As of this typing its a late night at work looking over forecast models. Starting to get excited at the first real possibility of convection on Monday (04/21) here in Nebraska. While the better tornado/ severe weather threat lies well south in the Red River Valley region of OK and TX things are starting to look a little bit better for a shot at thunderstorms.
First of the WRF has a pretty strong 45kt 850 mb jet screaming into the region ahead of a stationary boundary/ coldfront and bringing with it the first true Gulf moisture of the season. A tounge of moisture extends just into the Southern tip of SD, emcompassing Eastern NE and points south across KS/MO/OK/ and TX. It also shows temperatures in the low to mid 70's and dewpoints in the lower 50's.
The GFS is a bit more moist. Especially at 850mb. It generates an LI of -2 in the KS/ NE border region south of Beatrice, NE at 00z on Monday. With a narrow tounge of CAPE.
NGM is a little farther north with energy across the northern plains., and also subtantsially drier/ more cutoff.
Either way if I wasn't working my Nebraska target would be south and west of Beatrice, although the real potential lies in the Red River Valley.