Professional Observation

Observation Details

Signs of Unstable Snow

Snow Stability

Bottom Line

On my tour Sunday I came across surface hoar that had formed Saturday night. It was fairly widespread between 4000’ - 6000’ . I did not get any higher in elevation but I assume that the surface hoar might also be present higher up the mountain in areas that are sheltered by the wind.
I also assume that other slopes in our forecast area had surface hoar form on snow surfaces that were sheltered from the wind. This is relevant because the Elkhorn and Wallowa mountains are about to see a significant snow event starting Tuesday night and tapering off Wednesday night/Thursday morning, especially the Southern Wallowas. The new snow load (approximately 2’-4’ forecasted) will be precariously perched on this surface hoar on shady slopes unaffected by wind. Surface hoar is an extremely persistent weak layer that can be especially dangerous when it forms on firm snow surfaces and then is buried by new storm/wind slab. Avalanches that run on surface hoar can do so on slopes that are as gentle as 30 degrees. Watch out for this instability, and instability in general, when you are recreating in this new snow. Take the time to analyze the stability of this dramatic new snow load by digging hand pits and test pits in safe locations. Also be observant of other red flags that might be observable these next few days like the presence of wind transported snow, shooting cracks, and evidence of recent natural avalanches.