At least five North Texas counties, including Collin, Dallas, Denton, Kaufman and Tarrant, were under a winter storm warning as of 9 a.m.

Melting snow: What to expect this weekend: Snow that melts during the day and creates pools of water on roads and sidewalks. When temperatures drop overnight, these puddles of water freeze into black ice. This scenario is especially common after snowstorms where the sun partially melts snow during the day, but the temperature drops again at night.

Black ice is a thin layer that forms on surfaces such as roads, sidewalks and driveways when temperatures are 30 degrees or lower.