Forecasters say pop-up showers could lead to flash flooding on Monday. The threat of pop-up storms will return by midweek and last through the weekend. A damp and dreary start to the workweek will lead to sunshine and more comfortable temperatures on Monday, but forecasters say we're not done with the wet weather. What we know:Leftover showers from a round of overnight storms will continue to make their way across the Philadelphia area on Monday morning. What's next:The chance of pop-up storms will return on Wednesday and last throughout the remainder of the week, with temps in the upper 80s.