3” is enough to mess it up if it stays around & forms facets but 13” would likely be more significant. Last year is a good case study of the worst case scenario. Go to the UAC site & research the chronology from early November on. The year before, 2019~20 was a stable early season & great up until around the middle of February when we had a severe rime event. Again research the chronological building of the snowpack.Good stuff...my next question is what is significant? 3" of "old snow" on the ground? 13"? 3 feet?
There are cures but once the faceted snow is buried it often becomes more problematic.
Weather warm enough to melt the early snow completely is best.
Warmth or rain can change the structure of the snow to something more cohesive & bondable & that can improve things.
A big storm event that creates a natural avalanche cycle can clean a lot of it out & provide a reset to the snowpack but stubborn areas that don’t slide can still be outliers.
Sometimes even the weight of a ton of new snow can kind of crush the underlying weakness & strengthen the weak layers.
Once the snowpack goes completely isothermal but that usually won’t happen till springtime.
There is more to it but those are some of the possible scenarios off the top of my head.
Snow science is just that, a science but a science that is constantly evolving & fooling even the experts.
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