The Cardinals won for the third time in four games to jump a half game past Pittsburgh into second place in the National League Central. The Astros lost their sixth in a row.
Lohse (13-2) surrendered only three hits in seven innings while winning his seventh straight decision.
Jay then singled home Furcal with the tying run and took second on the throw home. Jay moved to third on a ground out and scored on a wild pitch by Norris on a 2-0 count to Matt Holliday.
Yadier Molina singled in the final St. Louis run in the eighth.
Jason Motte worked a perfect ninth for his 29th save.
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