Drought may expand its grip on north-central US this summer

Drought conditions over the northern Plains may expand across more of the north-central United States as the summer progresses.

Most summer rainfall over the U.S. Great Plains is produced by large complexes of thunderstorms during the summer.

An anticipated weather pattern this summer may have these storms taking a path around, rather than through the region.

"We expect a large area of high pressure to become a semi-permanent feature over the Central states this summer," according to AccuWeather Lead Long-Range Meteorologist Paul Pastelok.

A high pressure area is a large, mainly dry weather system that spins clockwise. When these systems become very strong, they can extend through multiple levels of the atmosphere and shut down rainfall.

"If the high pressure area develops as we believe, the large complexes of thunderstorms will be lacking, rainfall will be limited and heat will build to well above-average levels," Pastelok said.

Occasional rounds of showers and thunderstorms are expected to skip across the United States/Canada border and dip into the Great Lakes region.

"Storms may be frequent enough to turn things around along the northern tier of the U.S. such as North Dakota, northern Minnesota and northeastern Montana and to hold off widespread drought around the Great Lakes and Ohio Valley," Pastelok said.

"Once in a while, the tail of these systems may bring a thunderstorm and rain to small localized areas," AccuWeather Long-Range Meteorologist Mike Doll added.

Considering the high evaporation rates in the summer, not enough rain may fall to avoid a broad expanding area of drought in parts of the central Plains and Midwest.

As of the middle of June, portions of the Dakotas were already experiencing severe drought, while abnormally dry conditions were present in parts of Minnesota, Illinois, Iowa, Missouri, Indiana and Michigan, according to the U.S Drought Monitor.

"The area where we are most concerned about drought conditions developing and expanding as the summer progresses is eastern Nebraska, Iowa, northern Missouri, South Dakota, southern Minnesota and perhaps parts of eastern Kansas," Pastelok said.

The drought could become significant enough to impact agriculture in the region, including the corn crop.

There has been some rain in part of the area over the past 10 days, and some additional rain will fall into the fourth week of June.

But while this may help in the short term, the key will be the amount of rain that falls during the middle part of the summer.

"The heat and dryness developing through late June are likely to become dominant in July and may continue well into August," Pastelok said.

For most of the region, the critical time for corn is during July, according to AccuWeather's team of agricultural meteorologists. This is because July is the prime month when the corn is pollinating and kernels are filling out.

A lack of sufficient soil moisture during July can significantly cut yields later on.

However, even one complex of drenching thunderstorms can have a positive effect on corn and other crops during July.

In addition to areas of below-average rainfall already, warmth has been no stranger to the region.

During the first half of June, temperatures over much of the central and northern Plains have averaged 4 to 8 degrees Fahrenheit above normal.

Should this trend continue through the middle of the summer, as AccuWeather's long range team believes it will, evaporation rates will be accelerated and sporadic rainfall will be critical for agriculture.

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