With Labor Day drawing closer on the calendar, Iowa motorists can expect to carve a little more off of their paychecks to fill their gas tanks. Ward Lenz is an energy data analyst at the Iowa Department of Natural Resources.Lenz estimates prices will rise to a dollar-40 or one-45 in the next few weeks. Triple-A of Iowa says the current average price for a gallon of gas in the state is a dollar-38. Lenz says that’s a bargain compared to many other states.The national average is around a dollar-50. Lenz says some Iowa service stations were selling gas in the upper one-20s just a week ago, but that didn’t last long.The Triple-A website says the cheapest gas in Iowa right now can be found in Iowa City at one-33, while Sioux City is the most expensive at a dollar-47.