Thunderstorms and Flash Flood Watch warnings: which areas are at risk? Parts of the Northeast are under threat from severe weather until the early hours of Sunday morning. Rains could result in flash floods through Senday. EMILY ELCONIN REUTERS Severe Thunderstorm Watch for parts of the Northeast in effect until 11 pm Saturday, but severe weather could persist into the early hours of Sunday. The ground is already soaked from the wettest July since 1975 providing the conditions for flash floods through Sunday. Tornado warnings were briefly issued in counties along the New York and New Jersey border. The severe thunderstorms could bring lightning and strong, potentially damaging winds to communities northwest of the I-95 corridor