Strong-to-severe thunderstorms are expected through Sunday as a large upper trough shifts into the midwest today. A deepening low pressure center will shift into the central Plains today with a cold front extending southward. By Sunday, this low will shift to the north-northeast into South Dakota with the elongated cold front extending south to southwestward into Texas. This strong low pressure center is expected to set the stage for a multi-day severe weather outbreak across the Midwest, with the central Plains states of southern Nebraska, Kansas, and western Oklahoma the primary states under the gun today, and Iowa, Wisconsin, Illinois, and Missouri the primary states tomorrow.
Looking across the region this morning (3:00 AM), two separate lines of showers and thunderstorms exist. The first one currently exists in the Dakotas and Nebraska and is heading off to the north to northeast at 30 to 40 MPH and the second line existing over Nebraska and Kansas and traveling at a similar direction and speed. This is the biggest wild card in how things will setup across the Plains today in relation on how long these will last in that region. The current expectation is that these will either dissipate or move out of the area where storms are expected to develop in the later afternoon.
It is expected that instability and moisture will return to the Plains this afternoon as peak heating occurs. It’s important to note that the risk there is very conditional with what happens with the storms this morning, as mentioned. However, either way, the environment is very favorable for the development for severe thunderstorms, including very large hail, damaging winds, and strong tornadoes. Discrete cells are expected to develop over the Central Plains in the mid-to-late afternoon hours, when the tornado and large hail potential will be maximized, before things become more linear and present a damaging wind threat.
Locally, storms will likely not reach the state until very late (likely after 8-9 p.m.). These may have a few associated embedded strong-to-severe cells within it, but this line will likely be weakening by the time it reaches us and the severe weather threat should be minimal. Storms will continue pushing east through the early morning to daybreak hours with moderate to heavy rain anticipated.
Sunday’s forecast, like the recent event we had in the state, is very conditional in nature. There is a lot depending on what happens with the previous days storms. We saw it with the recent event that we had that things busted thanks to morning storms. What happens with the morning convection will basically determine what happens later in the afternoon. We’re currently expecting storms to be ongoing in the early morning hours Sunday as the line of storms from Nebraska moves through. However, there should be some destabilization along the dry line in the afternoon as peak heating happens which could trigger another round of storms. We will have to see on this as this is a fluid and rapidly changing situation. This would likely start out in the form of clustered discrete cells before becoming more linear later on. Like we said, we will have to see on all of this. The primary risks with this would be large hail and damaging winds.
Stay tuned to the Iowa Weather Network for the latest information!