Pipeline closures in the Midwest and production shortfalls because of Tropical Storm Isaac in the Gulf of Mexico are affecting gasoline prices, analysts said. Tropical Storm Isaac is expected to reach hurricane status Tuesday as it approaches the southern coast of Louisiana. The National Hurricane Center expects Isaac to eventually become a Category 1 storm. U.S. supermajor Chevron said it evacuated personnel from offshore facilities in the Gulf of Mexico as a precaution. \"Some production has been affected due to third-party pipeline closures,\" a statement read. Other operators in the gulf closed facilities ahead of the storm, curbing overall production in the United States. Motor club AAA reports the national average for a gallon of regular unleaded gasoline Tuesday in the United States was $3.75, unchanged from Monday but 4 cents higher than the average for last week. Drivers in Illinois, Michigan and Wisconsin, however, saw their averages top $3.80. Detroit drivers paid on average $3.93 for gasoline Tuesday, 2 cents higher than Monday. A 650-mile pipeline from Chicago was closed following a release of undisclosed amount, said West Shore Pipe Line Co. in a statement. Nancy Cain, a spokeswoman for AAA Michigan, told The Detroit News that gasoline prices should increase because of the gulf storm. Tom Kloza, an analyst at the Oil Price Information System added that while a price increase was expected, it \"should not be a long-term trend.\"