After four months of gains, house prices across the US ticked down 0.5% in July. It marks the first monthly decline since February, according to the index compiled by default management and residential collateral valuation service provider Integrated Asset Services (IAS). “We are seeing normal seasonality with a slight July pullback, but we are not out of the weeds yet as we will see waves of volatility while the markets correct themselves and settle down,” said president and CEO Dave McCarthy. “Meanwhile, there’s an awful lot going on down at the neighborhood level that will take time to normalize at the top.” Prices in the Las Vegas metropolitan statistical area (MSA) plunged 4.8% in July alone, the largest monthly percentage drop to date. Prices in the Denver and San Francisco MSAs tumbled 3.8% in July. Denver previously remained "stable" since the beginning of 2009, while San Francisco had jumped nearly 8% since February, according to the IAS360 index. “A lot of this volatility has to reflect Washington's near-term influence on price behavior through actions like the foreclosure moratorium,” McCarthy said. “We’re already seeing buying activity moving around in different price segments." The index, which tracks the monthly change in median sales prices of single-family houses across the US, found prices remained up in many MSAs considered "wealthy." The Howard, Md. MSA gained 4.4% in July, for example, while the Prince William, Va. MSA remained 0.5% up from June. Across regional data, the Midwest fared the best in July, gaining 0.2% over June. The South posted a 0.2% decline, followed by a 0.6% slip in the Northeast and a 1.2% decline in the West. Write to Diana Golobay.