Now that we are closer to tomorrow's threat, we can hone in a little more than I did the other day. First off, check the first map below which shows SPC's risk areas for tomorrow. We still have a lead shortwave which veers winds in its wake tomorrow, and keeps the low level jet a little on the weaker side, though probably not as weak as last week's system saw initially. Still though, despite the veered LLJ, the surface winds look to have a more southerly component, which would give a decent 0-1 km shear vector, which for a tornado outbreak is the most important shear layer. I agree with SPC's moderate risk, but despite robust moisture and more than sufficient instability progged, you can color me skeptical on this being a "major outbreak" of tornadoes. I will preface this comment though by saying that if you live in the risk area, be ready! This stuff can be tricky and you don't want to be caught downplaying an event that has any potential to turn out serious.
But I will look to the past some here. The second map below is the progged 500 mb map for tomorrow afternoon. Note the strong, but sharp, and already trying to tilt negatively, shortwave headig toward the South. My reason for some skepticism is that such a pattern looks conducive for storms to fire early, and with stronger forcing due to tilt of trough, we get many storms that can more easily cluster together rather than discrete storms which in a sheared environment can be more of a tornadic problem. If you look at historical data, many (but to be fair, not all) of the big outbreaks in the south occurred with a trough that had a larger base and / or was actually more of a positive tilt variety. Why? Well, since the South almost always has a lot more moisture to work with, positive tilt means forcing isn't as strong, but still strong enough for isolated / discrete storms to fire. The third map below is from 4/7/06, which was one such major outbreak, but I could provide other examples.
In any case, as mentioned, I agree a moderate risk is warranted. I don't see it being a high risk day, or at least verifying as one at this time, and think the tornado threat will be confined mostly to initial storms in western half of moderate risk area, and then become mostly a wind / hail threat rather quickly, with spin-up tornadoes mixed in the clusters still a possibility. We're still 24 hours away though, so small scale details can still change, so stay tuned! Maps referred to above follow:
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