CHICAGO, May 17 (Reuters) - U.S. soybean and corn futures closed mixed on Monday, with nearby contracts firming on support from tight supplies and strength in the cash market, while forecasts for warm weather that will boost crop development in the U.S. Midwest pressured new-crop issues, traders said.

"The outlook warmed up for the Midwest over the weekend ... which should finally stimulate increased emergence and growth of this year’s corn and soybean crops over the next 10 days," Arlan Suderman, chief commodities economist at StoneX, said in a note to clients.

Wheat futures dropped on the outlook for some much-needed rain in the U.S. Plains, with MGEX spring wheat sagging 3.5% to its lowest since April 22.

Chicago Board of Trade July corn futures settled up 8-3/4 cents at $6.52-1/2 a bushel. The new-crop December corn contract dropped 5-1/2 cents to $5.37-1/4 a bushel.

Strong export demand underpinned the corn market.

Private exporters reported the sale of 1.7 million tonnes of corn to China for delivery in the 2021/22 marketing year, the U.S. Agriculture Department said. It was the fourth corn sale of more than 1 million tonnes to China this month.

The USDA also said exporters sold 128,000 tonnes of corn to Mexico.

CBOT July soybeans were up 1-1/4 cents at $15.87-1/2 a bushel, while new-crop November shed 3-3/4 cents to $13.97.

U.S. soy processors crushed fewer soybeans than expected in April, with the month's crush volume sinking to the second lowest in 19 months, data released by the National Oilseed Processors Association showed. Soy processor downtime and tight stocks of the oilseed limited the crushing pace.

CBOT July soft red winter wheat was down 7-1/2 cents at $6.99-3/4 a bushel. MGEX spring wheat for July delivery fell 25-3/4 cents to $7.15 a bushel. (Reporting by Mark Weinraub; Additional reporting by Michael Hogan in Hamburg and Naveen Thukral in Singapore; Eiting by Barbara Lewis and Peter Cooney)