Accident: First Cornice

PATRICK KESSLER

Salt Lake » Snake Creek » Lavina Creek » First Cornice

First Cornice

9,500'

Northeast

Unknown

Snowmobiler

Remotely Triggered

Hard Slab

Wind Drifted Snow

Facets

5'

800'

1

1

1

"FOLLOWING AN AVALANCHE PRO 1 PRACTICE SESSION IN A SAFE LOWER BOWL THE GROUP OF THREE WAS HEAD UP TO THE TOP OF THE CORNICE ALONG AN ESTABLISHED SKIN TRACK ON A LOWER ANGLE APPROACH. WITH THE SNOWPACK AND SNOWFALL ACCUMULATION, AND THE AVALANCHE DANGER SCALE RATING HIGHER IN SURROUNDING AREAS, WE OPTED TO JUST STAY MISSION FOCUSED AND STEP OUT VERY CAUTIOUSLY. OUR RIDER ETHICS FOR THE DAY WERE UNSPOKEN, BUT THE CREW WAS TAKING IT ONE AT A TIME IN CRITICAL SPOTS AS TO WATCH EACH OTHER PROGRESS SAFE AS POSSIBLE. ONE RIDER WENT, THE NEXT RIDER WENT BUT CUT SLIGHT RIGHT ON THE ASCENT AND I (THIRD RIDER) WENT.

AS I CLIMBED THE TRAIL ALONG THE FORESTED LINE I CUT ACROSS THE CRITICAL AREA. THIS I WHEN THE ENTIRETY OF THE SLOPE TRIGGERED, AS FAST AS I WAS SWEPT UP, I DO NOT BELIEVE THAT I WAS THE SOURCE OF THE TRIGGER BUT POSSIBLY THE SECOND RIDER CUTTING RIGHT. THERE IS NO BLAME TO PASS FROM MY ACCOUNT. EITHER WAY, IF I TRIGGERED IT FROM BELOW THE PROPAGATION TRAVELED 1KM TO THE ACTUAL STAUNCH WALL, IF IT WAS TRIGGER FROM THE SLIGHT RIGHT ON ASCENT, IT WAS PROPAGATED FROM NEARLY 800-1000M AWAY. THE VISIBILITY WAS MINIMAL BUT WE COULD SEE A 2.5M WALL WHERE THE SNOW BROKE, WHERE WE SAY NEARLY NO TO 10CM LIP AT THE CORNICE BEFOREHAND. I WAS BURIED 30M DOWNHILL FROM MY SNOWMOBILE, LUCKILY ON THE FLANK AND ONLY SUBSURFACE.

THE SNOWMOBILE WAS BURIED NEARLY STRAIGHT UP AND DOWN TO A DEPTH OF 2M, AS THE ONLY VISIBLE PICE WAS A HAND GUARD AND THE TIP OF A HANDLEBAR. NO BEACON WAS NEEDED TO RESCUE AS I HAD MY RIGHT HAND ON MY AIRBAG READY TO DEPLOY AND WAS ABLE TO USE IT TO FREE MY FACE TO BREATH AND FLAG MY CREW WHEN I HEARD THEM IN ViCINITY. THE SNOWMOBILE TOOK OVER AN HOUR TO DIG OUT, AS WE DUG THROUGH NEARLY CAR SIZED BLOCKS TO GET ITS RESCUE. THERE WERE NO INJURED PARTIES OR EQUIPMENT.

I AM A VERY SEASONED BACKCOUNTRY SNOWMOBILE GUIDE IN UTAH FOR THE PAST SIX SEASONS AND THIS IS MY 36TH SEASON VENTURING INTO THE BACKCOUNTRY. I HAVE AN AVY1/RESCUE/AVY2 CERTIFICATION AND IM ACTIVELY STUDYING FOR MY PRO1 EVALUATION NEXT WEEK. I WOULD SAY THIS AVALANCHE HAD THE POSSIBILITY TO BURY A BUS IN THE GULLY AND IN THE RUN OUT OF IT WOULD EASILY BURY A PERSON TO A DEPTH OF 2-5M. THE RUNOUT ZONE FROM THE TOP OF THE DEBRIS FIELD WAS NO LESS THAN 1KM. I WOULD RATE THIS AS A MODERATE D3R3, HAVING BEEN THE ONE BURIED, THAT IS ME TRYING TO BE OBJECTIVE VERSUS SUBJECTIVE."

This avalanche occurred and was reported by the involved party on January 5th. Their narrative is below in quotes. UAC Forecasters visited the scene the next day, January 6th to investigate the slide. The found a AMu-D2.5-R3-I hard slab avalanche—an very large avalanche that was artifically triggered by a snowmobile, releasing on faceted grains (FC) above the Christmas Eve Rain Crust (CERC). This zone is often heavily wind-loaded, as there is a large fetch just on the windward side of the ridge. On average, the slide was 3-5' deep, but where the cornice was the most heavily wind-loaded it could have been up to 7' deep. There were blocks of hard debris as large as a small car. When the avalanche was initially triggered, it's worth noting that the entire likely slope collapsed, as we saw evidence of a crack extending out from the flank into the lower angle part of the bowl (see photo below). The slide looks to have initiated within the new storm snow, before stepping down to the facets developing just above the CERC. We did not observe any fracturing below the CERC.