The Storm Prediction Center in Norman, Oklahoma has posted an elevated risk of severe weather for today. A trough is currently moving eastward across the Central Plains into the Upper Mississippi Valley region. A cold front will extend off this trough, spanning across the Dakotas and into Kansas and Oklahoma. These features should arrive later tonight and be the forefront for thunderstorm development.

Current thunderstorms this morning across Nebraska are rapidly weakening and should pose no threat to this forecast. The wild card at play with this forecast is going to be cloud cover and if the state can get the surface heating needed to lead to instability. IR satellite data at 5:30 AM this morning showed a large area of clearing over eastern Nebraska with the trend beginning with nearby areas. This will be monitored throughout the morning and will be kept an eye on.

If the clouds can clear out, surface heating will likely lead to better instability, and when combined with the usual ample amount of moisture over the area, the environment should heavily favor thunderstorm development. Deep-layer winds along the low-level jet and some shear should lead to another all mode severe weather days, with large hail, damaging winds, and tornadoes all possible.

Storms are expected to begin in the mid-afternoon and intensify during the evening. Damaging winds will be the primary threat with the line that rolls through with large hail possible with the stronger cells across southwest Iowa. Flooding is also a concern, with river levels high and the soil still moist, all in thanks to recent rains. Storms should clear out overnight and lead to some clearing before a larger severe threat on Sunday.

Sunday is appearing to be a bigger threat than Saturday, even with two wild cards at play. Storms from today and how they will affect Sunday’s forecast is still up in the air. If storms fire later today, the forecast for Sunday can easily shift. However, with continued confidence in models, we are sticking with our current forecast.

Another shortwave moving through the area tomorrow, which should serve as the trigger for development. Previous day’s storms are expected to clear out into the east and lower Great Lakes region while stronger storm development is anticipated across the Upper Mississippi Valley. The Storm Prediction Center has posted an enhanced (30%) risk area for a large area of Iowa to denote this. With continued ample moisture, high instability, strong shear, and steep mid-level lapse rates, any storms in this highly volatile environment will be capable of supercells with all threats of severe weather possible.

The gunpoint right now appears to be centered on an area between Sioux Falls and Sioux City. Multiple discrete cells are expected to begin forming in this area in the afternoon and likely increase in coverage. The best chance for tornadoes will be when these cells first start popping up and utilize the strong shear available. By evening, these discrete cells are expected to transition to an organized severe weather threat with very large hail, damaging winds, and flooding all possible.

Those cells are expected to merge with another line that could form in eastern Nebraska. There is some uncertainty there as there would be some capping where additional development is expected to occur. If the cap breaks like expected, widespread and intense severe weather is possible along this line with an enhanced risk for damaging wind gusts during this period.

Storms are expected to move east into the state and continue with these threats through some of the overnight. Severe thunderstorm activity likely will continue as storms head eastward with renewed forcing favorable for continued thunderstorm development. The environment will still support storms in the morning Monday, which is the reason an elevated risk of severe weather has been also included with the Monday outlook. There will likely be no weakening with the Sunday system. The entire state should be aware of this threat. 

Stay tuned to the Iowa Weather Network for the latest information!

Henry Luker | Lead Forecaster