Latest Forecast

Southwesterly flow on the backside of a high pressure system over the western Atlantic will pump warmer and more humid air into the Lower Susquehanna Valley late this week. In addition, a disturbance moving from the central Appalachians through the mid-Atlantic States will trigger scattered showers and thunderstorms this afternoon. The storms will be slow-moving and produce locally heavy downpours, along with frequent lightning and isolated incidents of wind damage. Flash flooding of low-lying, urban- and poor-drainage areas is expected, but streams and creeks should remain well within their banks. After a partly cloudy, warm and muggy Thursday night, a weak cold front will sag southeastward through the Commonwealth later Friday into Friday night and serve as the triggering mechanism for another round of showers and thunderstorms. With high temperatures in the mid 80s to perhaps 90 degrees and dewpoints in the low 70s ahead of the front, the atmosphere will be sufficiently moist and unstable for rapid thunderstorm development and growth. Much like Thursday, locally damaging wind gusts, frequent lightning and torrential downpours will be the main threats from Friday's storms. The storms will likely move more quickly than today, ultimately limiting or even eliminating the flash flood risk. However, downed trees and powerlines are certainly possible in the hardest-hit areas each afternoon, and both PM commutes could be adversely impacted by the storms. The front will push farther south on Saturday but be in close enough proximity to northern MD and southeastern PA for a few showers to still dot the region.