* Russia declares state of emergency in key wheat-growing regions
* USDA report expected to show strong corn and soy supply
* Flooding impacts southern Brazil
CHICAGO, May 9 (Reuters) - Chicago wheat futures rose on Thursday as Russia declared a state of emergency in key grain-growing regions due to frosts, while soybeans and corn fell ahead of a monthly U.S. Department of Agriculture (USDA) supply-and-demand report due on Friday.
Three of Russia's key grain-growing areas declared a state of emergency on Wednesday, citing May frosts that government officials say damaged crops and will reduce this year's harvest.
Those regions can expect another frosty night tonight, analysts said.
Chicago Board of Trade (CBOT) July wheat was up 4-1/2 cents at $6.38-1/2 a bushel as of 12:12 p.m. CDT (1712 GMT).
July corn dipped 1 cent to $4.57-1/2 a bushel, while July soybeans were down 16-1/2 cents at $12.11-1/4 a bushel.
The dip in soybeans came as investors expected a strong global supply of the crop to be indicated in Friday's USDA numbers, said Randy Place, analyst with the Hightower Report, keeping prices down.
"We're going to have a burdensome carry-out," he said.
Meanwhile, officials at Brazilian crop agency Emater said torrential rains in the country's Rio Grande do Sul state had slowed the crop's harvest over the last few days.
Roughly a fifth of the soy crop there remains unharvested, along with about 15% of corn, according to preliminary data gathered by the crop agency's regional offices.
Corn is expected to also have a burdensome carry-out, said Place, although to a lesser extent than soybeans, and he noted that Argentina's Rosario grains exchange was cutting its harvest estimate for 2023/24 corn to 47.5 million metric tons from 50 million tons.
Officials with the exchange said the leafhopper plague has ruined around 20% of the corn crop this season.
(Reporting by Renee Hickman in Chicago, Additional reporting by Nigel Hunt in London and Mei Mei Chu in Beijing Editing by Matthew Lewis)
