The course has a benign look as Tiger Woods (white shirt, leading the pack) practices Wednesday. (Charlie Riedel / AP)

The weather forecast for the first day of the U.S. Open on Thursday is dire — with the worst of the storm expected to hit the Merion Golf Club outside Philadelphia during the afternoon rounds that include Tiger Woods.

Mere rain and thunderstorms would be preferable to what some forecasters are predicting: hail, damaging winds and, perhaps, a derecho with nearly 60-mile-per-hour winds.

A cart path was flooded Monday. (Gene J. Puskar / AP)

The grounds are already saturated from over six inches of rain that fell over the last week. Two low-lying holes, Nos. 11 and 12, are especially vulnerable to flooding and the National Weather Service has issued a flood warning for the area that includes Merion.

“Our meteorologist is saying that he doesn’t have a definite [projection for the amount of rainfall],” Mike Davis, the U.S. Golf Association’s executive director, said Wednesday. “He’s looking at models right now, but it could be from quarter-to-half an inch up to two-to-three inches. It really depends on — this isn’t a huge, in terms of a wide front coming our way — so it depends on really what hits us or how lucky or unlucky we are.”

Woods, playing in a group with Rory McIlroy and Adam Scott, tees off at 1:14 p.m. EDT.

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