A severe thunderstorm watch is in effect for far north counties, including Grayson, Denton, Wise, Jack, Cooke and Collin, until 4 p.m. Large hail and damaging winds are the primary threat.Thursday is a First Alert Weather Day for the potential of strong to severe storms in the afternoon and evening hours.

As a new air mass moves into the region, storms are possible in the afternoon and evening. The storms are expected to intensify as the day progresses.

A large area of severe thunderstorms is forecast into Tuesday night and will overlap areas in the Ohio, Tennessee and middle Mississippi valleys that were hit by deadly and damaging storms, forecasters say.