The Northeast and Mid-Atlantic are bracing for a new round of severe storms and possible flash flooding on Tuesday after getting hammered by heavy rain on Saturday.

The greatest threat -- a level 3 out of 5 risk -- will span from northeastern Kentucky to New Jersey, including Pittsburgh, Washington, D.C., Baltimore and Philadelphia.

Numerous severe thunderstorms with potentially destructive winds and tornadoes are possible in this region.

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Rounds of heavy rain and strong storms will move across the Ohio Valley through lunchtime and into the Northeast and Mid-Atlantic through the afternoon and evening.

Areas along the Interstate 95 corridor may possibly get two rounds of storms -- one midday, followed by a bigger round between about 5 p.m. to 8 p.m.

Flash flooding will be a concern for a large swath of the I-95 corridor, from D.C. to Philadelphia to New York City.

Flood watches have been issued from Delaware to southern New York, where rainfall rates could exceed 1 inch per hour, potentially triggering flash flooding, especially in urban areas. Philadelphia and New York City are expected to be included.

More than 1,200 flights have been canceled Tuesday ahead of the storms, with airports in New York City and Washington, D.C., seeing the biggest impacts.

Tuesday's anticipated flooding comes just days after New York City was inundated with pounding rain that flooded streets on Saturday.

ABC News' Melissa Griffin contributed to this report.