When in a snow biome the snow doesn't update correctly. You must right click it with you're hand or another item to get it to properly update.
Before this area was clear of snow. I logged out and back in and all the snow was there again.
Before is when I logged back in.
After is when I simply right clicked with my axe which updated the block states correcting them and making them disappear.
The same happens if you click snow it will instantly snap to taller snow because it didn't update.