Yes, BLUBBERS is a Scrabble word!

Letter values in Scrabble US: B 3, L 1, U 1, B 3, B 3, E 1, R 1, S 1.

Is it a valid word?

BLUBBERS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

an insulating layer of fat under the skin of whales and other large marine mammals; used as a source of oil
excess bodily weight

Also: blubber out.