Public Observation #2023-1152

April 21, 2023 10:46 PM
Observation Date:
April 20, 2023
Zone or Region:
Central Cascades
Tombstone Pass
Did you trigger any avalanches? 
Was it intentional? 
Avalanche Type:
Cornice Break
D1: Relatively harmless to people
Smallish, non-overhanging NE cornice collapsed under my touring partner, who managed to get his feet down, grab the edge and was hauled back up on top with my help. Break was about 8’ wide leaving a 5’ crown (again this was a vertical cornice, NOT a 5’ deep slab). Slide ran down maybe 300-400 vertical feet without major entrainment. Tough to fully gauge the depth from above but probably a D1.5–seemed unlikely to bury a person fully but maybe partially.

There were much larger cornices nearby that we gave a wide berth to. My partner admittedly lost track somewhat of his proximity to the edge as we were discussing descent paths down the opposite side of the ridge.

We also deliberately triggered minor wind slab avalanches with ski in cross loaded slopes near the bottom of our descent in the northwest drainages below Cone Peak.
Did you see shooting cracks? 
Did you experience collapsing or whumpfing? 
Toured from Tombstone Pass Snowpark to summit of Cone Peak, descended west aspect of Cone, ascended north side of Iron Mountain and descended steep eastern aspect of Iron.

Widely variable snow. Entire south (upper) face of Cone Peak is wind scoured to white ice and snice. Northwestern descent of Cone presented heavy powder with wind effect ranging from none to moderate. Steep east glades descending from summit of Iron Mountain had surprisingly deep powder that was heavy but unconsolidated with little to no sign of wind-/storm slab.

Overall, this is a complex zone and we encountered a really diverse set of conditions. We triggered three avalanches—an accidentally cornice break on the summit of Cone Peak which had the potential to take my touring partner for a ride but fortunately did not (more below), and two minor wind slabs triggered through deliberate ski cuts in a low consequence zone about 800 vertical feet down NW drainages from Cone. We found heavy but stable snow on Iron (some predictable dry/loose stuff notwithstanding), though we stayed far away from cornices and complex ridge lines.

The weather had been shifting and we found more loading on W aspects (which is reflective of the ESE winds on our tour day), significant cornices in N-NE-E aspects, and smaller newer cornices on W aspects.

Also worth noting that snowpack is stunningly deep for the low elevation and time of year. Snow stake near HWY20 at 4200’ showed 9.5’ on the ground.