Northwest Mountains

More than 12" of snow the Northwest Mountains and gusty west winds through last night brought the snowpack to, or potentially past, its tipping point once again.  Triggering a dangerous avalanche remains a serious threat on steep slopes at all elevations today, and a few could release naturally from the alpine.  Slabs could break more than four feet thick below treeline and drifted terrain could produce wide and unsurvivable avalanches, such as the recent wall-to-wall slide in Red Lady Bowl.  Conservative terrain selection is paramount until our buried weak layers catch a break from the ongoing loading over the past 10 days.

Relentless storms since December 27th have kept the snowpack teetering near or past failure.  The storm over-delivered late yesterday and last night, and I won't be surprised to see more destructive naturals from the past 12 hours, particularly from higher elevation, windloaded slopes.  If winds continue to transport snow today, the same threat remains. Today's danger is most pronounced on leeward and cross-loaded terrain near and above treeline where slabs are largest and daily drifting has compounded stress on deeply buried weak layers.  Those types of slopes have produced the most activity in the past few days, such as these recent crushers off of Climax Chutes, Schuylkill Ridge, Peeler Peak, Red Lady Bowl, and Axtell.   Alpine slopes continue to produce every time the wind has snow available for transport, so we are expecting them to remain reactive today after yesterday's storm brought gusts to 50 mph.  You may not see obvious signs of instability underfoot, but finding a thin trigger point in wind-affected terrain is easy enough in steep terrain.  Notice how this slope on Peeler Peak has dozens of thin areas where the slab thins out.  Furthermore, a triggered wind slab can gather enough mass to easily step down to our deeper layers.  

Below treeline is more nuanced.  Slabs are becoming more stubborn to human triggers in the deeper Northwest Mountains. We are starting to see improvements with some buried weak layers, and the slabs are so thick that weak layers are harder to impact.  It might take a stuck snowmobile, an area where the snowpack is thinner, or stepping off your skis deeper into the snowpack to produce the dreaded collapse, which is still a clear possibility based on propagating test results yesterday below treeline on Mt. Axtell and Ohio Pass.  The decreasing sensitivity has been slower near and east of town, where we have gotten regular reports of collapses and remotely triggered slides all week (ex. Cement Creek, Snodgrass).   Below treeline in the Southeast Mountains, slabs are thinner and are perched over more fragile weak layers, making them more reactive to human triggers.