Bill, I'm not sure if you know how the dryline "moves" through the day, so I'll just quickly explain a bit... Drylines often set up with westerly and southwesterly flow aloft (downsloping causes lee-side troughing, which, given a surface high to the east, bring southerly / return flow to the Plains). Given the sloping terrain in the plains (higher elevations west, lower elevations east), the moist air is usually quite a bit more shallow to the west than it is in the east. For example, if there's a dryline near AMA-LBB line, the moist layer is usually much shallower in Borger, Clarendon, or Perryton, than it is in Dallas or Houston. So, when the sun comes up and insolation commenses, the air near the sfc near the dryline heats up and begins to mix with the air above. As this happens (mechanical mixing), the westerly flow aloft is transported down to the surface. This is what causes the winds to veer behind the dryline. At any rate, that is BASICALLY how the dryline propagates through the day. If there is an area of enhanced westerly flow aloft, there could be enhanced westerly flow transported to the surface. If you have southeasterly winds to the east of the dryline, and southwesterly winds behind the dryilne, you're going to get some degree of convergence at the dryilne. If you have the enhanced westerly momentum transfer, you can end up with enhanced convergence and dryline propagation.
It's worth noting that I believe that soil type gradients can play a signficnt role in dryline propagation. If you have plowed, dusty fields (which would likely result in more insolation being converted to sensible heating) north of some corn fields (in which more insolation would be converted to latent heating rather than as much sensible heating relative to the plowed fields), you will likely have greater vertical mixing to the north than the south. This will cause the dryline to propagate more quickly to the north (over the plowed land) than to the south. There are places on the plains where you have a signficant change in land use character / soil type, which would seem to be able to cause these dryline bulges. Granted, dryline bulges occur usually on the mesoscale, so we're talking about a large-scale soil type / land use change, not like five acres of corn fields next to five acres of plowed fields.
