Stubborn wind slabs in Flathead Range

Recent northeasterly winds formed stubborn wind slabs at higher elevations on Nyack Mtn, a change from earlier in the week.  

• Above 5500', evidence of wind drifting (from Monday night?) included trees without snow on their branches, stiff drifts 4" to 1' thick, and erosional/depositional textures.
• We were unable to trigger any slides on wind loaded test slopes, but we did produce cracks up to 8' long, evidence that slabs are getting harder to trigger. 
• With stiff windslabs giving variable feedback, we opted to avoid any consequential terrain with evidence of crossloading.  We skied steep terrain, but kept to wind eroded slopes in the alpine and found stable, wind protected powder elsewhere.  
• The persistent slab structure is losing its cohesion due to cold temps and faceting at mid/low elevations.  We got a mix of propagating and non-propagating results in stability tests down 3 feet at the 2/2 crust.