Gunnison

Our troublesome snowpack requires patience and discipline.  Numerous large natural avalanches ran from alpine slopes the past two days from increased winds, and human-triggered slides have been relentless.  Slabs are often an ideal depth for human triggering, and remain sensitive where they formed over the shallow and weak snowpacks left behind in steep terrain by the Thanksgiving cycle.  Last week featured numerous close calls in the Elk Mountains (see our weekly summary).   Conservative terrain choices on west, north, east, and high elevation south aspects are essential.  The safest riding is on slope angles under 30 degrees or wind protected southerly slopes at lower elevations.  

Just as our team was starting to question if the alpine was becoming stubborn, given a relatively quiet avalanche week and a lack of collapses observed above treeline, the winds increased, and numerous large naturals came crashing down. When large persistent slabs release during a small wind slab event, that’s a telltale sign of an unhappy/untrustworthy snowpack. With Thursday’s and Friday’s winds coming from an atypical northeast direction in some areas, they stirred to life some high south and southwest facing terrain that has been quiet since Christmas, and we expanded the persistent slab rose accordingly. This video from Teo yesterday describes the situation, and you can see the changing pattern in persistent slab avalanche activity if you filter the last three days. Some of our limited data suggest the sporadic and thin facet layer above the Christmas crust may be more of an issue in the shallower Southeast Mountains, but for now, we’ll apply a broad brush to both zones and re-evaluate as we get more info. 

But enough about the alpine, we'll all be seeking better visibility below treeline today.  Below treeline has proven to be consistently talkative and reactive in snowpacks around or just under a meter deep. Relentless collapses and remote triggers from areas like West Brush Creek yesterday and Cement Creek, Mt. Emmons, Copper Creek, and Schuylkill Ridge earlier this week highlight a dangerous snowpack that has remained easy to trigger longer than we usually see.  As our video from Schuylkill Ridge demonstrates, even deeper parts of our forecast area have plenty of slopes with this shallower and more reactive snow depth due to the Thanksgiving cycle. As another example, this video of a rider-triggered slide near Kebler Pass shows a snowpack that looks to be around 80 cm or less, while nearby Irwin weather stations have a 125 cm snowpack in flat terrain, which has become quieter underfoot now. 

Changing patterns of wind loading vs. erosion, previous avalanche activity or a lack thereof, and other components of spatial variability mean that not all slopes highlighted by the persistent slab rose are problematic. However, making those assessments often carries uncertainty with serious consequences on all but the smallest terrain-trap-free features.  More reliable and stress-free solutions are patience, low-angle terrain, or southerly aspects protected from the recent winds.