I may be wrong but here is what I am guessing is going on with the hard pack slabs on steeps given no new snow. After a dump of snow, a steep run is winch groomed. As Skidude72 wrote, "good grooming, basically cuts the peaks off, and fills in the holes, and doesnt hit dirt ever". Each day skiers ski on such a slope, moving around and compressing the surface snow, while sun, temperature, wind also effect it. Generally due to gravity, snow is pushed down a run. Each additional day the result is less ideal than the first day of grooming after a dump of cold fresh snow. The groomers cannot simply groom the results of a day's skiing else the top areas, knobs, and terrain knees would soon dig down to bare earth.
So one of the first processes must be that they move the pushed down snow back up the hill and fill in all the hollows while making sure the thin areas receive enough snow to keep ski edges above the ground surfaces. Each grooming person probably has good experience knowing where to push snow around to even it out. Each grooming cat has a limit to how deep they can dig down in snow then grind up the results. The highest steepest areas are likely to receive the thinnest pushed back up snow simply due to mechanical leverage. Additionally steep hard pack slabs are due to friction and greater ski/board edge pressures on steeper terrain, least likely to withstand the edging carving the groomed snow off. So snow that had been moved up, in those areas is most rapidly skied off to the smooth firmer base. In most cases the cat does not rototill up any snow at all in the steep slab areas but merely pushes up loose and ground up snow from below and then evenly smooths it out on the surface. So we skiers beyond the first few early bird skiers each day end up skiing the same steep slab surfaces day after day after day.
From day to day there is only a small amount of total snow loss due to wind or sublimation. So a question is where did all the loose snow from the last storm dump that originally was over what became the steep slab area go? I'm guessing that snow becomes a deeper depth in the hollow areas. In other words a slope becomes more even and flat overall after several days with hard pack slab areas thinner and hollow areas deeper. And that is where I think a solution may lie in making better use of the extra snow that ends up in the hollows. Not something that can be done with shallow base depths but once average base depths are more than say 6 feet which is common out West.
So what if instead of starting by moving the pushed down the hill snow back up, grooming cats instead dug into the flat slabs breaking rototilling them up into small ground up material, and then moving up all the pushed down the hill snow to cover such with a deeper layer of loose snow? Well one could expect skiers would take longer before a top layer was skied off but eventually it would be and the result would be yet a new hard slab layer below. There would be a limit to how far down such a layer might be ground up as before long, dirt would be dug up. Thus grooming experts probably figured that out long ago so do not try and break up hard pack slabs but rather have a strategy of waiting for a subsequent storm dump to bury everything so they can start again. Unfortunately The West weather during many seasons has a knack for occasional long droughty periods interspaced with stormy periods.
However here is an idea and would be only a strategy during extended dry periods. Lets say during summer a bunch of small diameter elastic plastic sticks are placed down into the ground in such places of a run at adequate spacings with the above ground crudely calibrated to a reasonable minimal depth height groomers ought not dig below. That would provide those running grooming cats a better visual understanding of snow depths while they were running the cats all through a season. The tops of the sticks might be reflective silver so they might shine in the cat headlamps and something not easily damaged by ski edges or unpleasant for ski edges to pass over. Obviously the strategy would be to always have such a level well below what was likely to be skied up during a day of skiing so during most of a season groomers would never see the plastic sticks. But if they did show it would be a warning to adjust the snow depth in such areas. The current situation seems to be that the steep smooth slab areas are only receiving thin layers on top that are skied off rapidly. If instead all areas received say a good foot of loose snow, I am wondering if the results after a typical Saturday of skiing might end up looking more like a mogul field of small infant bumps many of us enjoy instead of those awful piles of loose snow separated by long lengths of hard slabs. So by using the plastic sticks a groomer might better be able to increase the layer of loose snow moved around each day versus the current system of merely placing a thin layer atop the slabs. Of course this kind of system will only work at results that tend to have multi foot depths of snow and may not be practical in areas where rocks outcrop as knobs in the terrain. However I'd hope there is quite a bit that can be improved even though it sounds like more work for a grooming crew.
Edited by dave_SSS - 1/27/13 at 4:28pm