Twin Wildcat Lakes Avalanche Wednesday, February 1, 2012 Incident Report

Transcription

1 Twin Wildcat Lakes Avalanche Wednesday, February 1, 2012 Incident Report February 17, 2012 Location: (See Appendix A-1 Maps) Hungry Horse Ranger District Flathead National Forest -Region One Flathead County Montana Summary: 1 Male Backcountry Skier, Caught, Buried, Killed Mark Albee, age, 42, Bigfork, Montana Weather: (See Appendix A-2- Weather) This winter the northern portion of the Swan Range in NW Montana has been enduring a snow drought. Air temperatures have been mostly warmer than average, although four outbreaks of cold Canadian air did occur. Winds have generally been at, or slightly above average. In contrast to the normal wind pattern from the west to southwest, this season the area experienced more wind from the northwest. Initially October s precipitation was well above average. Warm temperatures however, dictated that moisture was in the form of rain and not snow. It wasn t until air temperatures cooled near the beginning of November that snowfall began to accumulate. The rate of snowfall for the month of November approximated normal, but the first half of December was a flat line. By the 15 th of December, the Noisy Basin Snotel (located two air miles almost due south of the avalanche site) was only registering 5.5-inches of snow water equivalent versus the normal 15.0-inches, only 37% of average. On the Monday prior to the incident on Wednesday, , a moderately strong Pacific storm brought new snowfall to the area. Noisy Basin Snotel registered a 1.7-inch increase in snow water equivalent over the 24-hrs. of There was no increase recorded on Tuesday. On Wednesday, the day of the incident, another 0.9-inch of SWE was recorded. There are no sites that record wind data for the region. However knowing the storm patterns for the Swan Crest, it is safe to assume that at least some wind deposit of newly fallen snow was occurring Monday through Wednesday. The Swan Crest lies nearly perpendicular to the prevailing westerly winds. This results in significant orographic precipitation and wind scour and fetch on the westerly, windward aspects of peaks and ridges and wind loading onto easterly, leeward aspects. Huge cornices regularly grow at many ridge locations along the Swan Crest. Page 1 of 19

2 Avalanche Condition (See Appendix A-3 Avalanche Advisory) On the day before the incident, Flathead National Forest issued its regular Tuesday backcountry avalanche advisory rating the avalanche danger as considerable between the elevations of 5,500 and 7,500 feet on all mountain ranges. Of special concern was steep, open, wind loaded slopes and gullies. Backcountry travelers were advised that natural avalanches were possible, while human triggered avalanches were likely. The size and distribution of avalanches ranged from small in many locations, large in specific areas, and very large in isolated areas. The highest concerns were with the newly precipitated and wind loaded snow. Skier Group Information: (See Appendix A-1 Maps) The party was made of two brothers, Mark and Iain Albee. Their plan for the day was to do a circuit ski tour over and along the crest of the Swan Range and return. They began by taking snowmobiles up the Jewel Basin Road, NFSR No. 5392, to the vicinity of the Jewel Basin trailhead, parking area, and cabin in Noisy Basin. From there they climbed on skis to the east into the Picnic Lakes Notch where Trail #397 meets the Alpine #7. Climbing the south aspect from that pass they gained the crest of the Swan Range and then skied north toward the Twin Lakes Notch. Above Twin Lakes on Peak 7164 they descended the easterly aspect, wrapping into the notch at the intersection of Trails #7, #8, and #721. Again climbing the southerly aspect they continued north on the crest to Peak 7110, approximately half way between Twin and Wildcat Lakes. They arrived at the summit of the peak around noon. Peering over the edge to the east, Iain reports that he didn t feel they were positioned on an overhanging cornice. He felt they were well supported by the east facing slope below. They gazed around as the clouds were beginning to break and snapped a few photographs. With his climbing skins still on Iain locked the heels of his AT bindings around 12:15 pm and began a gentle descent toward the small rimed trees on the west face. Their plan was to ski down that face into the bottom of the Noisy Creek drainage near the 4,600 ft. elevation, then climb back to the south, up to the Jewel Basin Road and the awaiting snowmobiles. Iain reports that he had moved only feet when he heard a pop, saw the snow crack and felt the snow settle under his skis, rocking him back on his heels. Glancing backwards to his right he saw the ridge snow breaking into blocks and the tails of his skis hanging off in air. Turning then and looking back to his left where Mark should have been, he saw nothing. After a few moments to gather his wits, Iain returned to the edge and peered over to see only a void. He called down the slope hoping to hear Mark reply. After yelling a few expletives and hearing no sounds he assessed how to descend the slope. He felt that with the condition of the snow, the steep slope, and being alone, it was not safe to directly ski any of the east aspect. He had very little opportunity to even get off the ridge. He backtracked along the ridge to the position near Twin Lakes where he could more reasonably descend. Once he gained the flat where the Alpine #7 trail is located, he generally followed it to the base of the avalanche debris. The trip from the peak to the south edge of the debris took approximately 40 minutes. By this time Iain felt certain that Mark was deceased. It was a very large avalanche with a steep drop over rocks on the upper half. A hasty beacon search at this point yielded no signals. Iain had left his cell phone in the vehicle at the bottom of the mountain. Mark had been carrying the only cell phone that day. Iain felt his only recourse was to return to the snowmobiles and then to the vehicle to call for help. From the toe of the avalanche he skied back to the south dropping down onto the flats of the Jewel Basin Lakes. From the flat north of Black Lake he Page 2 of 19

