A favorable corn earworm migration weather pattern is expected over the next 24-48 hours which may lead to increased flights from source regions in the Plains, mid-south, and southern states north into portions of the corn-growing region. Later this evening and into early tomorrow morning, high pressure currently over Kentucky should move little while a cold front in the northwest Plains pushes southeast. An increased pressure gradient between the high pressure and the cold front will cause south to southwest winds to increase in speed especially from Kansas and Oklahoma north into the western corn-growing region and portions of the upper Midwest. Showers and storms are likely to develop along and southeast of the cold front and should become widespread across the eastern Dakotas into Minnesota tonight. The combination of favorable southerly winds and precipitation results in a High corn earworm migration risk for northeast Nebraska, west/northwest Iowa, southwest Minnesota, and southeast South Dakota. This area has the highest probability of seeing new corn earworm migrants. Moderate risks extend north to I-94 in Minnesota and southeast North Dakota as well as east into western Wisconsin, and then southwest along and west of I-35. Low risks are found as far east as eastern Wisconsin, western Illinois, and into Missouri.
The front slides southeast during the day Tuesday. South to southwest winds decrease as the front moves south but closer proximity to active source regions results in a Moderate risk from southeast Missouri into southern Illinois, southern Indiana, and western Ohio for Tuesday night into Wednesday.
Looking ahead to the extended, a compact low pressure system is predicted to move from west to east across the heart of the corn-growing region. Low risks accompany this feature on a daily basis mainly south of I-90 but any flights should be very isolated.