Yesterday I took a look to the maps and it seemed that there was a low pressure in southern Nebraska. Today things have changed a little with less low level back winds even though it remains a good line of convergence in Nebraska. Thermodynamic parameters remains so good with more than 3000 of Cape spread in a huge zone.
So far there's only a thing that I don't like: the disposition of storm motion vectors and 0-6km shear vectors that appear to be more favorable for linear convection.