Could Hurricane Isaac help alleviate the drought over at least part of the U.S.?
Yes! A quick look at the drought index maps show the most severely hit areas are over the central Plains, central Mississippi valley and the lower Great Lakes region. Projections of the heaviest rainfall show that's the same area that will see the most substantial rainfall-4 to 10" in places. While there is the potential for localized flooding (especially urban areas where storm drains may back up) the rain should help alleviate the drought considerably! Of course, some crops are past help. But the rain will also raise the level of the Mississippi river; low river levels have caused numerous navigation problems.