Operational and ensemble runs from the GFS and ECMWF have consistently indicated a huge longwave trough moving eastward over the Central U.S. during this time frame.  Embedded within this large-scale trough will likely be at least a couple vort maxes, one of which looks likely to eject out into the Plains on April 25, and another right on its heels on April 26-27.  Specifics are lacking at the moment since we're still 6+ days away, but the large-scale pattern is highly suggestive of a major seve