3 climbed to the Picnic Lakes Notch, skied the west aspect back to the trailhead and waiting snowmobile, and then rode down the road to the vehicle. At approximately 1430 hrs he called via cell phone family members and 911. Avalanche Characteristics: Tony Willits, Andrew Johnson, and Stan Bones, Flathead National Forest, visited the scene at approx hours, Thursday, February 2, the day following the avalanche release. They arrived on scene just after the helicopter had lifted off with the body and the North Valley SAR and FS snowmobile team had departed. Throughout the ski to the site they observed no obvious signs of remaining avalanche instability. Tony Willits and Joy Sather revisited the avalanche runout zone again on Monday, February 6. Central aspect of the avalanche was N35E (NNE), map measured Average slope angle at the highest portion of the crown is unknown, crown could not be safely accessed Elevation at highest portion of the crown fracture was approx. 7,110 ft, map measured Deposition was onto two bench levels separated in elevation Elevation at toe of the runout was approx. 6,465 ft on southern bench and 6,330 ft on northern bench, map measured Maximum total vertical fall was approx. 780 ft, map measured Total slope distance was approx. 1,475 ft, map measured Total horizontal length of slide was approx. 1,275 ft, map measured Alpha angle was approx degrees, calculated Total avalanche width was initially approx. 140 ft at the ridge top, increasing to approx. 1,100 ft at the very bottom, map measured Avalanche reportedly released at approx hours, Wednesday, February 1, 2012 Avalanche type was HS/SS, hard and soft slab combination Avalanche trigger was ACu, cornice fall unintentionally triggered by human Lineal width of crown fall was approx. 140 ft, map measured Weight of collapsing cornice was probably at or in excess of 35 tons, estimated and calculated Destructive force was D3, could bury and destroy a car, damage a truck, destroy a wood frame house, or break a few trees Size relative to the path was R4, large Avalanche released within the old snow Avalanche was a chain reaction, stepped release: o On the highest portion of the slide, the cornice fall appears to have triggered a slab release primarily on exposed rock and within a basal layer of weakly bonded, old, faceted grains. This layer developed in many locations around the region in November and December at a time when the snowpack was shallow and air temperatures were cold. The layer was involved in several natural and triggered avalanches in late December. It has been most active over exposed rock and is one we continue to find and monitor in locations having a shallow snow cover. The upper portion of this particular avalanche path would have been scoured by east winds during the cold Canadian air events. o As the moving snow mass transitioned from the exposed rock onto the moderately buried mid slope, the bed surface appears to have shifted to a weak Page 3 of 19

