Monday July 18 – A Severe Thunderstorm Watch has been issued for our entire area until 8 PM this evening. A line of thunderstorms has developed this afternoon and thanks to the high heat and humidity are already over performing. The risk here is for winds over 60 mph, large hail over 1 inch in diameter, and an isolated tornado. As I wrote this morning and many time in the past, the surface wind direction is critical to track with reference to central Maryland. Storms erupting in the mountains and tracking across southern PA are the first wave. Should the winds continue to back from the south to southeast off of the Chesapeake Bay, then there will be an enhancement to this line east of the mountains which can flare up in metro areas like we had this past Saturday. Here is the updated radar simulation.