Mid-sized housing markets saw home price decreases in 13 of 20 markets studied by Altos Research with an indication that further cooling is on the way. Prices flattened and are trending downward, the analytics firm said. The median price was $255,093 in mid-September, down less than 1% from $256,021 in mid-August. The biggest three-month price increases were in Durham, N.C. (5.69%); Boulder, Colo. (4.40%); and Reno, N.V. (2.93%). Durham had the largest one-month increase in median price, with a 1.68% increase to $280,313. Eleven markets saw prices decline at the three-month level. The three biggest decreases were Naples, Fla. (-3.15%); Pittsburgh, Pa. (- 2.76%); and Charleston, S.C. (-1.20%). The leaders in the three-month price increases are Durham (5.69%), Boulder (4.40%), and Reno (2.93%). Durham had the largest one-month increase in median price, with a 1.68% increase to $280,313. Inventory in mid-sized cities studied by Altos was down in 18 of the 20 markets, Altos said in its mid-cities 20-city composite report that suggests a loss of momentum from earlier summer activity. Inventory was down 1.79% decrease over last month. Over a three-month period, inventory has decreased 2.08%. See below chart for a sampling of median price changes in several of the markets studied. (Click on chart to expand.) Write to Kerry Curry. Follow her on Twitter @communicatorKLC.