Rapidly worsening conditions have created concerns about flash drought in a number of areas, according to a National Weather Service (NWS) official.
Flash drought refers to relatively short periods of warm surface temperature and abnormally low and rapidly decreasing soil temperature, NWS hydrologist Mike Gillispie told the Press & Dakotan.
About 80 percent of South Dakota suffers drought, with northeast Nebraska also showing dry conditions. In southeast South Dakota, Charles Mix and Douglas counties have fallen into drought status.
“We’re still not really in a flash drought in southeastern South Dakota, thanks to fairly widespread rainfall amounts of 1 to 3 inches — with higher amounts to 5 inches — in the past several days,” Gillispie said Thursday.
“This (recent rainfall) has put a temporary stop to any drought or flash drought expansion for most of the area. But if we go another week with above-normal temperatures and little to no rainfall, the expansion will ramp up very quickly again due to the soil moisture supply already being depleted from late May to early June.”
The NWS analyzes flash droughts based on observations of precipitation, temperature, soil moisture and evapotranspiration, Gillispie said.
“There are even different types of flash droughts,” he said. “One is caused by very warm temperatures and low soil moisture. Another is caused by precipitation deficits. Most flash droughts are actually a combination of these.”
The current situation around parts of South Dakota, Nebraska and Iowa is a combination, he said. The precipitation during the past 30-90 days didn’t show huge deficits, but amounts from the past 10-20 days fell much below normal.
Areas that missed this week’s heavy rains have fallen to less than 25 percent of normal rainfall, Gillispie said.
Recent rainfall throughout South Dakota has put drought expansion on hold and offers hope for the summer-season crops and gardens.
“After some record warmth in early June and several weeks of dry weather, rainfall finally came to the region this week,” said Laura Edwards, SDSU Extension state climatologist.
According to data, most of eastern South Dakota received about 2 inches of rain.
“The rains brought welcome relief to dry soils that were affecting crop growth, as well as gardens and yards,” Edwards said in a news release.
Despite some severe weather and thunderstorm winds, she added that early damage reports show relatively few losses.
“Most corn and soybeans were small enough to avoid significant hail or wind injury,” she said.
However, the region isn’t out of danger, Edwards said.
“Climatologists and others will be watching the drought closely over the next couple of weeks, however, as the forecast appears to turn dry and warm again,” she said.
“Drought conditions are severe. Recent rains will not be able to sustain crops and gardens for very long.”
The extreme heat of recent weeks has created tremendous stress for crops, Gillispie said. Large rainfall events are needed just to offset the current conditions, he said.
“Temperatures have been running above normal for a significant length of time, and (they) have been extremely above normal in the last couple weeks,” he said.
Large rainfall events are needed just to offset the current conditions, he said.
“Evapotranspiration rates have been very high, averaging 4.5 to 6.5 inches in the last 2-3 weeks,” he said. “That means, for the soil moisture just to break even, we would have to have received 4-6 inches or more of rainfall in the last 2-3 weeks.”
Much of the region has fallen far short of those numbers, even with this week’s burst of focused precipitation, Gillispie said.
“Without additional rain, crops and plant growth will start showing negative impacts very quickly over the next, say, one to two weeks,” he said.
The National Oceanic Atmospheric Administration’s (NOAA) Climate Prediction Center released its update Thursday. The temperature outlook for July indicates higher likelihood of warmer-than-average conditions in the month ahead.
“Almost the entire country is leaning towards warmer climate in July, with the exception of the northwest states,” Edwards said.
The precipitation outlook for July does not show a clear signal for either wet or dry conditions in South Dakota.
“Wetter conditions are favored to our northwest, and drier to our southwest, so we could be in a transition from a drier to wetter pattern in the month ahead,” she said.
If drier conditions persist, farmers will face a challenging situation, Edwards said.
“Corn acres are pollinating in early to mid-July,” she said. “It’s a critical period for corn — a time when farmers do not want their corn acres impacted by heat or drought stress because those stresses have a negative impact on yields at harvest.”
The long-range outlooks for the Northern Plains continue to favor wetter-than-average conditions for the months of July through September, Edwards said.
“Much of this year, we have seen strong swings from dry to wet, cold to warm and back again,” she said. “The climate computer models may be picking up on a transition to a wetter, warmer period in late summer, which could be beneficial for soybean growers especially.”
Although agriculture acres benefit from recent rains, the moisture brings with it increased weed and pest pressures, Edwards said.
“Now that there is sufficient moisture in the topsoil layers in most areas, the hayland, pastures and grasses will show some short-term growth and green-up as well,” she said. “But the climate outlook remains challenging for long-term growth through the summer.”
Wildland fire will continue to be a concern in the weeks ahead, Edwards said. She pointed to the large presence of dry or dormant grasses that can burn easily.
HISTORY REPEATING ITSELF?
The worsening Central Plains drought brings talk of the flash drought year of 2012.
However, the two years don’t yet lend themselves to easy comparisons, according to a U.S. Department of Agriculture (USDA) official.
“We can’t compare this to 2012 at this point,” said Dennis Todey, director of the USDA Midwest Climate Hub.
Todey, a former South Dakota state climatologist, offered his comments Thursday in a multi-state conference call.
“What happens with crops remains to be determined for the rest of the summer,” he said. “If this drought moderates, this hot and dry weather in early June could be a benefit for corn by pushing it at the same time that it’s developing its root system. It pushes the root system deeper as it looks for moisture and nutrients. It could be good, but it depends what happens after this.”
Gillispie agreed that this year’s drought is unlike 2012 at this point.
“The current situation is kind of different than what we saw in spring and summer of 2012. That year, there was a much longer period of much-below normal rainfall and much-above normal temperatures from March through September,” he said.
“(It) followed a period of above-normal precipitation, from September 2008 through February 2012. Soil moisture storage was very high prior to March 2012, so the onset of the drought impacts was slower than what would be typical in a flash drought.”
In some ways, this year stands to become worse, Gillispie said.
“This year, the soil moisture storage going into spring and summer was much lower than in 2012, so the impacts will be much quicker to develop if we go another 1-2 weeks with hot and dry conditions,” he said.
“Whether we see flash drought development, normal drought development or no drought development really depends on what kind of temperatures and rainfall we see in the next month or two.”
If conditions don’t improve, regions with drought could see even worse conditions, Todey said. Even regions currently without drought could see sudden changes.
“The corn could be heavily impacted by July, and the soybeans could be heavily impacted by August,” he said.
Gillispie offered some reason for optimism.
“There is still hope for not seeing any significant drought impacts if we can cool off and get some rain,” he said. “But our margin of error is very small now, thanks to the last few weeks.”
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