Another big rainstorm is headed this way Thursday and it is already posing some major flooding concerns for parts of the area.
There are two problems:
1. We had a lot of rain with Sunday's storm
2. Even more rain should fall Thursday and Thursday night
The Sunday storm caused some localized flooding in our area, but did much more damage farther north. There are still flood warnings in Northern New Jersey from about 4 inches of rain.
The upper portion of the Delaware River had minor flooding. The ground is saturated -- most of the new rain will runoff into creeks and streams and eventually into the Delaware and Schuylkill Rivers.
The National Weather Service doesn't usually issue Flood Watches two full days ahead of a storm but in this case the threat is so obvious that it's a good bet that at least some Flood Warnings will be issued later this week. The Flood Watch issued already covers much of the area as it is through Friday morning.
The NWS hydrologists (who specialize in flooding and ground moisture) tell us that it will only take 1.2 to 2 inches of rain for flooding in virtually all Pennsylvania counties in our area (the lowest amounts are in the Lehigh Valley). Virtually all of our computer models suggest AT LEAST that much will fall, with some estimates up to 6 inches!
Any flooding would start locally, with small streams and creeks late Thursday. It takes longer for the water to make it into the big rivers and move downstream toward the Philly area. So any flooding on the Schuylkill and Delaware would likely happen Friday or even Saturday.
With so much rain in the areas that feed into both rivers from Sunday's storm, the threat of river flooding is significant. Just how bad it will be will of course depend on just how much rain falls, how fast it falls and what areas get hit hardest.
If you live near a vulnerable creek or river, you'll need to pay special attention to news and weather reports over the next few days.
