By Lauren Casey

PHILADELPHIA (CBS) — A severe thunderstorm watch has been issued for the Delaware and Lehigh Valleys until 9 p.m. as we await the arrival of downpours and thunderstorms this evening and tonight.

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It appears the storm threat could come in two close successive waves — one that will impact more the northern half of the area and the second, more the southern half.

The current severe thunderstorm watch accounts for the first wave of activity. The National Weather Service may issue a second watch this evening.

A few isolated cells may start to fire in the next couple of hours with more organized activity moving into our far western counties after 6 p.m. The main timeframe of concern for Philly and the I-95 corridor looks to be between 8 p.m. and 1 a.m.

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The storm threat will persist until 3 a.m. for the shore and Delaware.

The main threat is damaging winds. Small hail is possible. Heavy downpours and frequent lightning are likely.

Localized flooding is a concern, so if you can stay off the roads tonight, please do so.

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Unfortunately, water rescues are common in our area during these types of events.