Key points of the forecast for the Southern Plains include worsening drought conditions in parts of the region due to well-above-average high temperatures in late July and early August; an expansion of moderate to severe drought in central Kansas and Oklahoma over the past few weeks; rains from Hurricane Beryl that spared the driest areas of Texas in July; and only short-term benefits from mid-August rains in Kansas and Oklahoma.
A similar situation is seen in the northern Plains, as shown by the U.S. Army Corps of Engineers’ forecast for flow in the Upper Missouri Basin north of Sioux City, Iowa. The USACE’s July report indicates that July flow in the Upper Missouri Basin was 2.8 million acre-feet, 15 percent below average. John Remus, chief of the USACE’s Missouri River Basin Water Resources Division, said in the report, “July brought warmer, drier weather to the Missouri River Basin. While there were storms in all states that brought small areas of above-average precipitation, overall precipitation in the basin was below normal.” The Corps of Engineers forecasts annual flow above Sioux City to be 23.9 million acre-feet, 7 percent below average. This winter’s river discharges from Gavins Point, South Dakota, are expected to be near the minimum level of 12,000 cubic feet per second.
This week’s weather conditions will bring more drought to the Southern Plains, with daily heat index highs exceeding 100 Fahrenheit in Oklahoma and Texas. The Northern Plains region is expected to see showers and thunderstorms, bringing at least short-term relief from dry conditions. However, according to the Drought Mitigation Center, drought is expected to either develop or intensify throughout August across much of the Northern Plains; and in the Southern Plains, drought is expected to either develop or worsen across much of Kansas and Oklahoma. The seasonal forecasts for the two regions through fall continue this combination of drought development and/or worsening in both regions.
The expected onset of La Niña this fall will play a key role in the dry outlook for the two regions. La Niña, the cold-water phase of the equatorial Pacific, correlates with below-average rainfall in the Great Plains, particularly the Southern Plains, during the fall months. How strong La Niña becomes and how long it lasts will be critical for winter wheat planting and early growth, groundwater supplies, and winter pasture and hay prospects.
Bryce Anderson can be reached at [email protected]
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