Collapse city

CBAC 2020-21 Observations

Zone: Northwest Mountains

Location: Slate

Date of Observation: 12/16/2020

Name: Zach Guy


Subject: Collapse city

Aspect: North, North East

Elevation: N/BTL


Triggered a couple small persistent slabs remotely above a creek bed. Appeared to be a fresh D2 natural slab off of a westerly gulley of Gothic. Widespread activity from last weekend with numerous crowns 18″ thick spanning entire start zones where we traveled.


Weather: Ruby divide stayed in the clouds all day, with scattered skies elsewhere. Light snow at times. Light winds where we traveled, some drifting snow in the alpine.

Snowpack: Dozens of collapses, just about every open slope we came to. Some radiated hundreds of feet. With the exception of a few small pockets, every steep, shady pitch we came to had already slid over the weekend. Persistent slab structure is 2 feet thick at ridgeline and one foot at valley bottom. Stubborn cracking in isolated wind drifts on crossloaded south aspects up to one foot deep. Bed surfaces from the weekend cycle (friable melt freeze crusts a few inches thick over facets) are generally topped by 6” of low density snow.