Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Unlikely
- Size
- 2
Earlier this week, my partner and I triggered this avalanche from a distance near Murdock Peak. More on the slide HERE.
Upper elevation slopes facing the north half of the compass harbor early-season snow that grew weak and sugary during the November dryspell. Last weeks storms buried the weak layer 1-2 feet deep, creating our main avalanche hazard, persistent slab avalanches. Suspect terrain includes shady, upper-elevation, rocky slopes where, once triggered, today's avalanches could break wider than you expect and prove to be a nasty ride.
As time wears on, we are seeing fewer red flags, or obvious clues of instability like recent avalanches, cracking, and collapsing. Sometimes we need to take a deeper look under the hood to understand what is going on. A quick shovel excavation reveals a strong, dense slab over weak, sugary snow. That combo creates a trap-door feeling when we're trenching our sled or ski track.
A snowpit at 10,000' on a north slope with a height of snow around 65cm or two feet. The blue crystal card shows the interface between the dense slab 1-2 feet thick, that sits above weak and sugary facets near the ground.