GRAINS-Wheat breaks five-session rally on improving U.S. outlook

* Melting snow benefits dry U.S. wheat areas

* U.S. exporters sell old-crop U.S. corn to unknown

* Soybeans rise on demand

(Recasts with U.S. trading; changes dateline, pvs PARIS/SYDNEY) CHICAGO, March 4 (Reuters) - U.S. wheat futures fell for the first time in five sessions on Monday as melting snow eased concerns about persistent dryness in key growing areas of the Great Plains. Warming temperatures in the drought-stricken U.S. Plains are melting piles of snow that accumulated during two blizzards in late February, said Don Keeney, meteorologist for MDA EarthSat Weather. Dry weather linked to the worst U.S. drought in more than half a century has stressed hard red winter wheat in the region since the crop was planted last spring, raising concerns about the size of the spring harvest. However, the snow "is putting a lot of welcome moisture into the ground," Keeney said.

Chicago Board of Trade May wheat, the most actively traded contract, fell 2.3 percent to $7.03-3/4 a bushel by 10:30 a.m CST (1630 GMT). Improving moisture conditions also weighed on deferred corn futures, said Don Roose, president of U.S. Commodities. May corn slipped 0.5 percent to $7.05 a bushel. However, December corn, which represents the crop that will be harvested next autumn, fell 1 percent to $5.51 a bushel. "What you have to ask yourself daily is, 'Is the drought getting bigger or smaller?"' Roose said. "The last two weeks, the drought's been getting smaller. That's a headwind."

CORN DEMAND Export demand helped underpin nearby corn prices as supplies are tight following the drought. Private exporters struck deals to sell 100,000 tonnes of U.S. corn to unknown destinations for delivery in the marketing year that ends Aug. 31, according to the U.S. Department of Agriculture. Concerns about tight global soy supplies also helped boost soybeans as logistical problems have delayed shipments of the oilseed from Brazil, which is expected to be the top soy exporter this year, traders said. The delays have shifted some business to the United States, they said. May soybeans gained 0.4 percent to $14.48-1/2 a bushel. Still, South America is expected to produce a massive crop. Brazilian forecaster Agroconsult raised its forecast for record soy and corn crops, analyst Marcos Rubin said, citing favorable climate in the southern producing regions. Brazil will likely harvest 84.2 million tonnes of soybeans, he said, up from the firm's 84 million tonnes forecast in January. The corn crop forecast was raised to 75 million tonnes, compared with 74.7 million tonnes previously, he said.

Prices at 10:22 a.m. CST (1622 GMT)

LAST NET PCT YTD CHG CHG CHG CBOT corn 723.00 -1.25 -0.2% 11.8% CBOT soy 1474.50 10.00 0.7% 23.0% CBOT meal 426.80 -0.50 -0.1% 37.9% CBOT soyoil 49.73 0.26 0.5% -4.5% CBOT wheat 699.25 -14.00 -2.0% 7.1% #VALUE! #VALUE!US crude 89.70 -0.98 -1.1% -9.2% Dow Jones 14,067 -23 -0.2% 15.1% Gold 1573.50 -1.36 -0.1% 0.6% Euro/dollar 1.3008 -0.0012 -0.1% 0.5% Dollar Index 82.2790 -0.0340 0.0% 2.6% #VALUE!

*Front month contracts. CBOT contracts in cents per bushel except rice which is in dollars per hundredweight. Paris wheat in euros a tonne and London wheat in pounds per tonne

(Additional reporting by Sam Nelson in Chicago; Editing by Marguerita Choy)