Not sure about everyone else but I love getting into the post-mortem of an event and trying to discover why it did or did not perform as expected; now that the power's on, new phone is set up, and have a few minutes to look at stuff, it's interesting to dive in and see what we have via RAP and soundings...
It really does seem as though the combination of the warm nose aloft and extreme shear killed any prospective supercell updrafts across the AL/TN/GA corridor and will try to dive into why; major apologies if anyone else wished to also do so, feel free to still do that, more analysis is great
110kt flow at 500mb is absolutely insane; having that level of dynamics in the MS/AL/TN tristate area on the east side of the shortwave is in the very upper echelon of events here and we just don't see that very often - by all rights this should have been sufficient for a very upper end outbreak. This leads to
bulk shear of 90kt and
effective SRH of 600m²s² across parts of north AL by midday! Obscene dynamics in play
Usually in an environment of such extreme mid level flow, there isn't instability present, but surface CAPE was not absent on 3/3 - values of 500-1500 j/kg in fact were in place across the warm sector from central TN southward; on the surface this surface CAPE and such extreme shear would be extremely potent! However there was one additional factor...
The mid level warm nose is extremely evident on the RAP map of mid level lapse rates; values below 6 over nearly all of AL and GA indicate that updrafts would struggle massively upon reaching the 700-500mb level and vertical acceleration would become very poor in the warm air aloft. Updrafts that struggle with vertical acceleration also seem to struggle heavily in excessively high shear; the notion that weak updrafts are 'torn apart' by high shear while probably more nuanced than that by way of physics seems pretty accurate in the broader mechanics of things. Recall that we have 80-90kt of bulk shear and 400-600 m²s² of effective helicity in the vicinity of these horrible lapse rates; a weak and decelerating updraft dealing with category two hurricane levels of shear aloft. Supercells and tornadoes are surprisingly fragile and rely on subtle environments; the dynamics in play brought nuclear bombs to a knife fight
The morning sounding from BMX shows the insane dynamics but the warm air aloft in the form of a very strong cap is evident
The special 18z sounding, right before the QLCS hit BMX, shows that advection and sun had dramatically modified the surface profile with steep lapse rates in the lowest 1km, but look at that profile from 1km to 5km; the warm nose is still definitely present and lapse rates above the lowest 1km are terrible. Not to mention the mixing has kept the LCLs very high, above what one would prefer to see for supercell tornadoes. Wind profiles are still very strong but despite better surface thermos, the mid-levels tell the story - the strongly forced QLCS cares little for the meager lapse rates, but warm sector development relies extremely heavily upon it; the warm nose removed any chances of updrafts getting going ahead of the line, promising struggling weak vertical motion that gets sheared apart by the extreme shear present.
Thus, despite 78/67 and nearly 400 m²s² of 0-1km SRH - values which should indicate an extreme tornado outbreak! - the mid-levels tell the story, and provide the fine line between a QLCS day and a violent warm sector supercell outbreak