4 layer higher in the snow cover, most likely a buried surface hoar layer. The avalanche also began releasing across the slope further to the north, crossing over other rock outcrops and reaching into adjoining swales. This exponentially increased the amount of involved snow. o Toward the lower third of the avalanche, the bed surface stepped down again substantially deeper to a melt-freeze ice layer near the ground. At some locations along the southern flank, where the avalanche was confined by a rock wall spur rib, this ice layer was covered by more than 10 feet of mostly wind deposited snow. o Because of safety concerns only the lower portions of the avalanche were investigated. No actual shear tests were conducted Liquid content was dry Failing slab thickness and crown heights were highly variable, ranging from approx. 12-inches to over 10 feet, measured and estimated When found and uncovered Mark s body was in an upright position. One ski was still attached. The other was found broken nearby in the excavation. In the avalanche he had fallen approx. 500 vertical feet. The avalanche debris was quite hard, making digging difficult. Lightweight plastic shovels were reported not to be up to the digging task. Emergency Response: Flathead County Sheriff s Office reports: Initial Call Information Initial call came in at 1436 hours from a 911 call from brother Ian. Phone contact made with Ian who stated his brother and him were standing on a ridge line south of Wildcat Lake when a cornice broke off and his brother was taken down the hill in an avalanche. Ian stated brother had an avalanche beacon, and was an experienced skier. He stated the avalanche was large and he did not see any debris. Wednesday s Initial Search ALERT helicopter paged, but advised weather did not allow them to access area. North Valley SAR paged for snowmobile deployment from South Fork, Flathead SAR paged to Jewel Basin to transport Nordic Ski Patrol. Nordic paged to ski in from Camp Misery. USFS advised and a request for LEO s with snow machines, and advisement on avalanche conditions. By dark conditions continued to remain snowy, and foggy creating difficulty to visually assess scene and travel routes. Snowmobile team and Nordic were unable to access avalanche site. During the night operation plans were made for the operational period starting at 8 a.m. Helicopter operations, along with better communications were covered to increase searcher safety. Fresh crews were also arranged due to unknown weather conditions. Thursday s Recovery Efforts North Valley/ USFS snowmobile team deployed to attempt access through drainage below Wildcat Lake. Were ultimately successful. Nordic Ski Patrol attempted to gain access through travel route through bottom of Jewel Basin, Twin Lakes, and then avalanche site. Was next team to arrive on avalanche site if search would have continued. Page 4 of 19

5 Repeater was placed on top of paraglider point which helped communications, along with a bank of radios from OES preprogramming. Helicopter was able to land in area of Wildcat Lake, but was grounded due to lowering cloud bank. Snowmobiles from North Valley and USFS were able to get to location and begin beacon search. Subject was located five feet down in head up position. Was dug out and transported by helicopter once cloud levels raised. Other teams were turned back due to reports of areas of unstable snow in search area. Official cause of death was asphyxiation. Lessons Learned / Reaffirmed: Cornices always demand respect. They pose a significant hazard potential to backcountry travelers. Because of a north-south orientation, most of our mountain ranges are perpendicular to the prevailing westerly winds. Consequently huge cornices often grow at many locations. Perla and Martinelli in the Forest Service Avalanche Handbook, July 1976, state: Maintain communication. This applies at all levels: o among your touring/riding group o with the home front, family, and friends as best you can while in the backcountry o in rescue/recovery operations between incident command and field units and within and between field units. Cell phone calls are frequently possible from our mountain ridges, particularly around the Flathead Valley and along the Continental Divide. Although Mark s death likely would not have changed, in this instance a phone call from Iain at the time of the cornice Page 5 of 19

