GRAINS-Soy slides as crop ratings, weather boost supply prospects

* Soybeans fall after USDA raises crop ratings

* Corn follows soybeans down despite dip in ratings

* Wheat turns lower as U.S. spring wheat harvest begins

(New throughout, updates prices, market activity and comments; new byline, changes dateline from previous PARIS/SYDNEY) CHICAGO, Aug 1 (Reuters) - U.S. soybean futures fell more than 3 percent on Tuesday after an unexpected improvement in the condition of U.S. crops eased concerns that recent hot weather would hurt yields. Corn and wheat futures followed soybeans lower. As of 12:11 p.m. CDT (1711 GMT), Chicago Board of Trade November soybean futures were down 32 cents at $9.75-1/4 per bushel after dipping to $9.71-3/4, the contract's lowest since July 3. Technical selling accelerated as the contract fell below its 200-day moving average near $9.86-1/2. Benchmark CBOT December corn was off 6-3/4 cents at $3.78 a bushel after hitting a one-month low at $3.75-3/4. CBOT September wheat was down 9 cents at $4.65-1/2 a bushel. Soybeans led the way down after the U.S. Department of Agriculture late Monday rated 59 percent of the U.S. soy crop in good to excellent condition, up from 57 percent a week earlier. Analysts surveyed by Reuters on average had expected no change.

"Soybean yield potential may not be as low as some had expected," MaxYield Cooperative market analyst Karl Setzer wrote in a note to clients. "For today, (the) trade feels the crop is getting better, not worse," Setzer wrote. Pressure also stemmed from forecasts for mild Midwest temperatures in August, the key month for determining soybean yields. "The general feeling is now that ... we have a two-week outlook that calls for favorable growing conditions and no real threat of heat, we could have a bean crop that really shapes up," said Terry Reilly, senior analyst with Futures International in Chicago. The USDA rated 61 percent of the U.S. corn crop as good to excellent, slightly below analysts' forecasts. Wheat futures turned lower after early advances, possibly reflecting some harvest pressure in the northern Plains. The USDA said the harvest of the drought-hit U.S. spring wheat crop was 9 percent complete, matching the five-year average. In South Dakota, the harvest was 46 percent complete, ahead of the five-year average of 31 percent. Ahead of the USDA's Aug. 10 supply/demand reports, traders await crop estimates from private firms including INTL FCStone, which expected to release its figures later on Tuesday.

CBOT prices as of 12:14 p.m. CDT (1714 GMT):

Net Pct Volume Last change change CBOT wheat WU7 464.50 -10.00 -2.1 61253 CBOT corn CZ7 378.00 -6.75 -1.8 145453 CBOT soybeans SX7 976.75 -30.5 -3.0 150767 CBOT soymeal SMZ7 316.40 -9.00 -2.8 55130 CBOT soyoil BOZ7 34.38 -0.75 -2.1 57382

NOTE: CBOT September 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.

(Additional reporting by Gus Trompiz in Paris and Colin Packham in Sydney; Editing by Jane Merriman and David Gregorio)