A forecast for a developing drought in the U.S. southern Plains is the latest threat to dwindling world wheat supplies. Hard red winter wheat, a bright spot this year compared to paltry spring wheat production, was recently planted and will need a robust harvest next year to counteract a global shortfall in supplies. But a three-month U.S. weather forecast calling for drought in key growing areas could put the crop at risk in places like Kansas, the biggest producer of the grain used to make all-purpose flour. “The seeded wheat will need moisture to get established before going dormant this winter,” Justin Gilpin, chief executive officer of the Kansas Wheat Commission, said in an interview.