I don't think they're even possible?
White light (sunlight) must shine through water/transparency to create the spectrum. Snow isn't transparent, it couldn't have the same effect.
Just drove up to runcorn castle. It's 70m higher than my house. We had snow falling and lying, but this was from a 10 minute shower here
Second picture is the mersey, just a height comparison.
Milder air tied in with these showers. Just isn't right. 0.9C as this one arrived, 1.4C now.. Falling as rain and hail. Dewpoint is -2C...
Radar shows heavy echoes above, it's only just noticeable in the lamppost. Absolute joke.