Ag Weather Forum

Fall weather is always a double-edged sword for farmers in the Corn Belt. Likely, conditions that are good for some folks are bad for others. If it is too hot and dry, that is good for the late stages of a maturing crop and harvesting, but bad for those with some time yet and who need some good weather to finish out their summer crop or start planting their winter crop.

That has been the case for the last month or so, where overall warm and dry conditions have caused drought to increase across much of the country. While the complete opposite is not coming true, we will see the potential for some heavy rain to move through during the next week.

The process has already started with a storm system that has developed in Montana. There is some heavy rain there and it has brough an arc of showers and thunderstorms over the Plains since Sept. 17. That is becoming more isolated here for Sept. 18 as the main energy from the system moves north into the Canadian Prairies who are still in the midst of harvest of their spring grains and oilseeds. Slower progress and some damage can be expected there through Sept. 19.

Strong winds are also an issue with the system and areas from Montana into Manitoba may see winds blowing swathed crops around the field or lodging what remains standing. Rainfall from this portion of the system could be heavy in central Montana, where a total of 2 to 3 inches of rain is expected to fall. Other areas in the Northern Plains up through the Canadian Prairies may not see that much, but areas over an inch (25 millimeters) are looking likely across Saskatchewan and Manitoba.

That system has pushed a front into the Plains currently found from the central Dakotas down to eastern New Mexico. With the system tracking northeast during the next 48 hours, the front will be hard to push eastward. Instead, it will largely stall. The northern end of the front will move into the Upper Midwest, but the southern end will be stuck across the midpoint of the Central and Southern Plains.

Scattered showers will develop because of the front, but for the most part, these showers should not be heavy. Models suggest rainfall amounts less than 0.50 inch, though some thunderstorms could increase those totals in the Upper Midwest through Sept. 20.

After that, the situation gets a little more interesting. There is an upper-level trough digging into the West Coast. And instead of moving north into Canada like its predecessor, it will be able to travel straight eastward through the U.S. this weekend and next week. Moving into the Plains, it will form a low-pressure center on the stalled front, wrapping up into a system that should produce more widespread rainfall in the Plains during the weekend, then through the Midwest early next week.

Models are still grappling with how much rain to produce and where exactly the heaviest rains will occur. A look at an ensemble of models can help us to locate the most likely areas that the heavy rain will occur. According to the European model ensembles (the EPS), the most likely areas are in Nebraska and Iowa with an extension into northern Kansas and Missouri. Amounts from last night's model run painted 2-3 inches of rain in that area. In contrast, the American GFS ensembles (GEFS) have less intense rainfall overall. They still have an area of 2-3 inches, but it is smaller in extreme eastern Nebraska and northwest Iowa. But the GEFS spreads out the more moderate rainfall of 1-2 inches farther north through Minnesota and Wisconsin than the EPS. Regardless, it looks like some in the western and central Corn Belt are expected to get some heavy rain because of the storm system which could cause some issues.

Harvest has gotten underway and the heavy rain could lead to significant delays and potential loss of quality. If it comes with severe storms, which may be possible, it could also cause storm damage. At the same time, those across the north, especially in the Dakotas, Minnesota and western Wisconsin have a significant portion of their corn and soybean crops behind developmentally and could use some additional rainfall. Any winter wheat areas in the Plains and Midwest could use some moisture as planting continues to increase. Though those areas are less likely to see heavy rain, all rainfall will be important for establishing root systems.

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John Baranick can be reached at john.baranick@dtn.com

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