Garden Wall Janitor-ing

Partnered with Going-to-the-Sun Road forecaster to assess avalanche hazards from this weekend's storm, and do some janitoring at the Garden Wall weather station (image). 

• Despite poor visibility, we noticed 3 large, fresh debris piles from natural avalanches that ran from upper elevations (avalanche tab). We couldn't see where they started. Guesstimated they ran Friday night or Saturday (May 6-7), during the weekend's high elevation rain event.
• 1-3 cm of ice on the solar panel at the Garden Wall weather station indicated that rain fell to at least 7300 feet during the storm. The rain-soaked snow had refrozen into a 2-5 cm thick, very hard crust between above about 6500 feet. Below this elevation, the crust was a similar thickness but soft and cracked around our skis. 
• Above the crust, we found 2-8" of fresh snow. This snow was dense, with rimed grains and graupel obvious. In hand pits (image), this snow was well bonded to the underlying crust, and generally only cohesive enough to form a slab where it had been stiffened by westerly winds. 
• We found a few soft drifts, and ski cuts on a steep test slope at about 6500' produced no cracking in a foot-thick drift. 
• The new snow was dry at all elevations in the morning, but had become moist below about 6000' by early afternoon. Turns on steep slopes produced roller balls (image), but these did not run far or entrain snow. 

Dry snow avalanche hazards seemed confined to steep, upper-elevation slopes where winds have drifted and stiffened the new snow. These could run fast on the hard crust below. Direct sun on the new snow at upper elevations seems likely to trigger widespread dry loose snow avalanches. On steep, continuous avalanche paths where these could run below about 6000 feet, it seems they could gouge into the moist snow below the soft, near-surface crust and produce more dangerous amounts of debris.