Blistering Heat is History in the Midwest

By , Expert Senior Meteorologist
August 12, 2012; 4:22 AM ET
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The drought has taken a hit and the blistering heat is over for much of the Midwest, thanks to a change in the weather pattern.

A southward shift in the jet stream and episodes of soaking rain have taken their toll on the 100-degree heat and drought, which has foiled the corn crop and is poised to negatively affect soybean yields.

The jet stream, which is a ribbon of strong steering winds high in the atmosphere, represents the approximate boundary between cool air to its north and hot air to its south.

The southward shift has allowed weather systems bearing rounds of rain and thunderstorms to drop in from the northern Plains across the Midwest and into part of the southern Plains over the past couple of weeks.

During much of the summer, the jet stream was much farther north and had steered rain away from the central Plains and part of the Ohio Valley.

Once the soil became dry, much of the sun's energy switched to heating the ground, which heated the nearby air.

Portions of Indiana have received between 1 and 3 inches of rain during the middle of this past week. Parts of Missouri have picked up between 0.25 and 1.00 inch of rain in the past few days. In Arkansas, rainfall has ranged from a few drops to a few inches in as many days.

With soil moisture bouncing back and somewhat less intense sunshine compared to six weeks ago, there is less energy available to heat the ground.

More rain is needed on a regular basis to turn the situation around completely. As a result, temperatures will generally average well above normal for the rest of August.

It will take many more rainfall events to replenish reservoirs, raise ground water levels and bring the Mississippi and other rivers back to their normal flows.

According to Long Range Expert Paul Pastelok, "The building El Niño pattern favors above-average rainfall and below-average temperatures over much of the Midwest during the autumn."

However, the same pattern, if it persists, brings the opposite during the winter.

"During an El Niño pattern during the winter, snowfall trends below normal and temperatures average above normal," Pastelok said.

That "below, above" pattern partially to blame for the drought that developed the summer over the region.

The most recent front to cross the Plains and Midwest has shaved temperatures by as much as 20 degrees in some locations.

While brief spikes in heat can still occur in the coming weeks, prolonged 100-degree temperatures from the central Plains to the Ohio Valley are unlikely.

During Tuesday, temperatures in Omaha, Neb., reached a blistering 103 degrees. On Friday, the high in Omaha was a mere 80 degrees, which is below average for the date.

Temperatures continued to reach 100 degrees in St. Louis during the first eight days of August after racking up 18 days with 100-degree temperatures during June and July. The seasonal total now stands at 21 days at 100 degrees. It is possible triple-digit readings may not return to the "Gateway to the West" for the rest of the season.

Heat and drought are both still a concern in the southern Plains and Southwest, but there is some hope of a couple of rain events in the coming weeks.

Farther south, in Oklahoma City, temperatures have climbed to or above 100 degrees on all but one date from July 18 to Aug. 9. On August 5, temperatures peaked at 99 degrees.

Moving forward, high temperatures in Oklahoma City over the next week or so are forecast to generally range from 95 to 100 degrees. While not as extreme as the 100- to 110-degree readings in recent weeks, it is still plenty hot.

Rainfall over the southern Plains into central Texas will be much more spotty, when compared to areas farther north and will raise issues for agriculture, especially pastureland for grazing livestock.

The dry landscape over the southern Plains has been made worse by blistering temperatures in recent weeks and has contributed to a number of wildfires.

The extreme heat hit the Midwest and central Plains hard during June and July and took its toll on corn, which was in the pollinating stage.

The major Midwest cash crop makes up most livestock feed, is irreplaceable and becomes very expensive when yields are expected to be down. And, yields have been lower than expectations for the past several years, resulting in declining reserves.

According to Agricultural Meteorologist Dale Mohler, "Soybeans, which take longer to mature, were not as hard hit, thanks to some rainfall during the critical time in August in general."

This season's wheat crop met or exceeded expectations.

"As far as the upcoming winter wheat crop is concerned on the Plains, some rain is forecast before the end of the month, just prior to planting time in September," Mohler added.

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