Southeast Mountains

Developing persistent slabs are smaller and less common in the snow-starved Southeast Mountains. However, stay alert for exceptions because there was a notable amount of avalanche activity over the weekend in the adjacent Northwest Mountains.  Small amounts of snow and wind drifting have formed thin slabs in a few areas at higher elevations in the past week.    Monitor for isolated instabilities in very steep or high consequence terrain: stiff slabs in leeward terrain features or shallow sluffs in wind protected terrain.  Snow coverage is thin in most steep terrain; any avalanche, regardless of size, will rough you up over rocks and stumps.  

When a few inches of new snow and increased winds trigger a handful of natural hard slabs up to D2 in size, you know that's a sign of a crappy weak layer.   Horrible weak layers are pervasive across our mountains on west, north, and east aspects following the dry spell and shallow snowpack left behind by the big Thanksgiving cycle.  By itself, weak snow is not all that dangerous but requires caution in very steep terrain where the cohesionless, sugary snow gains volume as a point-release avalanche.  The bigger hazard is anywhere that slabs have formed over this rotten snowpack.  With relatively modest amounts of snow (up to 18" in the NW Mountains and a few inches in the SE Mtns) and big wind events in the past week, slabs have formed on specific, wind-loaded features in the snow-favored areas and more isolated features in the snow-starved areas.  Because these slabs are formed almost exclusively from wind loading, if you recognize the features that collect wind loading from NW to SW winds, you can identify the most problematic slopes at higher elevations. If you'd prefer a simpler approach (with better snow quality), seek out the soft snow in wind-protected terrain and manage for small point releases if your slope angles tilt steeper than about 37 degrees.  

Looking at the avalanche patterns since our first in a series of wind events started a week ago, you'll see where slabs have been most active:  east and northeast-facing slopes above 11,000' in the Northwest Mountains.  This makes sense because those aspects held rotten weak layers on their bed surfaces, and have now received the brunt of wind loading.  The NW Mountains have been significantly favored by snowfall, so more snow was available to drift into slabs.    Where are the surprises lurking?   There are isolated slopes in the Southeast Mountains with large fetches that have collected enough drifted snow to form problematic slabs.  Evan was targeting these concerns a few days ago in West Brush Creek without finding a significant problem, but there's a lot of alpine terrain east of town that is difficult for us to access early season, so we have less data. The other surprises are lurking on north and west aspects.  These slopes also share the same horrendous weak layers, but they've been less active because winds have done more eroding than loading.  If you find a drifted slab on those aspects, treat it as guilty.  You'll find those more isolated drifts in midslope concavities or gullies that act as catcher's mitts for drifting snow, such as these gullies on Irwin's West Wall.