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CHICAGO, March 1 (Reuters) - U.S. wheat futures rose for the sixth day in a row on Thursday, with new forecasts calling for extended dryness in the U.S. Plains pushing prices to fresh 7-1/2-month highs, traders said.
Soybean futures rallied to a 13-month high on signs of strong export data. Parched soils in Argentina that threatened to reduce crop yields in that key South American supplier continued to underpin prices.
Corn futures also rose on the back of gains in soybeans and wheat, with signs of strong export demand lending further support.
All three commodities closed near their session highs.
Wheat, which has risen 15.4 percent during its current winning streak, notched the biggest gains as conditions in the Plains have worsened.
"The forecast for the next three weeks shows more of the same, with moisture receipts expected to remain well below normal for these areas," Don Keeney, senior agricultural meteorologist for Radiant Solutions, said in a note to clients. "Wheat will be emerging from dormancy over the next few weeks, and the very dry soils will allow crop conditions to deteriorate further."
Chicago Board of Trade May soft red winter wheat gained 20-1/2 cents to close at $5.15-1/2 a bushel. The most-active contract topped out at $5.18 a bushel, its highest since July 14.
K.C. hard red winter wheat futures, which track the crop being grown in the Plains, shot up 4.7 percent and hit their highest since July 12.
"The crops will soon ... attempt to start growing again, but fail, in dry soils," said Tobin Gorey, director of agricultural strategy, Commonwealth Bank of Australia.
CBOT May soybean futures closed 12-1/2 cents higher at $10.68 a bushel. The most-active soybean contract hit its highest since Jan. 23, 2017.
The U.S. Agriculture Department on Thursday morning reported weekly soybean export sales of 979,900 tonnes, which topped forecasts for 400,000 tonnes to 800,000 tonnes.
USDA also announced snap soybean sales on Thursday that totalled 246,000 tonnes, including 120,000 tonnes for delivery to China during the current marketing year.
CBOT May corn futures ended 4-1/4 cents higher at $3.86-1/4 a bushel.
USDA's weekly report showed corn export sales of 1.753 million tonnes, up from 1.621 million a week ago. Analysts forecasts ranged from 1 million tonnes to 1.5 million tonnes. (Additional reporting by Colin Packham in Sydney; editing by Jonathan Oatis and Tom Brown)