Northern San Juan
AvalancheJeff Davis · Mar 13, 2020 · Northern San Juan
Weather
Squally spring storm that stated around 4am and continues into this evening. Today's events consisted of periods of heavy snow and intense wind-diffing followed by fog and sucker holes of blue sky. This storm was out of the south and southwest and it is assumed that the heaviest precipitation and snow accumulations are on Molas and Coal Bank Passes.
Snowpack
3"-4" of new snow was measured at our highway snow study plots in the morning. During the day this number doubled if not more. When traveling in the field it was obvious that the closer you traveled to treeline the more snow you would find. Estimated totals today, 6"-8" at roadside and 12"- 14" near and above treeline. South and southwest winds were strong enough to move the snow onto leeward slopes and other skiers reported drifts up to 24" and cracking in the new snow. The new snow is falling on a firm melt-freeze crust at lower elevations and hard wind-slabs in the alpine. The snowpack was undergoing the spring transition prior to the storm and though the surface refrozen it appears wet snow persists under the crust.
Avalanche
Two small Storm Slab avalanches hit the highway around 1:00 pm. The avalanches were triggered by strong wind-loading and broke as a slab. The avalanches failed at the new and old snow interface.