Good afternoon everyone! A band of heavier showers and storms continue to progress northeast across northern NE into southern SD as of 12:40pm CDT. A few stray showers have also trekked into far southwestern MN/northwest IA. An earlier patch of showers/storms have pushed eastward across the state of IA with a slow weakening trend noted as the atmosphere where it is located (eastern IA) is more stable. Widely scattered convection is also making its way across southwest NE.
Here is an updated version of the Severe Storm Outlook from this morning’s update: A frontal boundary continues to slowly work south today and along this boundary is where we expect scattered storm development to occur. Steep lapse rates (change in temperature with altitude), high instability, strong vertical wind shear, and low-level moisture will all aid for storm development in an environment that is suitable for strong storms. An overnight severe weather threat exists with these storms. More information is provided in the graphic.
Shown below are timeframes for the probability of thunderstorms over the US. For our region, the areas circled in blue have the best chance for storms during the specified timeframe. Please feel free to click on the image for a clearer picture.
There is still some uncertainty between the different high-resolution models for the evolution of today/tonight’s storms. The SPC notes that a storm cluster could emerge from the morning convection across northern NE but details remain very uncertain regarding that at this time. One detail that is more likely is that a few discrete cells should develop over portions of western NE late this afternoon into the evening with a large hail and damaging wind threat before congealing into a possible MCS downstream across central/eastern NE late evening. If an MCS develops, the primary threat at that point would be damaging winds. Isolated tornadoes cannot be ruled out with this setup. The northern fringes of this storm activity will likely clip the southern parts of SD, giving them increased chances of severe weather. After 9pm CDT storm activity is expected to be pushing into western IA with upscale growth in storms across northern IA through the nighttime hours that also pose a severe risk. This activity should also build into far southern MN during this time with severe weather not off the table. Behind these disturbances, isolated/widely scattered showers/storms are expected to follow in western/central SD overnight. Simulated radar through 7am CDT Monday:
Here is an updated graphic for total rainfall through 7am CDT Monday: Numerous thunderstorms are possible during portions of the night over northeast NE and northern IA. Outside of the circled region in SD/MN, showers/storms will be more widely scattered overnight with up to a half an inch in localized spots.
If you have any questions do not hesitate to reach out and have a great rest of your day!