NE : The mid - Atlantic will most likely have severe weather forecast . A derecho forms thanks in large part to warm , humid air , instability in the atmosphere and jet-stream winds , which can organize the storms into isolated storms called super cells . NEW : Trees and power lines are downed west of Chicago . 50 mph wind gusts , dime - sized hail in Chicago ; stronger winds seen elsewhere . Tornado watches seen as far east as Pennsylvania , West Virginia .
NE : The mid - Atlantic will most likely have severe weather forecast . NEW : Trees and power lines are downed west of Chicago . 50 mph wind gusts , dime - sized hail in Chicago ; stronger winds seen elsewhere . Tornado watches seen as far east as Pennsylvania , West Virginia .