Current Dry Conditions Could Exert Impacts Through Spring

A dry fall has helped farmers proceed with the harvest without the rainy conditions that have been found in recent autumns.

The drought conditions plaguing the Yankton region could create an impact lasting into next spring, according to the South Dakota state climatologist.

Laura Edwards spoke Thursday on a multi-state webinar including the Great Plains. The U.S. Drought Monitor has classified southeast South Dakota and northeast Nebraska as either severe or extreme drought, with areas to the west considered abnormally dry.

The region has gone weeks without major precipitation, and temperatures have remained 6-12 degrees above normal. Those factors, combined with high winds, have intensified fire hazards. In the latest round, area firefighters responded Thursday afternoon to two fires in Yankton County.

“It’s not just the wildfires (in the western states) but also the field fires during the last month,” Edwards said.

The growing-season temperatures have remained near normal for much of the north central region, including the Dakotas and Nebraska, Edwards said. However, they represent an average of extremes, with 100-degree days giving ways to cold fronts and a major drop in temperatures — freezing in some areas — two days later, she noted.

“We had a flip flopping of warm periods and cool periods, which created near-normal growing season temperatures,” she said.

After coming off major flooding in 2019, this year’s growing season has ranked among the bottom one-third for dryness in South Dakota and in the bottom one-tenth for Nebraska, Edwards said.

“In South Dakota, there are areas that haven’t seen a dry fall like this in a number of years, especially in the eastern part of the state, which is really a change of pace,” she said.

While any major rainfall won’t help this year’s crops, it is necessary for providing topsoil moisture for next spring, according to director Dennis Todey with the U.S. Department of Agriculture (USDA) Midwest Climate Hub.

“We’re beginning to be aware and concerned about refilling the soil moisture profile for whatever is the depth in your area — if it’s 4, 5 or 6 feet of soil — that contains certain moisture,” said Todey, a former South Dakota state climatologist.

A number of areas haven’t experienced their first hard freeze, but that looks to change based on the next week’s forecast, Edwards said.

The prolonged drought could determine how crops will react to the lower temperatures, Todey said.

“Typically, we assume 28 degrees at any time of an hour or more will end the season. It can be 28-32 degrees and, as long as the crops are in good condition, they can stand several hours before they are done,” he said. “But there are some mitigating factors that include crop stress in some other way, limited soil moisture, disease or derecho damage to crops.”

Under the current soil conditions, freezing weather isn’t necessary to exert a negative impact, he added.

“When some of these very dry conditions get radiated, you have cooling where the temperatures don’t drop that low, but the crops emit radiation into the sky,” he said. “That cools the leaves enough so there is some damage and you can lose the crops completely.”

Todey experienced such a season during 2004 while he was in South Dakota.

“They didn’t record temperatures below 32 degrees, but there was widespread crop damage because of fairly radiated conditions,” he said. “The crops lost all their heat and were stressed, which did them in.”

So far, the fall harvest is going strong nationally for corn and soybeans, according to USDA meteorologist Brad Rippey.

The Midwest and Great Plains agricultural update for Oct. 15 showed record U.S. yields for corn at 178.4 bushels an acre and a record-tying yield for soybeans at 51.9 bushels an acre. There was very little heat stress, and many days were below 95 degrees.

However, more than half the country is reporting topsoil moisture of short to very short, Rippey said. In addition, sustained damage was seen in areas such as the Aug. 10 derecho in Iowa and the Sept. 8-9 frost in North Dakota.

Other areas had a wet spring, late freeze in May and pockets of summer drought.

The potential corn yield for 2020 would be a record 165 bushels an acre. At this time, 41% has been harvested, which is 9% ahead of average. For soybeans, the condition is rated 63% good to excellent.

In terms of weather, the long-range outlook shows a strong trend for a La Nina weather pattern coming off the Pacific Ocean and settling in the north-central U.S. The odds stand at 85-90% chance of it staying through winter and 60% chance of carrying into the spring.

A La Nina presence shows a high degree of variability in the north-central states, dating back to 1950, Edwards said. “A lot of years, it brings cooler-than-average temperatures, and it’s not always the same across the region,” she said.

The same unpredictability goes for precipitation, Edwards said. “It’s kind of a mixed bag in the Dakotas. We don’t have a strong sense of wetter or drier in any of those years dating back to 1950,” she said.

A strong La Nina may bring more rain or snow, depending on the area, Todey said. The soil moisture and condition will play a major role in how it receives any further precipitation, he added.

With saturated or heavy topsoil, any further moisture will run over it, Todey said. Drier soil can take in more of the rain or snow.

Looking ahead, the seven-day outlook calls for relatively quiet weather. The 8- to 14-day outlook leans toward cooler weather. November looks to remain drier for South Dakota and Nebraska.

The outlook for November-January shows the north-central states with equal chances of warmer, colder or average temperatures. As for precipitation, the northern plains could be caught between a wetter pattern in the northwestern U.S. and drier weather to the south.

“For December through February, we’ll see more impact of La Nina with cooler temperatures, which also favors wetter weather in the northern tier of states,” Edwards said.

“We’ve had a trend of many wetter winters in the last few decades and that is also a player. La Nina is not the only thing.”

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