From the National Weather Service:
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE Boston/Norton MA 542 PM EST Wed Dec 18 2019 MAZ019-021-022-182345- Eastern Plymouth-Southern Plymouth-Barnstable- 542 PM EST Wed Dec 18 2019 ...A snow squall will affect Southern Plymouth and Barnstable Counties... At 541 PM EST...A snow squall was near Bourne, or near Plymouth, moving east at 20 mph. Locations impacted include... Plymouth, Barnstable, Brewster, Yarmouth, Wareham, Sandwich, Bourne, Dennis, Mashpee, Harwich and Hyannis. Drivers need to remain alert. These conditions often lead to accidents, especially on highways, since road conditions can change rapidly. Avoid braking suddenly. Consider delaying travel until the squalls pass.