UPDATE 2-LMC Automotive lowers 2012, 2013 U.S. sales forecasts

* LMC lowers 2013 forecast to 15 mln, from 15.2 mln

* Polk sees 14.3 mln U.S. auto sales in 2012

* Auto sales 40 pct of GDP growth in first quarter

TRAVERSE CITY, Mich., Aug 7 (Reuters) - LMC Automotive lowered its outlook for U.S. auto sales in 2012 and 2013, looking for slower economic growth in the second half of this year than previously anticipated, its chief forecaster said on Tuesday.

LMC, formerly a part of J.D. Power and Associates, cut its 2012 U.S. auto sales forecast to 14.3 million light vehicles from its June outlook of 14.5 million, said Jeff Schuster, vice president of LMC.

LMC also lowered its forecast for next year to 15 million vehicles from 15.2 million.

"We lowered our forecast because of a change from the significant economic growth in the first half to a flatter growth in the second half," Schuster said on the sidelines of the Center for Automotive Research conference in Traverse City, Michigan, where he was also a speaker.

"There is a level of uncertainty among consumers," Schuster said, adding the 2013 auto sales forecast was also lowered because he expects the level of uncertainty to extend into next year.

Schuster said LMC expects the U.S. economy to grow at a rate of 2 percent to 2.25 percent in the second half of 2012, below its previous forecast.

Polk, an industry consultancy, has maintained its 2012 forecast for U.S. light vehicle sales of 14.3 million for several months, said Anthony Pratt of Polk, who also spoke at the conference Tuesday.

Light vehicle sales were 12.8 million last year, indicating a 12 percent sales increase in the 2012 forecast by Polk and LMC.

So far in 2012, auto sales have been a major contributor to growth in U.S. gross domestic product. Generally, auto sales lag growth in the overall economy during a recovery from recession, said Sean McAlinden, chief economist for the Center for Automotive Research.

"After the bottom of a typical recession, there is recovery first in housing and then in auto," McAlinden said. "This time, more than 40 percent of the GDP growth in the first quarter of 2012 was linked to auto and that is unusual."

A positive for the remainder of 2012, said Paul Taylor, economist for the National Automobile Dealers Association, is that inventory on dealer lots has recovered since last year and earlier this year.

A year ago, Toyota Motor Corp and Honda Motor Co sales were constrained by limited inventory after the March earthquake and tsunami in Japan. It took until July for the two leading Japanese automakers in the U.S. market to recover and have more than 50 days of supply on dealer lots, Taylor said.

Ford economist Ellen Hughes-Cromwick said a bright spot for the economy in general in the next few years is the slight uptick in new housing starts. But she said this is a sign of gradual rather than robust economic growth.

LONG-RANGE FORECASTS

LMC expects U.S. auto sales to return to near 17 million annually by 2017. Sales were at that level for a decade through 2007 before the recession bit into sales.

Schuster said once sales return to 17 million a year, those levels will be sustained because there will be less incentive spending to boost sales by automakers than in the last decade.

LMC expects U.S. auto sales to rise to 15.7 million vehicles in 2014, and 16.4 million in 2015.

By 2017, Schuster said, LMC sees sales at 16.9 million vehicles, and that there will be a plateau through 2017, when LMC sees sales at 17.1 million vehicles.

McAlinden and the Center for Automotive Research's long-range forecast is more pessimistic. It sees 2012 U.S. auto sales at 14.2 million, 2013 at 14.6 million, 2014 at 14.9 million and 2015 at 15.5 million.

But McAlinden said U.S. sales will remain near that level through 2022.