Quincy

The I-20 corridor looks like it has potential for several more hours. The return flow is pumping unstable air back north. Hopefully more storms don’t take a beeline toward Birmingham...

I also wonder how closely they use HREF probabilities as a guideline. They usually don’t deviate far from that. That popped a small tornado driven high risk at 12z.

Surface winds are more backed up here, but low level flow is rather weak. I’m actually in NE MS “chasing” now, near the AL border. More like making a decision soon if I’m going to bail back to Oklahoma.

It’s still a bit early, but I agree with this, especially for the western part of the risk area, closer to the MS River. Sure, we have large CAPE and near-record lapse rates, but the wind field there is just about unidirectional now. I think that getting big CAPE and large hodographs in the Southeast is exceedingly rare. The writing was on the wall when midday SRH maps looked relatively modest, west of the MS/AL border. Farther east has been a different story. CAMs remain aggressive with the zone of messy storm modes breaking into semi-discrete storms. It could still happen, but we’ll see. The air mass is recovering over central MS, but low level shear would need to improve. Of course you had that one long track supercell go largely unimpeded on the SE fringe of convection.

50 knot low level jet core advecting across southeastern Louisiana. Low level instability increasing across Mississippi/western Alabama. 7-8 C/km mid level lapse rates in place. Very little convective inhibition left across Mississippi. Things are about to get real.

I wouldn’t write off the southeastern half of Mississippi yet. There has been a slight southeast trend with recent HRRR runs. Note that the axis of a boundary exists from roughly Jackson-Columbus-Huntsville with ongoing and soon to be new convection along and southeast of this boundary.

One thing to note is the ongoing conveyor belt across central/eastern Mississippi. The most ideal parameter space is progged to develop along and just southeast of this zone by midday/early afternoon. The HRRR has trended just a tick SE, zeroing in on central/eastern Mississippi into central Alabama. You can obviously have tornadoes elsewhere, but you can envision a scenario with several long track, strong tornadic supercells racing across this area.

Initial look at a couple 12z soundings. JAN needs some boundary layer recovery, but that won’t take long with this setup. LIX is already quite unstable. Look at that CAPE... One thing I have noticed from early morning data is that low-level lapse rates are not very favorable yet. Mostly <6 C/km. That means it will probably be a few hours at least until action really gets going. Probably midday? Possibly late morning.

CIPS analogs deep into weenie territory now, but the pre-frontal signal for long track tornadoes in the MS/AL vicinity has been very consistent. It also aligns closely to a blend of CAMs. I won’t mention the top analog, but I will say the forecast LLJ tomorrow at 00z is stronger than any of the 15 analogs.

Shawn Milrad tipped us off to the EML showing up via 00z sounding from LZK/Little Rock...

The 00z 3km NAM is either scary af, clueless or both. I cherry picked some soundings with 700-500mb lapse rates over 9 C/km with Tds in the lower 70s. Even area averaged soundings show lapse rates around 8 C/km with a small capping inversion. Important note is that low level lapse rates in this environment are marginal, in some cases <6 C/km. If the cold bias is correct, you’d have that tiny cap being obliterated. Is it overly simplified to say a HRRR/3km NAM blend is one of the scariest scenarios you could fathom? HRRR is messy with widespread convection, while the NAM is just a little bit too cool in the boundary layer, resulting in very little warm sector convective initiation.

Texas doing the day before the day things...

Dixie events aren’t usually driven by “fat” or large CAPE profiles. Interestingly enough, this event to expected to have both impressive wind profiles and climatologically large CAPE.

To clarify, I meant to suggest that you don’t want a weak cap with a myriad of outflow boundaries within that instability/shear environment. You can see “swarms” of supercells when there’s a weakly capped environment, in a case like this.

You would hope for a cap as well, given the fact that early day convection lifts north and could very well leave down multiple boundaries... that’s one of the key differences between a significant event and a super outbreak.

I’d say the range of scenarios start at being similar to last Wednesday and that’s hoping either it’s a convective mess or there is some sort of cap that tempers the warm sector... and higher end being a generational event. Hard to envision an evolution without at least a couple of intense, long track tornadic supercells. The wind profiles and lapse rates alone also suggest a much greater large hail threat than we saw last week.

Speaking of analogs, very clear signal (multiple runs) on either side of the MS/AL border area for significant, long-track tornadoes. (Based on prior events, but it is a mixed bag in terms of severity, as @Chinook mentioned.)

FWIW, GFS shows a broad area of >7 C/km 700-500mb lapse rates over 68-71F dew points. (yes, some of the area is under convection) You don’t see this very often this far southeast during a severe event.

Wednesday wasn’t a colossal bust. Sure, there wasn’t much activity over the western heart of the moderate risk, but several long track supercells produced numerous tornadoes over Alabama. Thursday was even more fickle. Remember that SPC produces probabilistic outlooks. Just because the “odds” of a tornado max out at one point does not mean that this is exactly where tornadoes will form. Tornadoes are microscale phenomena and very complex.

This is a time sensitive version of the PPF (practically perfect forecast): There is some debate that the CIPS PPF method isn’t the best. I’d reference Gensini’s enhanced version tomorrow, once it updates. https://atlas.niu.edu/pperfect

I feel like the large/significant hail threat with these events in the Southeast often end up underperforming. You just don’t get the steep lapse rates aloft very often in this area that you do across the Plains. Plus the thermodynamic profiles are moist with higher precipitable water values than you’d ideally see for significant hail soundings. 3/19/18 on the other hand... (very different type of setup)

The DDC flukey tor appeared to happen near the warm front/low intersection. It seems like we get at least 1-2 events a year where the main focus is over TX/OK and a seemingly random tornado spins off near Dodge City...

Core punched the Paducah storm. A lot of hail, but mostly sub severe. Followed it closely from behind for over a half hour and never saw anything conclusive. Just a raggedy, low cloud base. Looks like the severe threat with this event is ramping down. Quite a few rain-wrapped tornadoes, that I had no business getting close to.