Professional Observation

Observation Details

Signs of Unstable Snow

Key Points

We spent a short field day near June Mountain watching the first in a series of winter storms roll into the forecast area.

• We triggered small wind slab avalanches on test slopes near treeline. We found cornices to be sensitive to stomping. Wind and snowfall increased by midday. Moderate to intense blowing snow was common.
• The top 3 inches of snow was still wet this morning below treeline and we saw natural rollerballs and small wet loose avalanches from very steep terrain near trees and rocks. These were all below about 8100 feet. By about 11:30 am the surface began to refreeze as temps dropped and winds increased. New and drifted snow will fall on a melt-freeze crust at those lower elevations. The snow underneath the crust was still moist down about 6 inches below the surface; dry under that. The crust was spottier – confined only to terrain that usually gets sun – between 8100 feet and our high point of 9000 feet.
• We dug a hasty pit on a northeast aspect at 8900 feet where the total snow depth was 220 cm. We found all dry snow, mostly right-side-up, to pencil hard. That structure sat atop a knife-hard rain crust from the last rain event buried 155 cm deep. We got no propagation in our snowpack test.

More snow and wind are on the way overnight. Expect stability to deteriorate into tomorrow.