Rainstorm Isaac to Bring Needed Rain to Midwest, Plains

By , Expert Senior Meteorologist
September 01, 2012; 4:53 AM
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Drenching rain from Isaac is forecast by AccuWeather.com to reach some needy drought areas in the Plains and Midwest into the weekend.

Portions of Arkansas, Missouri, Illinois and other Central states will soon be on the receiving end of an "iRainstorm."

While flooding rainfall in southeastern Louisiana and Mississippi will tend to diminish farther inland, some beneficial rain will fall on the parched landscape hundreds, if not a thousand, miles away from the Gulf Coast.

Cities that are likely to receive some rainfall from a diminishing Isaac include Shreveport, La.; Little Rock, Ark.; Tulsa, Okla., Chanute, Kan.; Memphis, Tenn.; and St. Louis, Mo.

The rain is coming far too late for this summer's crops, such as corn. Soybeans will only benefit slightly as we are near the end of the maturity period in most locations. However, according to AccuWeather.com Agricultural Meteorologist Dale Mohler, there is the potential that rain could reach far enough westward to benefit part of the winter wheat areas.

"The wheat over the central and southern Plains is generally planted during September, and replenishing soil moisture prior to planting after summer drought is essential for any new crop," Mohler said.

The rain will also help to green up some pastures. It is possible for some farmers to get a cut of hay in before the winter as a result of Isaac.

Enough rainfall may help to get things moving in the right direction from a hydrological standpoint as well. Some rain is likely to fall on the Missouri, Arkansas, Red (of the South) and the Ohio basins, all of which feed into the lower Mississippi River.

Low water levels from the middle of summer on have negatively affected barge traffic. Barge companies have had to reduce loads, and there have been a couple of instances where vessels ran aground.

River levels and the water table tend to bottom out moving into the autumn as the frequency of thunderstorms diminishes prior to the onset of winter storms.

There is the potential for local rainfall on the order of 6 inches reaching into parts of Arkansas. However, exactly how much rain falls from location to location will depend largely on the forward speed and track of the system.

According to Expert Senior Meteorologist Brett Anderson, "It obviously will not rain everywhere in the Plains and Midwest from the system, so folks should not get their hopes too high just yet."

It appears the rain will not travel much farther west than the easternmost counties of Kansas and Oklahoma and is likely to turn eastward before reaching Nebraska and much of Iowa.

Too Much of a Good Thing

Slow-moving tropical systems often move erratically and can bring tremendous differences in rainfall in only short distances.

Because of the weak steering currents over the central U.S., exactly which places will benefit the most from Isaac's rainfall are unclear.

This means that while some areas will have beneficial rain, other areas may get virtually nothing and a few places could be deluged with too much rain too quickly, leading to flash flooding.

For example, if Isaac's rain were to focus in a narrow swath over the Ozarks, an area prone to dramatic runoff, flash flooding could occur.

According to AccuWeather.com Chief Meteorologist Elliot Abrams, "We believe some rainfall from Isaac's remnants will eventually roll across the Ohio Valley and the Northeast."

As rain from Isaac pushes across the South Central states through the end of the week, the high pressure area to the north will deliver a late-summer heat wave over the North Central states.

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