Southeast Mountains

This remotely triggered avalanche near Pittsburg and these fresh avalanches in Red Lady Bowl are good examples of today's primary concern: easily triggering avalanches breaking near the ground on the old, weak snow that sat around in November.  Beware of remote triggering from nearby steep slopes.  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 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. Yesterday’s booming collapses and remote triggers are clear evidence that it is not there yet. We expect to see gradual improvements through the week, but for now, the structure is still reactive enough to warrant patience and conservative terrain choices.