Northern San Juan
SnowpackChris Bilbrey Bill Nalli · Apr 5, 2020 · Northern San Juan
Weather
Warm at low elevations and not much wind. In the alpine, SW wind was strong and gusty. Moderate wind loading continued most of the day but was erratic and not continually loading any one specific aspect.
Snowpack
It's a tale of two seasons in the mountains. The snowpack below about 10,500 feet continues to become moist, weaken, and is unsupportable in many locations. Northerly-facing slopes still harbor cold, dry snow mid-pack and near the ground with a moistening snow surface down 5 to 10 cm. This set up will be concerning with a rapid warmup at lower elevations or continued above freezing night's. All other aspects at similar elevations have evidence of vertical water movement down through the snowpack. As we climbed higher in elevation, we dug a snowpit on a southeast aspect at 11,600 feet. A moist, stiff slab rest above weak, moist facets (water present) and we observed the overlying slab fail in an Extended Column Test with 14 taps. Water present reduces strength of bonds between grains and this remains a concern until we see cooler temperatures and a return to nighttime freezes. In the alpine, we took a step back into winter. Moderate southwest winds were blowing and drifting recent snowfall into generally shallow but widespread wind slabs - textured snow surfaces and fat wind pillows below ridge tops were mostly soft but observed isolated cracking in deeper drifts. Recent snowfall and wind-drifted snow appeared to be bonding well to older snow below but a large natural avalanche failing in a heavily drifted part of the slope was enough reason to avoid steeper, wind-drifted areas that were northerly-facing. East and south-facing slopes in the alpine had a thin zipper crust on the surface and isolated terrain features had a soft, breakable wind-board/ skin on the surface with softer snow directly below.