Clear Capital issued a market alert Friday after identifying what the company called a “dramatic change” in U.S. home prices.

The valuation firm’s index is showing a 5.9 percent two-month drop in home prices through September and October, representing a magnitude and speed of decline not seen since March 2009, the height of the housing downturn.

“Clear Capital’s latest data through October 22 shows even more pronounced price declines than our most recent Home Data Index market report released two weeks ago,” said Dr. Alex Villacorta, senior statistician for Clear Capital. “At the national level, home prices are clearly experiencing a dramatic drop from the tax credit-induced

highs, effectively wiping out all of the gains obtained during the flurry of activity just preceding the tax credit expiration.”

With a falloff of nearly 6 percent in just two months, home prices are now at the same level as in mid-April 2010, two weeks prior to the expiration of the federal government’s homebuyer tax credit, according to Clear Capital.

The company says this significant drop in prices, in advance of the typical winter housing market slowdowns, “paints an ominous picture” that will likely show up in other home data indices in the coming months.

Clear Capital gathers market data on home prices in near real-time and as a result, reports its analysis ahead of other industry gauges (typically two months in front of other indices).

The company says both its home price index and the S&P/Case-Shiller indices have displayed consistent market peak, trough, secondary trough, and tax credit run-ups.

Clear Capital says if previous correlations between the Clear Capital and S&P/Case-Shiller reports continue as expected, the next two months will show a similar downward trend in S&P/Case Shiller numbers.

According to Clear Capital, this latest downturn in home price trends is expected to continue through the first quarter of 2011.