Home prices in the nation’s biggest cities fell for the third consecutive month in November, a sign the housing market ended 2011 in a weakened state.

The closely followed Standard & Poor's/Case-Shiller index showed price declines in 19 of the 20 cities it tracks in November – the second month in a row that nearly every city in the index was in negative territory. The index fell 1.3% month-over-month and was down 3.7% from November 2010.

Home prices often fall during the winter months as more purchases are done in the spring and summer months. But the three consecutive downward drops mean prices are likely to continue to keep falling in 2012.

“Despite continued low interest rates and better real GDP growth in the fourth quarter, home prices continue to fall,” David M. Blitzer, chairman of the Index Committee at S&P Indices, said in a statement.

Atlanta continued to show the most pain, posting a new index low. That city was down 2.5% over the month, after dropping 5% in October, 5.9% in September and 2.4% in August. Las Vegas, Seattle and Tampa, Fla., all reached new lows in November.

In Los Angeles, prices were down 1% in November after falling 1.5% the month before. Year over year, L.A. prices are down 5.4.%.

Given the continued malaise in the housing bust, the Obama administration has taken new measures to try and right the housing market as it enters its fifth year of decline. Last week it announced the expansion of its signature foreclosure relief program, a new refinancing plan and a new investigative unit that will further probe the mortgage-related abuses that caused the collapse in housing.