Corn pollination is rolling along in many areas and, right on cue, here comes a round of hotter and drier weather during the next week to ten days. Seven-day precipitation forecasts from Friday, July 6, suggest no more than light amounts across the central U.S. This drier trend will, in turn, be accompanied by a warming trend over the next week in the Midwest. Even with the high crop ratings in effect for corn and soybeans right now, some increased crop stress by mid-July cannot be ruled out.
A primary driver of the pattern over the next ten days will be the evolution of upper-atmosphere high pressure, usually called a ridge. My colleague Joel Burgio describes the ridge's evolution as follows:
"The subtropical ridge will range from the central Plains through the southwest and central Midwest during the first 2 to 3 days of the outlook period. The ridge settles southward into the southern Midwest and Delta at the end of the period, in response to a low-pressure trough moving from the Northern Plains across the northern Midwest during this time. The U.S. model is somewhat slower and a little deeper with the trough and surface cold front as it reaches the Midwest late in the period.
"As a result of this stronger surface front, the U.S. model features somewhat more rainfall at the end of the period in the western Midwest and in Kansas. There are two schools of thought on this. First, the prospect of a cold front with showers and thunderstorms is something we have seen many times this spring and early summer, so it is hard to ignore outright. Second, upper-level ridges have a habit of being strongest in the middle summer period, and this may limit the potential for this front to act as earlier fronts have behaved."
The drier trend, along with growing degree day totals, will certainly be welcome in the flooded areas of the northwestern Midwest. Waterlogged crops will benefit; also, spraying has been hard to do with the frequent rains. But, the lack of moisture will just keep extracting moisture from the soils of the southwestern Midwest -- northern Missouri, southern Iowa, western Illinois and eastern Kansas. Soil moisture deficits in this sector are around four inches -- or more -- below average.
Also, the upcoming pattern will keep the nighttime temperatures at above-normal levels. As recently noted, the warm overnight conditions can put corn into a situation where the plant cannot put as much of its energy into the kernel, because of its need to use more energy to maintain plant viability -- just to stay alive. So, weather fortunes are once again taking on a leading role here in midsummer.
Bryce Anderson can be reached at email@example.com
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