A fast moving west to northwest flow weather pattern is expected to persist across much of the central and eastern United States over the next week or so as low pressure remains anchored near the James Bay region of Canada. The result will be quick-moving weather systems that will bring shorter duration southerly wind opportunities along with scattered showers and storms ahead of each successive cold front. Such a pattern is not generally conducive to long distance, widespread corn earworm flights unless there are fields susceptible to damage closer to active source regions in the southern Midwest and mid-south.
Low migration risks are predicted across the eastern Midwest tonight into Thursday morning as a weakening cold front pushes east through the Great Lakes region. Enough southwest winds are expected to be present to allow a few moths to fly north from source regions in Kentucky and Tennessee. An additional Low risk area is back west across the Plains states as the next low pressure/cold front advances into the central part of the country and southerly winds increase ahead of this system.
A Moderate risk is predicted across portions of Kansas, Nebraska, Iowa, and Missouri Thursday night into Friday morning as south to southwest winds increase along with precipitation. A combination of stronger southerly winds and expected precipitation results in an increased risk. Low risks are found as far east as the Mississippi River Thursday night. In the extended period, weather systems will continue to pass quickly through much of the corn-growing region but any southerly wind flow is expected to be weak and mainly confined to the central and southern fields, or from US 20 south. The combination of weak southerly winds and the majority of crops past susceptible stages of insect damage in these areas results in only a Low migration risk for Friday night and Saturday night.