First the good news. For the first time since last July, home prices in U.S. metro areas rose in April, according to the latest S&P/Case-Shiller Home Price Indices. Both the 10- and 20-city composite indices were up, gaining 0.8% and 0.7% respectively.

And then the bad news. These numbers come with a disclaimer: They are not seasonally adjusted. When seasonal factors are taken into account, the 10-city composite’s annual rate of change stayed the same at -3.1% and the 20-city fell to -4.0% from -3.8% in March. And this is after March set a new post-bust low for the 20-city index.

Patrick Newport, U.S. economist at IHS Global Insight, attributes the uptick to the annual ebb and flow of housing tides rather than a real improvement. "This seasonal kick shows up in the April numbers and goes away in October," he said in a statement. "The Case-Shiller indices are likely to post increases during the home buying season and then turn down again."

Pointing to data from the Mortgage Bankers Association that reports nearly 13% of mortgage-holding homeowners are either late on payments or in foreclosure, Newport predicts distressed sales will pull the Chase-Shiller indices down another 5% before they experience improvement. He foresees that turnaround in 2012.

Even with the month’s uptick, six cities logged new index lows in April, including Charlotte, N.C., Chicago, Detroit, Las Vegas, Miami, and Tampa, Fla. Thirteen markets showed improvement from March to April, but 16 cities saw their annual rates of change fall further. Washington, D.C., was the only metro area to post a yearly gain, improving 4%.

"For a real recovery we would need to see several months of increasing home prices, large enough to shift the annual momentum to the positive side," said David Blitzer, chairman of S&P’s Index Committee, in a statement. "In short, better news, but still a lot of questions and a long way to go."

Claire Easley is a senior editor at Builder.

Learn more about markets featured in this article: Charlotte, NC, Chicago, IL, Detroit, MI, Las Vegas, NV, Miami, FL, Tampa, FL, Washington, DC, Greenville, SC.