The National Weather Service has issued flood warnings for the middle of this week along the North Platte River above Lake McConaughy.
Citing “heavy and prolonged rainfall” in the watershed the river drains in Wyoming, the warning indicates that flows in the river could reach 5,000 to 6,000 cubic feet per second (cfs) on Tuesday and above 8,000 cfs by Thursday in stretches of the river near Mitchell, Neb. Water is being released from Glendo Reservoir in Wyoming as it nears the flood pool. On Tuesday, the reservoir was at about 98 percent capacity.
If the high flows materialize, the North Platte River above Lake McConaughy could reach a flood stage as high as 10.2 feet near Mitchell (flood stages vary at different locations due to channel width, depth and other factors), which would be near record highs.
At the Lewellen gauge, which is just above Lake McConaughy, the river is projected to rise to a flood state of 8.5 feet by Saturday, which according to NWS data, would represent moderate flooding at and near the gauge site. Estimates of flow rates into the reservoir were not immediately available.
However, high flows along the North Platte River below Lake McConaughy are not expected to be an issue. As of May 26, the reservoir’s elevation was 3,253.2 feet, which is about 12 feet below the maximum elevation of 3.265.0 feet. Inflows, although expected to rise this week, were at 3,500 cfs on Tuesday while outflows were around 300 cfs. In short, the reservoir has capacity to store the high inflows expected this week.
At the same time, flows in the South Platte River are beginning to decline in Colorado, although more rain could alter that picture. At the Roscoe and North Platte gauges in Nebraska, the South Platte is expected to reach a peak on Wednesday or Thursday before beginning to decline. However, the South Platte is projected to continue to carry higher than normal flows for the next few weeks.
Only minor lowland flooding is currently projected for the Platte River in central Nebraska.