Corn earworm migration probabilities are on the increase especially in the extended period and beyond as the weather pattern transitions from a predominantly northwest flow to one of more zonal or even southwest flow for a time next week. This pattern change may result in more widespread and heavier corn earworm flights so continue to monitor subsequent forecasts this week and next for potential increases in both risk level and coverage area.
At the start of the period, high pressure currently located right over the heart of the corn-growing region is expected to shift off to the east today into tonight as low pressure develops in the Rockies or over the central High Plains region. Southerly winds will likely return to the Plains states and a Low migration risk is in place tonight into Friday morning for areas mainly south of the Nebraska/South Dakota border east into Iowa and all west of US 65. The risk area shifts east Friday night into Saturday morning as the weather system moves east. Fields between I-35 and I-75 and also south of US 20, or from Missouri and Iowa east into Ohio and mainly south of the Great Lakes region are under a Low risk during this time. The whole system moves out with a brief break in migration risks for late in the weekend.
By next week, southerly wind flow in advance of a potentially stronger low pressure system pushes Low migration risks back into the forecast as early as Sunday night and Moderate risks are already predicted across portions of Nebraska, Iowa, South Dakota, and Minnesota for Monday night and Tuesday with Low risks into the Dakotas, Minnesota, Wisconsin, and east to the Mississippi River.