Partially good news.
In short. It seems to be possible to get at least Spindly Taproots amidst the winter, in an area already covered in snow. Just get a shovel (not necessary make) and clear the area of snow. Of course, the terrain under snow should be appropriate. Nice devs' work, if intended.
It's partially good because cleaning a half-decent area takes probably too much energy for a hungry newbie. But at least it's something.
The second downside is that most forageables seem to be really season-dependent and not appearing during winter at all, regardless of terrain.
What I did this winter.
I was noticing that forageables in the areas partially covered with snow are found on the "real" terrain only.
Later I thought that it may be possible to get them spawning if I clean the ground back.
It was a long and tedious work for my mouse and me, but 2 or 3 hours and some thousands of energy later I cleared something like 70x40 meters.
Logging out for 20 minutes gave nothing twice despite it was a forest area (namely Sombre Bramble and Pine Barren) rich with everything before, and I went to sleep.
When I visited it today, there was 2 Spindly Taproots. Though as almost a day passed, the area got already covered with snow for, like, 50%?
I hope it wasn't a visual glitch, because I forgot to actually pick them...
Now I'm cleaning it again to see if anything else will spawn.