I used to be a junior technician in the tech guys section at the local pc world (I know, I know, boo - hiss) and we used to see this all the time. Whip the back off the laptop, quick blast with an air compressor and all is well again. You can get cans of compressed air for a couple of quid now, always good to keep one handy to get rid of dust.
Snow still just as it was before, light and nothing substantial.
Anyway, I'm fed up with watching almost nothing falling so I'm off to bed. Night all!