to Tuesday morning appear to have mostly been light. The areas along and east of the Divide are continuing to receive their typical winds. Winds at St Mary Monday were SW mostly at 15 MPH with gusts of 35-45. Snow scour and transport was reported Monday to be a major factor in snow instability in the Marias Pass area. A look at the radar Tuesday morning showed that the southern portion of our region was receiving light to moderate to locally heavy snowfall. This disturbance was tracking through Sanders, Lake, and SE Flathead counties, on to the east front south of Marias Pass. It generally appears that those areas north of a line from Libby to Kalispell, onto Marias were mostly dry overnight. A surface low pressure center is situated east of Spokane and producing moderate to heavy rain in that area. It is showing signs of moving in our direction. Snowpit investigations and backcountry tours over the the weekend and Monday continued to find weaknesses in our region's snowpack. This was well exhibited by the avalanche accident Saturday at Inspiration Pass in the Swan Range that resulted in the death of one snowmobiler. We have reports of another human-triggered slide on Saturday also catching a party of backcountry skiers in the southern Whitefish Range. No one was seriously involved in that small avalanche. Our region's snowpack continues to lag below normal depths. Recent snowfalls, sometimes accompanied by wind and sandwiched in between short lived dry periods, are creating variable layering in the upper portions of the pack. Clearing conditions Sunday night were producing thin surface hoar deposits are the snow surface in some locations. Temperature that have warmed from below to near or above freezing Monday night and Tuesday morning are causing stresses and weaknesses to develop. Locally heavy snowfall of wet or warm dense snow is also causing considerable loading in the southern portions of our region. The weakly bonded angular grains that developed at the base of the snow in November and early December continue to persist at various locations over all our region. Throw in some weaknesses associate with buried graupel and low density needle snow layers and we come up with a real mess.of uncertainty and discomfort with the current state of the snow's stability. ******************************************************* AVALANCHE - INSTABILITY ADVISORY In the southern portions of our region we are currently rating the avalanche danger as HIGH above 5500' in elevation. Because of locally heavy dense new snowfall Tuesday morning upon a snowpack with considerable weaknesses, 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. In the north portions of our region above 5500' in elevation we are currently rating the avalanche danger as CONSIDERABLE. Because of rapidly warming temperatures unstable slab layers are probable on slopes steeper than approx. 35 degrees. Natural avalanches are possible, while human triggered avalanches are probable. Backcountry travelers should be very cautious in steeper terrain above 5500'. Be aware of potentially dangerous areas of unstable snow. Below 5500' over our whole region we are rating the avalanche danger as MODERATE. Because of significant warming often accompanied by rain unstable slab layers are possible on slopes steeper than 35 degrees. Natural avalanches are unlikely, while human triggered avalanches are possible. Backcountry travelers should use caution in steeper terrain. ******************************************************* WEATHER FORECAST & AVALANCHE OUTLOOK The weather appears to be the key to our current state of avalanche danger and snow instability. The disturbance that is moving through the southern portions of our region Tuesday morning appears to have more dynamics that was originally forecasted. It is showing signs that it may expand even into the northern half of our area. Stay alert for rapidly changing conditions Tuesday. The weather forecast is for a ridge of high pressure and drier air to move over Northwestern Montana beginning Wednesday. A few weak disturbances could slide through this ridge and bring isolated light snow and rain showers. Late Thursday a strong trough of low pressure has the potential to bring our region significant new snowfall and increasing avalanche danger and snow instability again. The key now we believe is to keep ever alert and vigil. We could see rapidly changing conditions over our entire region and significant avalanche activity Tuesday and possible on into the week. Remember that avalanche accidents are generally no accident. These slides are often triggered by the victims or someone else in their party. Stay alert for signs of snow instability, work the terrain to your advantage to minimize the risk, and be prepared and equipped for the worst when you make the wrong call. ******************************************************************* This concludes the current avalanche advisory. The next regularly scheduled update will be issued at 11:00 AM, Friday, January 30th, 1998. For those of you with access to the World Wide Web, check out this and other avalanche advisories at www.csac.org and at www.avalanche.org. ******************************************************************* In an effort to improve our service to the public we are attempting to define the users of this advisory message. Please stay on the line until after the beep and leave a message listing your backcountry interests. Are you a snowmobiler, snowboarder, mountaineer, snowshoer, or skier? Also let us know if you are calling from within the Flathead access area or outside and using the 1-800 number. 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. For current information on snow conditions stop at the Glacier Park Ranger Station at your point of entry, or call a U.S. Forest Service Office. Thank you for your support of Northwestern Montana's Glacier Country Avalanche Center. ************************************************************