* Bumper U.S. corn, soy harvest seen advancing
* Lagging exports hang over soybean, wheat markets
* Traders start looking ahead to USDA crop data (Updates with U.S. trading, changes dateline from PARIS/SYDNEY)
By Tom Polansek
CHICAGO, Oct 31 (Reuters) - U.S. soybean futures turned higher on Wednesday after falling to a six-week low as traders awaited further clues about the size of the U.S. harvest and the impact of the U.S.-China trade war on exports.
Corn and wheat futures stumbled.
Traders were assessing U.S. weather forecasts, which have improved after rains hampered soy and corn harvesting in the Midwest in recent weeks. Traders were also starting to look ahead to monthly supply-and-demand forecasts due out from the U.S. Department of Agriculture next week, with some predicting the agency may trim its corn yield estimate.
"Right now people are just kind of taking a wait-and-see attitude," said Jim Gerlach, president of Indiana-based broker A/C Trading.
Gerlach added that traders were squaring up positions on the last day of the month.
Chicago Board of Trade November soybeans were up 3-1/4 cents at $8.36-3/4 by 11:55 a.m. CDT (1655 GMT). Earlier in the session, the front-month contract hit its lowest price since Sept. 20.
December corn futures were down 1-1/2 cents at $3.63-1/4 a bushel. CBOT December wheat slipped 5-3/4 cents to $4.94 a bushel.
Uncertainty about demand continued to hang over the markets, as the trade row between Washington and Beijing has nearly halted U.S. soybean export sales to China, the world's top importer of the oilseed.
Soren Schroder, chief executive officer of global grain merchant Bunge Ltd , said he expected a small cut in China's year-on-year soy imports due to the trade dispute. China also may not need to revert to buying U.S. soybeans before the next South American crop is available, he said.
Schroder's comments came after U.S. President Donald Trump warned he was ready to impose billions of dollars' worth of new tariffs if a deal with China was not possible.
"It seems most inside the trade are now mentally preparing for the next round of tariffs and the trade conflict to deepen further before improving," Kevin Van Trump, president of U.S. consultancy Farm Direction, said in a note.
U.S. wheat exports have also struggled amid competition for global business from Russia, the world's biggest supplier.
The U.S. dollar edged up to a fresh 16-month high against a basket of key currencies, putting the greenback on pace for a seventh straight month of gains. A strong dollar makes U.S. farm products less attractive to importers. (Reporting by Tom Polansek in Chicago Additional reporting by Gus Trompiz in Paris and Colin Packham in Sydney Editing by Jane Merriman and Matthew Lewis)