GRAINS-Wheat gains for fifth session on weather concerns, soybeans firm

* Wheat near 5 year top as dryness raises concerns over output

* Ample world supplies to limit gains in wheat prices

* Soybeans up for 4th session as Brazilians plant in dry soil (Adds quote on paragraphs 4-5, details on Ukraine crop, Russian exports)

SINGAPORE, Oct 8 (Reuters) - Chicago soybean futures rose for a fifth consecutive session on Thursday, buoyed by concerns over dry weather in key exporting countries.

Soybeans gained more ground as a lack of rainfall in the world’s top producer Brazil raised supply concerns.

However, abundant global wheat supplies are expected to cap gains in Chicago futures.

“Weather issues are lifting prices,” said Ole Houe, director of advisory services at agriculture brokerage IKON Commodities in Sydney.

“...Chicago futures as well as Russia wheat are trading at 5-year high levels and that does not seem to compute well with the global supply and demand fundamentals even with the weather risk taken into account.”

The most-active wheat contract on the Chicago Board of Trade (CBOT) added 0.3% to $6.09-1/2 a bushel, as of 0337 GMT, after closing up 2.5% on Wednesday when prices hit their highest since July 2015.

Soybeans were up 0.3% at $10.54 a bushel and corn rose 0.2% to $3.89-1/2 a bushel.

Dryness has raised concerns among traders about the prospects for wheat planting in the U.S. Plains and the Black Sea region and for soybean planting in Brazil.

U.S. agricultural exports to China hit $2.15 billion in August, the highest ever for the month, led by strong soybean exports.

Kyiv-based consultancy ProAgro on Wednesday cut its Ukraine 2020 grain harvest forecast to 69.44 million tonnes from the previous forecast of 71.34 million tonnes due to a smaller corn output.

Russia has upgraded its forecast for the 2020/21 grain export surplus by 5 million tonnes to 50 million, as it prepares to announce an export quota for January-June.

Russia, one of the world’s biggest wheat exporters, is harvesting a large crop this year. But rising domestic prices and a weak rouble have brought the grain export quota mechanism, used in spring at the height of the COVID-19 pandemic, back onto the government agenda recently.

Commodity funds were net buyers of CBOT wheat, corn, soybean and soymeal futures contracts on Wednesday, and net sellers of soyoil futures, traders said. (Reporting by Naveen Thukral; Editing by Rashmi Aich)