GRAINS-Soy at 6-week top on exports, U.S. yield uncertainty

(New throughout; updates prices, adds quotes, changes byline, changes dateline from previous PARIS/SINGAPORE) CHICAGO, Sept 22 (Reuters) - U.S. soybean futures hit a six-week high on Friday on stepped-up export demand and uncertainty about the size of the U.S. crop, analysts said. Corn followed the firm trend, supported by chart-based buying. Chicago Board of Trade December wheat set a one-month high but turned lower. As of 12:41 p.m. CDT (1741 GMT), Chicago Board of Trade November soybeans were up 15-1/4 cents at $9.86 per bushel, the contract's highest since Aug. 10. CBOT December corn was up 4-1/2 cents at $3.54-3/4 a bushel while December wheat was down 1-1/2 cents at $4.51 after climbing to $4.55, its highest since Aug. 16. Soybeans set the firm tone, with the November contract pushing through resistance at its 200-day moving average near $9.78-1/2 to spur technical buying. The market got a boost from the U.S. Department of Agriculture confirming that private exporters sold 190,000 tonnes of U.S. soybeans to Mexico - the 10th daily soybean sales announcement in the last 11 business days. "The demand is just so strong. We are off to a fine start with export shipments. The sales are trailing last year, but certainly coming on here as buyers step forward," said Brian Basting, analyst with Advance Trading. Uncertainty about the national soybean yield also lent support. The USDA in a monthly report last week raised its U.S. yield forecast to 49.9 bushels per acre, up from 49.4 in August. "On paper, we've got a record bean crop. But people are still uncertain about that, and we have to let it play out. Once we get to October, the combines will tell the story," Basting said. CBOT December corn hit a one-week high at $3.56-1/4 but pared gains. The U.S. corn harvest is in its early stages in the core Midwest crop belt, and hot weather this week is helping pushing crops to maturity. CBOT wheat futures turned lower on profit-taking after the front contract hit its highest in a month. But Minneapolis Grain Exchange spring wheat futures were up, with December up 8-1/2 cents at $6.32-3/4 a bushel after hitting a one-week top at $6.33-1/2.

CBOT prices as of 12:40 p.m. CDT (1740 GMT):

Net Pct Volume

Last change change

CBOT wheat WZ7 450.75 -1.75 -0.4 46743 CBOT corn CZ7 354.50 4.25 1.2 107459 CBOT soybeans SX7 985.50 14.75 1.5 128860 CBOT soymeal SMZ7 319.90 7.00 2.2 49628 CBOT soyoil BOZ7 34.28 -0.06 -0.2 52226

NOTE: CBOT December wheat, December corn and November soybeans shown in cents per bushel, December soymeal in dollars per short ton and December soyoil in cents per lb.

(Reporting by Naveen Thukral in Singapore and Gus Trompiz in Paris; Editing by Mark Heinrich and Marguerita Choy)