6 collapse may have sped the recovery effort. On this day he had left his phone in the vehicle at the bottom of the mountain, thinking, there is very little chance of service and besides Mark has his. Keep your wits and always exercise caution. Iain voiced this. After the avalanche left him alone, he felt it imperative that he exercise caution and not fall victim to another incident. This applies also to rescue and recovery efforts. Risk needs to be reduced to a manageable level by reducing in unison the probability, exposure, and consequence of actions and subsequent incidents. Appreciation: We very much appreciate the assistance of Iain Albee, Flathead County Sheriff s Office, Forest Service Law Enforcement, and Craig Moore of GlacierWorld.com who shared with us information and photographs that make this report possible. We hold Iain Albee, both Mark and Iain s families, and their friends in our prayers during this difficult time of loss. Stan Bones, Flathead National Forest February 17, 2012 Page 6 of 19

7 Appendix A-1 Maps Twin - Wildcat Lakes Avalanche Vicinity Map Kalispell Twin - Wildcat Lakes Avalanche Site Bigfork Page 7 of 19

8 Approximated Albee Brothers Routes Cornice Fall & Resulting Avalanche Snowmobile Parking Legend Snowmobile Access Ski Ascent Planned Ski Descent & Return Iain s Ski Descent & Return Page 8 of 19

9 Wednesday s Approximated Rescue Attempt Access Map Twin - Wildcat Lakes Avalanche Site Legend Motor Vehicle Access Flathead Nordic Ski Access Snowmobile Access, Flathead SAR Snowmobile Access, North Valley SAR & FS. Noisy Basin Snotel Incident Command Post Page 9 of 19

10 Thursday s Approximated Recovery Access Map Twin - Wildcat Lakes Avalanche Site Legend Motor Vehicle Access USFS Ski Access Snowmobile Access, Flathead SAR Snowmobile Access, North Valley SAR & FS. Noisy Basin Snotel Site Incident Command Post Page 10 of 19

11 Appendix A-2 Weather Period of Record Average Snow Water Equivalent Accumulation Seasonal Total Precipitation Accumulation * * * * Period of Record Average Total Precipitation Accumulation Seasonal Snow Water Equivalent Accumulation *Cold Canadian Air Events Noisy Basin Snotel - elev ft. Snow Water Equivalent Year-to-Date Precipitation Date Current Average Pct of Current Average Pct of (in) (in) Avg (in) (in) Avg October 15, * November 1, * November 15, December 1, December 15, January 1, January 15, February 1, * = Analysis may not provide a valid measure of conditions. Page 11 of 19

12 Appendix A-3 Avalanche Advisory Avalanche advisory does not apply to developed ski areas Issue Date: 8:00 AM, Tuesday, January 31, 2012 Valid Until: Midnight, Tuesday, January 31, 2012 Next Update: Friday, February 3, 2012 Issued by: Tony Willits This advisory is a product of the US Forest Service, US Dept. of Agriculture. Along with other snow and avalanche information, it is originally posted at An audio summary is available via telephone at All Mountain Ranges 7,500 ft. elevation 5,500 ft. Avalanche Danger Summary 3 -Considerable : 5,500 to 7,500 ft. elevation, especially on steep, open, wind loaded slopes and gullies 2 - Mod : below 5,500 AVALANCHE INSTABILITY DESCRIPTION Danger Level Confidence Travel Advice Likelihood of Avalanches Avalanche Size & Distribution 3 CONSIDERABLE All Mountain Ranges - 5,500 to 7,500 ft. elevation Fair Dangerous avalanche conditions exist, particularly on steep, open slopes especially associated with recent wind loading Careful snowpack evaluation, cautious route finding, and conservative decisionmaking essential Natural avalanches possible Human triggered avalanches likely Small avalanches in many locations or Large avalanches in specific areas or Very large avalanches in isolated areas Page 12 of 19

