It’s the old story on Labor Day weekend: gas prices going up. Experts are saying they’ll stay high for awhile, too, due to a number of factors. A big one is the lingering effect of Hurricane Isaac. As it approached the Gulf coasts of Louisiana and Mississippi, oil drilling rigs in the Gulf and refineries ashore shut down operations for safety purposes and evacuated their personnel. Some damage was also done to shore-based oil handling facilities. Prices are expected to come down some when refineries in many areas switch to their winter fuel formulas later this month.