Widespread Storms, Flooding Risk Through Weekend

A broad unsettled pattern will bring waves of showers and thunderstorms across much of the country over the next few days, with the East Coast from northern Florida into southern New England under at least a marginal severe-storm risk Thursday into early Friday. In south‑central Pennsylvania’s Susquehanna Valley a broken line of storms is expected this afternoon/early evening (roughly 1–9 p.m. local), with isolated strong-to-severe cells capable of damaging wind gusts, brief tornadoes, heavy downpours (about 0.25–1.0 inch) and localized flooding in already‑saturated areas. Many local forecast offices have issued Weather Impact/First Alert Days for Thursday through Saturday, noting damaging winds as the main severe threat Thursday while heavier, more widespread rain and elevated flooding risk develop Friday–Saturday. An independent system will drive a sharp cool‑down and strong‑to‑severe thunderstorms in Arizona, where Flood Watches are in effect for parts of southeastern Arizona and portions of Pinal and eastern Maricopa counties, with potential for heavy rain, localized flooding, large hail and damaging winds. Tropical Storm Humberto and a nearby tropical wave are being monitored but are not currently expected to directly affect East Coast forecasts. High pressure building in from Canada should bring cooler, drier “crisp” conditions by mid next week, with highs generally in the 70s for many areas.