ARLINGTON, Va. − Two powerful weather systems were careening across the nation Tuesday, threatening to dump up to a foot of snow in some areas while snarling traffic, clogging roadways, shuttering schools and shutting down government offices.

Essex, Hudson and Union counties were originally under a winter storm watch, but the watch was changed to a winter weather advisory Friday afternoon, with forecasters calling for 3 to 5 inches of snow and a light glaze of ice in those areas, as well as eastern Bergen and eastern Passaic.

Winter storm warnings extended from Kentucky to southern New Jersey, and a flood watch was posted for a wide swath of Kentucky, Tennessee, southwest Virginia and northern Georgia. The snow-and-ice mix was expected to become all rain as temperatures climb by Wednesday afternoon.

While a winter storm and ice storm are both wintertime hazards, the impacts can be very different.

Snow is expected to fall throughout the day on Tuesday in Greater Cincinnati. National Weather Service forecasters say that snow is expected to start falling between 6 to 8 a.m. in Cincinnati and Northern Kentucky.

A snowstorm blew into the mid-Atlantic states on Tuesday, causing dozens of accidents on icy roads, prompting school closures and stoking worries about possible power outages.

A snowstorm blew into West Virginia and other mid-Atlantic states on Tuesday, causing dozens of accidents on icy roads, prompting school closures and stoking worries about possible power outages.