KANSAS CITY, MISSOURI, US — Tropical Cyclone Debby upset the weather trends for a while in early August by producing abundant to excessive rain across much of the Atlantic Seaboard. There may be more storms affecting the Atlantic Coast before autumn cooling arrives, which could make a mess out of the harvest for crops in the southeastern states. T

here is also a rising potential for wet weather this autumn in the western and central Corn and Soybean Belt and a part of the northern Plains and eastern Canada Prairies. In contrast, areas from the Delta into the northeastern states may be drier than usual. Temperatures should be warm except in the far west.

If the forecast is correct, producers will need to scramble early in the harvest season to beat out the likely change in weather that may make harvesting a bit frustrating later in September and October.

Early indications suggest that the problems with surplus moisture are unlikely to occur right away, although there is potential for greater rainfall in the upper Midwest and a part of the northern Plains during the second half of August and early September. That wetter bias might make it easy for the wetter bias later this autumn to become problematic since some fields already may be a bit wetter biased coming into the harvest.

For the balance of August and early September the odds are high that dryness already evolving in the Delta will prevail and may extend from there through the Appalachian Mountains to interior portions of the northeastern states in the next few weeks. This drier-than-usual bias is not just going to be around for the next few weeks, but it may continue in September, October and possibly November. There will be periods in which rain is likely, but amounts will be lighter than usual. This is one of the few areas in the United States that will have good harvest conditions.

Another favorable harvest region will be in the high Plains region from Nebraska and Colorado to western Texas. These areas are not expected to be too dry, but they will have a good environment to mature and harvest summer crops. The central and southwestern high Plains region may keep a lighter precipitation bias during the autumn, but winter wheat seeding should advance favorably. The region is rarely too wet and that is not very likely this season.

The wetter bias potentially causing harvest delays this autumn will be most notable in late September and October. There will be some hints of the change in late August and early September, but temperatures will be warm enough during that period of time to induce relatively quick drying conditions between rain events. However, once cooling begins it will not take long for the frequent precipitation bias to result in harvest delays.

Three areas are favored for abundant rainfall during the autumn this year. The first will be from Missouri and eastern Kansas into Wisconsin, western Michigan and Minnesota. A second area of wetter biased weather is expected in the Pacific Northwest from northern California to Washington and east into the northern Rocky Mountains. The third area of wet biased conditions will be in Canada’s eastern Prairies and a part of the northern US Plains.

Out of the three areas mentioned above the one that could be a threat to both field progress and unharvested crops will be that in the northern Plains and eastern Canada’s Prairies. The reason for that concern is that spring wheat, barley and late planted canola will all be vulnerable to wet weather if it comes too early. Crop quality declines would occur relatively quickly in these areas and a close watch for the pattern change is warranted.

World Weather, Inc. expects the balance of August to trend a little wetter, but not excessively so. Many crops in the Prairies are maturing quickly this year because of warmer- and drier-biased weather recently. That pattern should prevail through the end of August and possibly into the first week of September. After that, all bets are off and the potential for increasing rain will be on the rise.

Many of the small grain and canola crops produced in the central and western Prairies will be harvested before rainy weather arrives since the summer became too hot and dry in July and continues dry biased today. Eastern wheat, barley and canola producers in the Prairies and the northern Plains may have a little tougher time getting crops out of the fields because of more frequent rain.

As noted previously, the western and central US Corn and Soybean Belt already may have a wetter bias in the soil when autumn arrives and it will not take too many rain systems and cooler temperatures to make some fields too wet. The situation should be closely monitored and plans ought to be made ahead of time as to how the harvest should proceed in anticipation of the wetter bias.

Winter may continue wet biased in the Pacific Northwest and northern Rocky Mountain region as well as northern California. Some of the wetter bias might also shift from the western Midwest to the Atlantic Coast states and southeastern states. A new area of dryness may evolve in the southern Plains and extend into Missouri during winter, but that is quite speculative for now.

Even though the forecast seems so straight forward keep in mind that the peak of the hurricane season is coming in September and that alone could change some of the autumn biases. That is one of the reasons why the wet anomaly is most likely in late September and not earlier than that.

Drew Lerner is senior agricultural meteorologist with World Weather, Inc. He may be reached at worldweather@bizkc.rr.com. World Weather, Inc. forecasts and comments pertaining to present, past and future weather conditions included in this report constitute the corporation’s judgment as of the date of this report and are subject to change without notice.