A projected strong La Nina weather pattern this winter could worsen already dry conditions by next spring’s planting, a climate specialist says.
During a webinar Thursday, Iowa state climatologist Justin Glisan said a La Nina usually brings warmer, drier weather. However, the system also remains highly unpredictable.
Given that uncertainty, any moisture received now won’t impact remaining harvest but will play a critical role next spring.
“We need the moisture to recharge the subsoil going into the next growing season,” he said.
According to the U.S. Drought Monitor, all of southeast South Dakota and northeast Nebraska is classified as abnormally dry or in drought. In addition, prolonged wind gusts have created evaporation and further dried out the region.
South Dakota farmers have completed harvesting corn and soybeans, while Nebraska farmers are nearly finished, according to the U.S. Department of Agriculture (USDA).
This year’s drought conditions make it difficult to build up moisture for next year, according to Doug Kluck with the National Weather Service (NWS) in Kansas City.
“It would take a sustained effort on the part of the climate to recharge the soil, especially the lower part of the soil,” he said.
In that respect, the Great Plains benefited from saturated soil created during last two wet years, including the 2019 flooding, Kluck said.
“The entire region was so wet in 2018 and 2019, it may take about all of that moisture to help us get through this year, when it really turned dry,” he said.
This year’s harvest saw two sets of extreme temperature swings during October, Glisan said. The region went from records highs to record lows in a matter of days.
Looking ahead, the outlook calls for a strong La Nina weather pattern coming off the Pacific, which is likely to continue across the Northern Hemisphere this winter, Glisan said. The La Nina appears to contain staying power, with a 95% chance of remaining from January-March and a 65% chance from March-May.
“We see more variability with the La Nina than the El Nino (weather pattern),” he said. “We could see this La Nina sticking around into springtime.”
Once the La Nina arrives, it’s hard to predict its impact, according to Dennis Todey, director of the USDA Midwest Climate Hub.
“One caveat is whether La Nina will behave itself and act like we expect it, but that’s not a guarantee,” said Todey, a former South Dakota state climatologist.
The soil moisture will also be affected by the snow water equivalent (SWE) on the plains and in the mountains, Todey said. The SWE is the amount of expected moisture from melted snow and other precipitation.
Yankton received about six inches of snow during one storm last month. Other parts of the region received similar amounts of snowfall from the same event, but Todey noted any snow has largely melted from the plains.
The lack of plains snowpack allows temperatures to remain warmer than if the ground was blanketed, Todey added.
On the other hand, he’s monitoring mountain snowpack which could find its way into the Missouri River basin this winter and next spring.
“From Colorado and into Wyoming, the snowpack has started to form in the mountains. Some parts of the Rocky Mountain basin have snowpack 150-200% of normal,” he said. “This gives us an idea, moving into springtime, of the amount of runoff we could get from melting of the snowpack itself.”
The amount of snowmelt could create plains flooding but it could also impact the Missouri River basin, Glisan said.
The Gavins Point Dam releases near Yankton currently stand at 34,000 cubic feet per second (cfs) and will be adjusted as needed to meet the downstream navigation targets, he said.
The Missouri River mainstem reservoir storage stood at 56.7 million acre-feet (MAF) this week, Glisan said. The reservoirs remain in good shape to handle runoff, he added.
“It’s above the 1967-2019 average and below the maximum, within where we expect it to be,” he said. “It’s slightly above average, but not so much that there are any concerns.”
This year’s lack of precipitation has affected the ability of moisture to infiltrate the soil, Glisan said. “When we do get moisture, it’s harder to get down deep. It stays on the surface, which makes it easy to evaporate when the warm and windy days come,” he said.
Dry soil will freeze faster, which creates another concern, Glisan said. However, farmers won’t face inundated fields which hinder their ability to work the soil, he added.
“The silver lining is that we’re moving into a growing season where it makes field work and planting easier,” he said.
The seven-day forecast calls for light precipitation, Glisan said. The 8- to 14-day outlook calls for above-average temperatures. The long-range outlook calls for above-average temperatures and below-average precipitation.
Kluck cautioned against reading too much into certain factors at this time of year. More will be known as the region moves into winter and spring, he said.
“These are adjustments to the climate patterns, not the climate pattern,” he said. “There are 20 other pieces to the puzzle daily, weekly, monthly and seasonally based. They all come into place to form a forecast.”
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