Verne,
Do you mean the 21st and the 22nd?
(might as well post all my thoughts in this thread tho)
I think the dryline will remain capped on the 20th, and even if a storm does form, deep layer shear will be marginal at best.
On the 21st, an initial impulse which swings around the digging longwave trough will move across the area. We could use some deeper moisture, but overall the setup looks pretty impressive with possible supercells developing along the dryline and propagating east at pretty chaseable motions.
On the 22nd, the longwave trough will amplify. We'll see how much it does, because if it amplifies too much 500mb winds will turn southerly and we get squall line vs. supercells. One thing seems likely (especially if the longwave amplifies over the Plains rather than over the Mississippi Valley) and that is there will deeper moisture.
Interestingly, the European model cuts the longwave off over the Desert SW, and the GFS Ensembles are divided over this issue. So this threat is not etched in stone yet.