Vail & Summit County
SnowpackAndrew McWilliams Max Strobeck · Apr 12, 2024 · Vail & Summit County
Weather
Clear skies, light winds, and plentiful sunshine. Temperatures rose to above freezing at 12,000 feet.
Snowpack
In the afternoon, we observed a snowpack that is in various stages of warming near treeline. A quick pit on a shaded, sheltered northerly slope close to 11,500 feet showed a cold and dry snowpack throughout. A pit on a north-facing slope close to the ridgeline a few hundred feet higher had moist snow in the upper 10cm of the snowpack and cold, dry snow below that to the ground. On an east-facing slope an hour later, there was moist to wet snow for the top 50cm of the snowpack resting on a 2-3cm melt-freeze crust that was becoming moist, the remaining snowpack was dry. Water has percolated down to at least the March 3 dust layer, but that was likely during a previous warmup. On a southerly slope, there was moist to wet snow near the surface resting on one of many stout melt-freeze crusts. A few of these crusts had ice lenses within them and there was evidence of water percolating close to ground level during previous warming cycles. By the time we were descending after close to 3 pm, the snow on northerly slopes was moist to wet and extended 10-20cm from the surface. Below 11,000 feet, the moist to wet snow was resting on a thick melt-freeze that was still supportable to skis and boots. There was dry snow below this crust. My biggest concern with the continued warm-up is north to east-facing slopes, where the snow is seeing its first major warming cycle that will extend more deeply into the snowpack, especially with a few nights of minimal to no freeze. In our pit on a north-facing near treeline slope, we still got a propagating result after blows from the shoulder in the February 2 surface hoar layer in an Extended Column Test (ECT). A non-propagating ECT in the east-facing pit suggests with continued wetting, the surface slab above the crust could sheet off on steep slopes. Southerly slopes could sheet wet snow off of crust layers as the wetting front descends, but with many crusts throughout the snowpack and water having moved through most of these layers, these slides would likely be small and less consequential than on slopes that are seeing water for the first time.