(Updates with U.S. trading, adds details)
PARIS/SINGAPORE, Aug 11 (Reuters) - U.S. wheat futures fell on Friday, led lower by a sharp decline in MGEX spring wheat as investors liquidated bullish positions following the U.S. Department of Agriculture's forecast for a bigger-than-expected crop in the northern Plains, traders said.
The selloff pushed the benchmark Chicago Board of Trade soft red winter wheat contract to its lowest in nearly two months. MGEX spring wheat was down 3.3 percent, trading near its lowest since June 27.
Chicago soybean and corn futures edged higher, with some mild bargain buying supporting prices.
All three commodities were on track for weekly declines as the USDA's forecast on Thursday for bumper corn and soybean harvests continued to hang over the market.
Wheat futures were set for a fifth straight weekly loss. For corn and soybean futures, it would be their third straight weekly loss.
At 11:43 a.m. CDT (1643 GMT), Chicago Board of Trade September soft red winter wheat futures were down 4-1/2 cents at $4.36 a bushel.
CBOT November soybeans were 3 cents higher at $9.43-1/4 a bushel and CBOT December corn was up 3 cents at $3.74 a bushel.
The USDA on Thursday projected the U.S. corn yield at 169.5 bushels per acre (bpa), below its previous forecast of 170.7, but well above the average trade estimate of 166.2 bpa.
The USDA also wrongfooted investors by increasing its soybeans yield forecast to 49.4 bpa from 48.0, rather than trimming it as expected.
Traders have been grappling with erratic crop weather that has left some crop belts parched and others soggy. Rainfall was forecast to be limited this week in much of the Midwest, but heavy rain was projected toward the end of next week.
"Market attention now turns back to weather, with yield potential for U.S. soybeans and corn remaining the key focal point for the next month," Rabobank analysts said in a research note.
"We believe that, due to the high level of inconsistency of (corn) crop conditions, it is highly likely that much will remain unknown until harvesting begins."
Wheat markets remained dampened by the USDA's supply outlook, which included a sharp increase in projected global wheat stocks in 2017-18, supported by increased estimates for Russian, Ukrainian and Kazakh crops.
The USDA lifted its Russian crop forecast to a record 77.5 million tonnes, and Russian consultancies SovEcon and IKAR on Friday gave similar estimates for the world's biggest wheat exporter last season. (Additional reporting by Naveen Thukral in Singapore and Gus Trompiz in Paris; editing by David Evans and G Crosse)