Severe thunderstorms expected after 4 p.m.

Thunderstorms are back in the forecast Tuesday, and the National Weather Service is warning flash flooding may occur during the heaviest downpours. 

Storms are expected to break out by the afternoon, though early Tuesday morning NWS forecasters still were uncertain when the strongest weather. will begin. Their best prediction, issued around 5 a.m., is between 4 p.m. and midnight. 

Rainfall amounts are expected between 1-3 inches, according to NWS.

A NWS flash flood watch, put into effect when conditions such as saturated soil make flooding more likely, will take effect at 4 p.m. and last through 2 a.m. Wednesday for northern portions of Delaware and Maryland, southeast Pennsylvania and New Jersey.

Damaging winds could accompany the strongest storms, NWS warned, and could bring down tree limbs and power lines, possibly leading to outages. 

A strong cold front is expected to move through the region this afternoon and evening, according to NWS. It will lift north with the appearance of a warm front later this week. A warm, humid day is expected before the storms begin in earnest, according to NWS.