Att. art experts Bruegel, question raised by Tales of Winter, The Art of Snow & Ice

In the BBC4 art documentary Tales of Winter: The Art of Snow & Ice the commentary says there is evidence Pieter Bruegel the Elder went back to paintings he had already finished & added snow after the success of Hunters In The Snow. Does anyone know where I can find out more about this evidence & which paintings were altered etc? I have looked at a book which places his art chronologically & Hunters is the first one to exhibit snowfall!

I know this is a very specific question; if no one here can answer, can anyone suggest a good art forum where I might find out, please? Thank you.