* Forecasts of cool, wet weather add pressure on corn, soybeans * U.S. plan to provide relief to refiners on biofuel mandates weighs * Strong rise in the U.S. dollar weighs on prices (Updates with extended losses, wheat turning lower, dollar rise) By Naveen Thukral and Sybille de La Hamaide SINGAPORE/PARIS, June 17 (Reuters) - Chicago corn futures slid more than 2% on Thursday and soybeans dropped to a six-week low, as forecasts of improved weather in parts of the United States and a strong rise in the U.S. dollar weighed on prices. Wheat followed the downward trend after rising earlier in Asian trade and in the previous session. "Weather forecasters continue to look for rain and cooler temperatures this weekend, while dry and hot weather prevails in the north west of the U.S. Midwest until then," said Tobin Gorey, director of agricultural strategy at Commonwealth Bank of Australia. "That weather pattern is the market"s fixation for now." The most-active corn contract on the Chicago Board of Trade (CBOT) was down 2.4% to $6.56-3/4 a bushel by 1045 GMT, having closed up 0.8% in the previous session. Most traded soybeans November were down 1.5% to $13.25-1/2 a bushel, the weakest since April 30. Wheat futures fell 1.2% to $6.54-3/4 a bushel. Forecasts for improving weather in the U.S. Midwest crop belt weighed on corn and soybean futures, despite a drop in condition ratings for both crops. Soybeans have been under pressure recently following news the U.S. Environmental Protection Agency is considering ways to provide relief to U.S. oil refiners from mandates requiring the blending of biofuels including soy-based biodiesel. A stronger dollar, which makes the greenback-priced commodities expensive for buyers holding other currencies, also weighed on prices. The dollar rose to its highest level in more than two months versus major peers after the Federal Reserve brought forward its projections for the first post-pandemic interest rate hikes into 2023. Wheat exports from Russia, Ukraine and Kazakhstan will rise in 2021/22, a Reuters poll showed, driven by high crops and stockpiles as well as increased global demand. The group, which exports its wheat mainly via the Black Sea to customers in Africa and the Middle East, faces tougher competition as prospects for this year"s crop are also good in the European Union. Prices at 1045 GMT Last Change Pct End Ytd Move 2020 Pct Move CBOT wheat 654.75 -8.00 -1.21 640.50 2.22 CBOT corn 656.75 -16.25 -2.41 484.00 35.69 CBOT soy 1323.50 -19.75 -1.47 1311.00 0.95 Paris wheat 205.25 -1.25 -0.61 213.25 -3.75 Paris maize 255.75 -2.50 -0.97 219.00 16.78 Paris rapeseed 490.75 -7.50 -1.51 418.25 17.33 WTI crude oil 72.02 -0.13 -0.18 48.52 48.43 Euro/dlr 1.19 -0.01 -0.55 1.2213 -2.33 Most active contracts - Wheat, corn and soy US cents/bushel, Paris futures in euros per tonne (Reporting by Naveen Thukral Editing by Subhranshu Sahu and Frances Kerry)