Ag Weather Forum

Storm Chances North

John Baranick
By  John Baranick , DTN Meteorologist
The pattern will allow for thunderstorms to develop in the Plains and move into the western Midwest through the end of the week, followed by a front this weekend. (DTN graphic)

Crop ratings dipped by a couple of points last week. Most states held their own or dropped a couple of points. The most notable state was Iowa, where good-to-excellent ratings for corn dropped for a third consecutive week down to 69% total; the Iowa soybean good-to-excellent ratings declined to 70%. This is despite some decent weather conditions last week. Much of the country saw at least some precipitation and many areas in the drier sections of the Dakotas, Iowa, and eastern Midwest saw amounts over 1/2 inch. But it should be no surprise that 1/2 inch of rain just isn't enough this time of year, especially for western Iowa where deficits have become quite large. Much of the state has had rainfall only 30% to 50% of normal over the last 30 days.

But a major player not included in these ratings is the derecho that occurred over the Midwest on Aug. 10. A cluster of thunderstorms grew into a complex of strong to severe thunderstorms along the Missouri River Valley south of Sioux Falls to almost Omaha and raced eastward through Iowa, southern Wisconsin, northern Illinois, northern Indiana, and southern Michigan. Wind gusts over 100 miles per hour (mph) were recorded in Iowa with many 80- to 90-mph gusts occurring in eastern Iowa and northern Illinois. The winds caused some extensive damage, especially to corn and grain storage facilities. Areas bypassed by the wind damage received rain estimated at 1/2 to 1 inch and locally heavier, up to 3 inches. The rain will likely have a positive effect on crop health in these areas as we continue to fill corn and soybeans.

And we're not done yet. The pattern is changing to a strong ridge in the west and a weak one in the east. The weakness in the east should allow for thunderstorms to build in the Plains and move into at least the western Midwest through the remainder of the week. Rainfall amounts of around one inch are expected along the Missouri River Valley from North Dakota to St. Louis, including the majority of Iowa. Additionally, a front will move through the country east of the Rockies over the weekend into early next week providing additional rainfall. Overall, this is a good setup for filling corn and soybeans through the Corn Belt.

But it is not such a good setup for the Delta. Only some isolated showers and mostly dry conditions have been observed over the last couple of weeks. Dryness has started to spread from the middle of the region all the way through the south. Soil moisture is still being modeled as adequate for most of the region, but if organized shower activity does not happen, declines in soybean and cotton conditions can be expected as both are filling.

Although precipitation for much of West Texas and the southwestern Plains has been near to above normal over the last month, most of the region remains in long-term drought. Heat was not as prevalent last week, but it looks like it will be this week. Temperatures in the triple digits appear likely through Aug. 16 before a cold front can provide some relief. This will continue to stress filling cotton and put pressure on irrigation, not to mention stress to livestock as well.

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

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