May 29: HIGH RISK in Iowa/Nebraska

6:25 PM Update: Several clusters of thunderstorms are currently affecting portions of southeast South Dakota, eastern Nebraska, and central Kansas. A line from approximately Kearney, NE to Grand Island, NE is currently being affected by a line of storms that are capable of producing tornadoes. These storms have had a history of producing tornadoes and may continue to do so as the night progresses. Additional thunderstorms are expected across eastern Nebraska, and western Iowa as we enter the nighttime hours. Currently, it is believe that the severe threat will continue late into the night, as the storms have the capability of tornadoes, large hail, and especially damaging winds. More updates are possible as storms begin to enter the state...

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The SPC has put areas of western Iowa under a high risk of severe weather for this afternoon, evening and even overnight. Other large portions of the state are under a moderate or slight risk for severe weather as well. Today's setup includes a warm front that is likely to be draped near the Missouri River Valley, a dryline across central Nebraska and a low pressure system in northern Nebraska or southern South Dakota. The combination of these surface features, along with warm temperatures and high dew points within the warm sector will combine to produce strong supercell thunderstorms. With wind fields being favorable for both low level shear and overall storm relative shear values, the risk of tornadoes is high. Storms should develop late this afternoon along the dryline in central Nebraska, with additional development possible along the warm front or other convective boundaries in the warm sector likely in the late afternoon.

Storms should move mainly east or northeast, typically between 20-35 mph. These storms should be able to remain discrete throughout the afternoon, evening and early nighttime hours. While remaining discrete, the risk of very large hail, damaging winds, and potentially strong tornadoes will exist across eastern Nebraska and northwestern Iowa. Overnight, storms will congeal into a large MCS, capable of producing strong damaging winds, large hail and the potential for tornadoes. This MCS will evolve over much of the state of Iowa during the overnight hours with these risks of severe weather.

This is a very dangerous situation that has been indicated by the forecasts, and by forecasts throughout the national weather service. People are going to be urged to pay very close attention to the weather as it may rapidly change and become increasingly dangerous. I will likely be out chasing in northwest Iowa, relaying reports to local officials if severe weather does occur. Hopefully we will have a safe day of severe weather across the area...