Southeast Mountains

Mr. Avalanche is getting a little time to rest and becoming slightly less irritable, but if you go poking that slumbering beast today, there is still a high probability of triggering another dangerous avalanche. Recent remotely triggered avalanches near Pittsburg and avalanches in Red Lady Bowl are good examples of today's primary concern: avalanches breaking near the ground on the old, weak base.  The danger is most acute on the north half of the compass and could also exist on some high-elevation southerly slopes that held onto early-season snow.  Observers yesterday reported good stability in steep terrain where snowfall from the past week fell on dirt. 

As natural activity from Saturday’s storm rolls into the database, clear patterns are emerging about where you can trigger avalanches on old, weak layers near the ground. The north half of the compass—especially sheltered or leeward terrain—has been the most active. These slopes held weak, sugary facets through the November drought and are most problematic. With last week’s winds often loading toward the southeast, we’ve also seen avalanches on high, southerly terrain.  Some of these upper-elevation, leeward slopes retained old snow through the drought and deserve equal caution. While much of the recent activity likely failed as wind slabs on short-lived weak layers, our late-November fieldwork shows that a collapsible crust-facet combo forms the base of the snowpack on some high southeast or west-facing slopes.  This leaves the door open for persistent slab behavior as well.

Below treeline, the November weak layer is buried about a foot deep in the shallow areas near town and roughly two feet deep in snow favored zones like Kebler Pass and the Upper Slate—deeper still at higher elevations. Slab thickness is currently in the “sweet spot” for human triggering, and we’re essentially in a holding pattern until the snowpack starts to show signs of adjusting.

Over the coming days, we'll begin to observe fewer obvious signs of instability as weak layers slowly adjust to the current load. Avalanche activity will become less frequent, but if someone pokes the bear too many times, we can expect to see more dangerous avalanches occur. Then, as we progress into the forecasted dry weather later this week, we'll eventually start to see slabs faceting away with clear, cold nights, creating strong temperature gradients in the shallow snowpack. The circle of life for a persistent slab in the Crested Butte backcountry will then be ready to start all over again whenever we see the next winter storm. 

One other note, there is still a little time to ride southerly-facing slopes before they get cooked. A good strategy right now could be to ride south and avoid the most dangerous avalanche areas, while giving them more time to become less reactive. The snowpack on southerly-facing slopes is shallow, but if you do your homework, you can find planar slopes with enough snow for a great ride.