Helon and I took advantage of a warm sunny day to get up into Tuckerman. Our primary objectives were to look at the existing snowpack and get a handle on what today’s danger was, for anyone coming up later today, and for what the emerging heat wave might do to the snowpack.
For those few who came up today, they were rewarded with good stability in Right and Left Gully, but different conditions. Left Gully’s snow stayed cold and dry despite the +7C ambient air temperature. In one location, Helon found a thin 4F+ slab layer sitting on top of a loose graupel layer with very easy compression test results. Snow test results don’t always tell the whole story though. Helon’s impression was that the Moderate rating was appropriate. One of the skiers in the gully tested the slope with a finely executed faceplant, which is often a more realistic test of a slope’s stability than compression tests. (I’d name names, but the Harvard caretaker might not want his identity revealed.)
Right Gully had a much different environment than what was found in Left. Rather than cold dry snow, the surface layer was saturated with melted snow. At 11:45, the wet layer was 7cm deep. By 12:45, it was twice that or more. The loading that came in with yesterday’s 5cm snowfall didn’t create much new slab in Right, so my earlier concerns regarding stability of this layer were quickly erased as the sun baked the slabiness right out of the upper layer.
Standing in the middle of Right Gully for a long time, I began to look around at the terrain, and I realized that the snow I was standing on was probably 8-10′ lower than where it is in a typical winter. Trees whose tops are usually the only part visible were standing proud over my head. At the top of the gully, rocks that we see melt out sometime in early May have not even been buried this year. It really sunk home how poorly we’ve done for snowfall this year.
The 1F+ (hand hardness scale) slab in Right Gully was 100cm deep down to a hard, hard crust. The very top of the snowpack was wet snow from the heat and sun. Cooler snow was found down below, with a few centimeters of 1mm facets above the crust. I found it hard to really get a good look at the facets – the air temperature was +7C so as soon as I put some on a crystal card they began to melt. This facet layer gave two compression tests at CT21 and CT23. An extended column test did not propagate. I also got negative results with a shovel tilt test and shovel shear test on a suspected weak layer at 37cm down from the top. Generally speaking, these are good test results for the stability of the slope at the time the tests were done, but the facet layer is concerning for what might happen with further warming.
In the Sluice, Lip, and Chute, as well as the left side of the Center Bowl and in the hangfire, there is a good chance that the facet layer remains intact, and this might become reactive tomorrow or Thursday as the upper slab becomes wetter and wetter.
Here are some other pictures from the day:
I’m running out of time for this post now, so be sure to check tomorrow’s advisory for more information and stability ratings for the day.