The following content was provided by meteorologist Gail Martell of MartellCropProjections.com:
Iowa Corn Yield Estimated Too High
USDA has predicted a surprisingly high corn yield in Iowa in the September report, despite one of the worst late summer droughts on record. The projected yield at 162 bushels per acre September 1 would be 9% below trend. The state corn production may finish worse than USDA's estimate because of intense late-summer drought. The July-August rainfall was only 43% of normal with 3.56 inches, the lowest value in 40 years.
Conditions were slightly drier than 2012, though drought last season was accompanied by extreme heat so it is not a good comparison. This season, summer growing conditions were mostly cooler than normal. In addition the 2012 drought began in the spring, leaving fields extremely dry by August. This year a "flash drought" developed suddenly in July, becoming very intense in August.
A better weather analog for late summer drought is 1976 when the Iowa corn yield finished 11.5% below trend. As the USDA is currently at 9% below-trend, there is room for further deterioration.
Iowa corn this spring was planted very late making the August drought damage worse. Iowa is the leading US corn state with an 18-19% share of US production.
Midwest Forecast Wet
Generous rainfall is anticipated in the Midwest this week at least .75 inch of rainfall, but over one inch in many areas. Modest rainfall developed on the weekend along a Canadian cool front sinking southward through the Midwest. More rain is still coming.
The dome of high pressure that blocked Midwest showers previously has been pushed westward into the Rocky Mountains and is no longer an obstacle to rainfall in the heartland. Cool dry high pressure will prevail today causing abundant sunshine. The balance of the week looks unsettled with a chance for showers nearly every day.
The five-day forecast from the Hydrometeorological Prediction Center shows a bolus of heavy rainfall sweeping northward out of southern Texas, then bending northeast. Corn and soybean states Iowa, Missouri, Illinois, Wisconsin, Indiana and Michigan are expecting very generous rainfall from .75 to 1.5 inches, locally more. Hurricane Ingrid now in southern Texas would send a bolus of extremely heavy rain inland which would be swept up by the jet stream and directed northward up towards Iowa.
Unsettled weather is expect to prevail 4 days this week in some portion of the Midwest, beginning tomorrow September 17. North Dakota, South Dakota, Minnesota and northwest Wisconsin would be exempted; however most of the north-central Midwest received generous weekend rains.
Would heavy rain be too late to help Midwest crops? Rainfall would be beneficial for late pod-filling in soybeans. However, in some areas soybeans are already too far gone from severe drought. Moreover temperatures are rapidly chilling down, retarding plant activity. The seasonal cooling is due to less-intense solar energy and shorter daylight hours.
Maximum temperatures Tuesday September 16 are expected to be upper 60s-low 70s F for highs and mid 40s-low 50s F at night. Mean temperatures in mid August are warmer, low-mid 80s F during the day and 60s F at night. To optimize rainfall in soybeans, warmer temperatures are required to drive plant development.