Avalanche: Cardiac Ridge

Observer Name
Observation Date
Friday, March 27, 2020
Avalanche Date
Friday, March 27, 2020
Salt Lake » Big Cottonwood Canyon » Cardiff Fork » Cardiac Ridge
Location Name or Route
Cardiac Ridge
We had a bit of a scare today putting in the skin track on cardiac ridge. My partner and I were ascending cardiac ridge and as we approached the ridgeline, I took one step forward and felt and heard the slope collapse and before we knew it, we were sliding. I deployed my airbag, but I was able to arrest on the bed surface after about 100ft. The crown broke several feet above me. My partner was at the last switchback under the rock band and lost his footing but quickly arrested. The slide continued down slope and a party of 4 who were likely 100-200 feet below us (pic 3) were able to quickly scoot out of the way. The slide took out parts of our uptrack and had a decent debris pile (pic 4) but never picked up a lot of momentum. It slid on a 2 cm suncrust. I could not appreciate any graupel on the bed surface. The more south facing aspect was heating up as we ascended and there were a few roller balls developing but once on east facing terrain the snow was not damp. Some red flags I ignored was a natural wind slab avalanche in steeper terrain south of thunderstruck coulior that we saw when skiing north Superior. It likely ran yesterday or early morning. There were also many point release sloughs along cardiac ridge but we assumed this wouldn't be problem on the relatively lower angle terrain we planned to ski. There were no telltale signs of wind loading, given the new snow, but it was likely a burried wind slab as it broke above me. Fortunate the party below us was able to get out of the way.
Other comments from Powderbird guides visiting the area
Hopefully you get a report from the party who triggered the slide, we did not see it happen but heard from others that it was human triggered. We ascended the debris and bed surface to check it out. Failed at NS/OS interface with facets above an old MF crust. Slab was 18" thick on average and F-4F hardness, with the exception of the bottom 4" or so, which was 1F hardness and likely provided the connectivity for the slab. On other slopes we did not find the same harder layer above the old snow surface and generally seemed like new snow was bonding pretty well on other ski runs.
Other comments fom another avalanche professional - I didn't pull out my loupe at the crown, but there were obvious facets above the old MF crust, so seems like in specific areas we might see a few more days of reactivity, really seems slab dependent for now,
pics Charlie Hussey