13 AVALANCHE INSTABILITY DESCRIPTION Danger Level Confidence Travel Advice Likelihood of Avalanches Avalanche Size & Distribution All Mountain Ranges below 5,500 ft. elevation 2 - MODERATE Fair Heightened avalanche conditions exist on steep, open slopes and gullies Evaluate snow and terrain carefully Identify features of concern Natural avalanche unlikely Human triggered avalanches possible Small avalanches in specific areas or Larger avalanches in isolated areas 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. 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 transition zones between hazards exist. Recent Mountain Weather Summary Precipitation Friday Tuesday (0300) ---A cold moist west flow transitioned from Saturday into warm moist flow on Sunday. The warm moist flow of Pacific air brought moisture, relatively mild temperatures, and wind to the region. o 0300 Saturday through 0300 Sunday;.4 to.7 inches of snow water equivalent (SWE) was received across the region o Sunday through Monday, warm flow accompanied by moisture created an inverted snow pack with snow fall amounts near 2.0 inches of SWE during this period o Rain at lower elevations on Monday, which seemed to be at approximately 5000 feet in the Northern Swan. Temperature Wind Temperatures warmed by 15 degrees from Saturday to Sunday, with temperatures at or near freezing from Sunday through Monday. Winds were strong on Saturday afternoon with snow being transported onto lee slopes. Sunday s winds were moderate out of the SW at ridge tops. Field Observation Locations Monday, Observer Report Locations Meadow Peak, 34 air miles SE of Libby Jewell Basin NE of Big Fork in Northern Swan Range None received Avalanches Observed No natural releases were observed on Monday. Visibility of surrounding terrain was limited due low cloud ceiling Page 13 of 19

14 Instability Concern / Avalanche Problem Level of Concern Most Less Least New Storm or Near Surface Snow Wind Loading Recent or Persistent Buried Weak Layer Spring Wet Snow or Melt-Freeze Moderate to heavy amounts of new snowfall Friday thru Monday on all ranges Snow that fell on Saturday and on Friday was colder and less dense than the warm more dense and heavier snow that fell on Sunday and Monday. This created an inverted condition within the surface layers with heavier snow overlying weaker snow below. Strong SW-W winds Saturday PM produced wind transport and redeposit of snow in saddles, along ridges, and over peaks Sunday winds were moderate out of the SW Weakness is being found between the new precipitated or wind deposit snow and buried old snow surface These weak layers reacting with easy force in shear tests Currently buried in the upper third by recent new snowfall Not applicable Rain-on-Snow At lower elevations Loose Snow Other Concerns Weather Forecast Summary Precipitation Temperature Wind Current NWS Backcountry Forecast Westerly flow will continue over our region directing Pacific moisture into the region on Tuesday. On Wednesday another system will enter our region bringing localized moderate to heavy accumulations in the mountains. Thursday will see drying conditions as high pressure builds over the region. 9 to 12 inches of new snow is expected from Tuesday AM through Wednesday night. Temperatures will continue to be slightly above normal for this time of the year. Temperatures on Tuesday should be near freezing and cooling only a bit beyond that time into the mid twenties. Moderate at 17 to 18 MPH, from the SW on Tuesday, AM & PM, and moderate again on Wednesday, AM & PM, out of the west. Avalanche Outlook Trend Concern Comment The avalanche danger should remain at current levels through Wednesday. A moderating effect should occur to the avalanche danger during Thursday, as a ridge of high pressure begins to build over the region. Recently wind loaded snow onto lee slopes, especially with special concern directed to E, NE, N, NW convex rolls below ridge tops. Continued moderate to heavy snow fall, adding loading to an already inverted surface snow pack condition. Always carry and know how to use avalanche safety equipment Check out the site specific snow stability before jumping in or on Events: On Tuesday night an avalanche awareness class will be held at the Eureka High School from 6 to 9 PM. Page 14 of 19

15 Appendix A-4 Photographs Approximate location of Mark s burial Page 15 of 19

16 Approximate location of Mark Albee at time of cornice collapse Page 16 of 19

17 Collapsed cornice section Page 17 of 19

18 Deep section of flank fracture near base of south confining rock wall USFS photo View from Mark s burial site upslope, showing collapsed cornice and path USFS photo Page 18 of 19

19 Initial searching by the snowmobile recovery party focused upon this lower, northern bench. It was only after the fog began to lift that the upper, southern bench in the background became visible and the full extent of the avalanche was known. Searching on the upper bench quickly produced a transceiver signal. Flathead Co. Sheriff s Office Photo - Flathead Co. Sheriff s Office Photo Page 19 of 19