Yeah 40" is a good ballpark reading for woods skiing. Of course there are a lot of factors, most importantly is snow water equivalent (SWE) or just LE in the snowpack. Next up would be type of terrain, low angle vs. steep and additionally how well it is maintained for glade skiing (if at all).
Today was the first day I skied in the woods and the Stake only grew a few inches to 26" or 27" I think, despite the 6-7" storm total through this afternoon (might have grabbed another inch or so this evening).
The upper elevation, low angle woods were more than ready despite the stake value. Old-timer and wise skiers and legendary ski patrollers always use 40" as the rough baseline, but the water in the snowpack really matters. That is what supports the skier/rider above the ground and forms the frozen barrier between you and the ground. More so than inches of snow, but we measure inches of snow much more easily and therefor it's a good rough estimate.
This current snowpack (or icepack) is rock hard and stout. You will not break through it in any way. The last snow/sleet/freezing rain event added significant QPF that almost entirely froze in the snowpack before this system came along. If you don't see a rock, you will not hit a rock... because it's covered in ice. It can be a slick layer but today's snowfall was just dense enough to bond well. It also fluffed up a bit. Good snow growth in a marginal profile and we came out on the right side of it.
Anyway, 40" of upslope or lake effect fluff on 1.5" of water at 25-30:1 ratios is a much different beast than like 4" (maybe more?) of SWE/LE in 27" of "snowpack" (more like block of ice with fresh snow on top). Right now we have the latter.
I liked a 4-8" snowfall, given the surface temperatures. 5-10" higher elevations. The forecast was for a decent QPF event despite temperatures. A widespread 0.50"< SWE event for the region.