Northern San Juan

Avalanche

Bill Nalli · Jan 20, 2020 · Northern San Juan

Weather

Clear skies in the morning transitioned into high clouds and overcast by 1pm. Calm wind.

Snowpack

Targeted north and northeast near and above treeline. These aspects have varying degrees of weak snow at the surface from fist hard near surface faceted crystals to one finger wind drifted dense slabs. As you approach treeline this combination becomes more pronounced and intertwined. 20 centimeters of settled snow sits on top of a one finger hard dense wind slab. This structure in itself is concerning as I experienced localized collapsing and cracking in wind exposed locations. but the most concerning part is what lies below the wind slab. Here the old snow surface prior to the last storm and also the last wind event is very weak. Fist hard 2 to 3 millimeter facets are not able to support much more of a load. Stability tests highlight this weakness with CT6 and ECTP 11 results. The strength of the wind slab compounds the problem as it will likely hold more of a load before it fails resulting in a much larger more dangerous avalanche. With low snow numbers in the forecast this problem will likely just linger for the next storm and wait for a bigger trigger.

Avalanche

Another D2 seen today that likely failed at the end of the storm on Friday January 17, 2020.