The following content was provided by meteorologist Gail Martell of MartellCropProjections.com:
The weather forecast is very threatening for corn and soybeans as the heat dome shifts westward this week.
Week Beginning Hot in the Midwest
Temperatures today and tomorrow are predicted near 100 F (37.8 C) today and tomorrow in the Midwest corn and soybean belt, but sharp cooling is predicted Wednesday and Thursday when the jet stream carves out a trough in the Great Lakes – Eastern Midwest.
The cooling would bring temperatures down to 80-82 F , and near normal for mid-summer. Night temperatures in the mid 60s F are also anticipated with a cool and dry Canadian air mass.
The rainfall forecast this week is rather wet, compared to what we've been used to this summer. Bear in mind that the GFS model has persistently over-estimated rainfall, compared to what has actually occurred. This often happens in a drought.
Heat Persisting in Western Corn Belt
A strong ridge of high pressure is expected to shift westward toward the Rocky Mountains this week. This opens the door for cooling in the Great Lakes, as described above, but also brings a hot forecast to corn states west of the Mississippi River.
Des Moines, Iowa, is expecting highs near 100 F Monday and Tuesday, cooling to 95-97 F Wednesday through Friday. Omaha, Nebraska, will be 98 F, or hotter, all week long capped off with a 100 F on Friday.
Western Corn Belt Heat Stress Building
This is a very negative forecast since the worst heat will be concentrated in the best corn areas. East of the Mississippi River corn has already been severely damaged by drought and heat, some fields beyond repair in Illinois, Indiana, Wisconsin and Ohio. Indeed, poor-very poor corn already is 61% in Indiana, the US 5th largest corn state, and 48% in Illinois, the second top corn producing state. By contrast, only 12-18% of corn was considered poor-very poor in Iowa, Nebraska, South Dakota and North Dakota -- all west of the Mississippi River.
Minnesota has the best corn in the United States, but will go downhill this week. July 8 conditions were 77% good-excellent, 18% fair and 5% poor-very poor.
The dome of high pressure is an equal opportunity provider, now shifting westward and damaging corn prospects in the best rated states -- Minnesota, North and South Dakota, Nebraska and Iowa. Note that more corn is produced west of the Mississippi River than to the east by a 60% to 40% ratio.