2025-03-14 EVENT: MO/AR/IL/IA/TN/MS/LA

[Dan Robinson]

We finally have some agreement in various model depictions of Friday's event as the main upper trough ejects and its attendant strong surface low spins up and moves northeast. As was feared initially, the influence of the preceding wave's departure will prevent high-end moisture (above 60F) from making it much farther north than the Interstate 40 latitude. A weird cut-off blob of moisture from the previous wave is shown lingering, but it is drifting too far east to enhance the target convection. In addition to the lack of moisture, another major negative is the mostly boundary-parallel flow aloft. The typically-favored surface low arc of storms (in central Missouri back northwest into the core of the low) will suffer from that, with models depicting a forced squall line moving at race car speeds. The translational speed of the line eastward is shown to be around 50mph: it's at Booneville Missouri at 21z and already in St. Louis at 00z. Individual cells/mesos in the line will be rocketing northeastward at 60 or 70 mph.

I would favor the first discrete cells early in the afternoon the farthest northwest you can get with any meaningful instability, closer to the coldest temps aloft and closer to the vorticity-rich surface low. As it's shown at this point, that looks like southwest Iowa/northwest Missouri and maybe even a touch west of there. My feeling right now is that window will be too short to be worth the drive from here, given the prospect of Saturday action to the south. My plan at this point, barring major change, is just to shoot lightning here with the squall line as it blazes past.

 

[William Monfredo]

the influence of the preceding wave's departure...forced squall line...shoot lightning...

I figured you might. There's some weather pictures to be had with this powerful system. Damage pictures too, as a nerve-wracking night's on the table for people under the threat of night-time, forward-flank tornadoes Friday near & after sunset. And the next day, secondary low pressure around Memphis keeps the threat going in the Southeast. As an aside, my jarring, night-time event was an F2 tornado that went over my Mid-City New Orleans apartment in the pre-dawn hours one February night sounding like the buzzing of 1000 bees. It really sounded like that.

 

[Dan Robinson]

There has been some slight improvement in northward moisture transport during the 06-12z model cycles, the NAM being the most optimistic (and the outlier ATTM) with the 60F line making it to I-64 after 00z in central/southeast Illinois. All of the others show a more solid, albeit narrower, swath of mid to upper 50s at that latitude. Wind profiles have improved in the low levels, with some workable turning below 850mb. If the outlier NAM is to be believed, southern Illinois could be a solid player, albeit after dark.

I fear staying ahead of things may be a challenge. Basically I-64 or I-70 are the only real options, with short 1-3 minute stops at exits. Going through a town or even a construction zone slowdown could be chase enders. Once the line gets ahead of you, you're not getting back in front (such is the case for most early season mega-trough events).