BC Zone Observation Report
Tuesday, January 22, 2019 at 12:00 AM
Vail & Summit County
Vail & Summit County
East Vail Backcountry.
Observed avalanches in East Vail routes known as Old Man's, Abraham's and Marvin's West or West Wall, per the VSP aerial photo maps. Observed from top of Benchmark and from the road above Marvin's West.
Sunny Sunday morning after significant storm Friday into Saturday. Aspects observed were north-east to east. 20+ degrees @ 10k feet by 11am.
New snow, 12+ inches, from Friday's (1/18) storm had formed into wind slabs on exposed slops due to moderate to heavy winds Friday into Sunday. Effects of wind and increased transport were obvious on hike to Benchmark, with some crossloading due to changing wind direction over the prior 36 hours. Noticeable increase in size of cornices throughout the area observed. A freezing mist arrived in the afternoon on Saturday, creating a thin ice crust on top of the snowpack, but had dried out overnight, leaving surface hoar. Snow was beginning to soften significantly on lower, sunnier aspects. Large roller balls led to larger snow entrainment on lower elevations due to poor bonding with old snow surface. Snow on northerly and shaded aspects remained cold and dry.
First slide observed from top of Benchmark, looking across to West Marvins in the West Wall area. 1st Slide: Appeared natural, and a day or two old, likely running sometime late Friday, 1/18, due to the few inches of new snow covering the debris. West Wall slide was approximately 300' wide and ran to the valley floor, approx 600 vertical feet. Slide appeared to have started above the prominent cliff band. Crown estimated at 1 foot deep and only included the new storm snow. No ski tracks observed around this slide. Slide was easily big enough to carry and bury a skier. This was enough evidence for us to stick with original plan of a more conservative ski route. Skied down west ridgeline on Mill Creek Rd above West Marvins, stopped, and looked back south at Abrahams and Old Man's/CDC. 2nd Slide: Observed a prior skier-triggered avalanche starting from the top of Benchmark, encompassing about two-thirds of the Abrahams slide path, from Tweeners over to start of trees on west side of Abrahams. Observed 10+ ski tracks at top of and on either side of slide and exiting from bottom of the path. Crown depth was again about 12-20" of recent storm snow. Slide was approximately 200' wide at top and ran approximately 400 vertical feet to the first bench. Slide was big enough to have swept a rider through the trees and cliffband around Mushroom rock and bury them on the bench. Slide must have occurred that morning and likely started from observed ski cuts at the top of the path. We observed what looked to be evidence of either a recovery or people investigating the debris pile based on ski tracks, foot prints and disturbances in the toe of the slide. 3rd Slide - Smaller, skier-triggered avalanche observed in the Old Man's path from this vantage, as well. Saw approximately 3 tracks heading from east entrance of Old Man's, dropping straight into the gut. Slide began mid-path from a ski cut, where the slope first rolls over steeply from first bench . Slide was approx 50-100 feet wide with 12-20" crown, running 100-200 vertical feet to next bench. Saw original ski tracks exiting slide from the bottom. Other ski tracks stayed to east side of slide path. Slide was from that morning, as well. We counted tracks in and out of the areas as best we could, and looked closely for any skiers or riders remaining in the area but saw none and departed. Other parties we saw on the way up were headed for watertank area and were accounted for at the bus stop upon exit. Fortunately, none of the slides stepped down into older snow. These events heighten my concern for increased avalanche activity in the area this week as loading from last night's storm and additional forecasted snow this week could push the snowpack past it's tipping point to produce some large, full-path slides, particularly in the paths that haven't seen recent activity. I expect to see poor bonding of new snow with the surface hoar we saw on Sunday morning, as well. Stay frosty out there.