The Storm Prediction Center has outlined an area of enhanced severe weather potential on April 23rd, as the severe weather season finally begins to show signs of activity.
The SPC is discussing the presence of a corridor of instability aligned just east of a dryline set up along the western Central Plains, and it is this corridor of instability that is outlined in the graphic above. In these dryline situations, it is not uncommon to see isolated storm cells fire up, which then enhance the likelihood of tornadoes and overall elevated severe weather. If enough individualized storm cells form, the cells can congeal into a nasty squall line, or may just remain as individualized cells, which would maintain a raised tornado threat.
Model guidance shows this narrow section of instability, as the GFS model graphic above shows. However, under the roughly-15000 j/kg of instability (indicating the atmosphere is decently unstable), we see a hatched gray area. This indicates the presence of a capping inversion, which just means there is warm air above the surface that is hindering the development of thunderstorms. An analysis of a sounding chart confirms a layer of warm air in the first few thousand feet above the surface. The concern here is that this capping inversion may prevent storms from forming at all, which could just wipe out the severe threat. In this case, there is a severe weather threat if storms form; the question is just if these storms will form.