Severe Weather Threat 12.26-12.29.2024

Georgia folks: FFC's AFD. TLDR: wedge breakdown for ATL metro, QLCS tornadoes and damaging winds late tonight into Sunday morning. Classic high-shear low-CAPE scenario. With a strong LLJ kicking in, it'll be helicity city, and anything that can get spinning could produce.

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Local NWS has me (upstate SC) in the clear till early Sunday when high-shear low-CAPE STS is predicted but I'm not so sure now.
 
Local NWS has me (upstate SC) in the clear till early Sunday when high-shear low-CAPE STS is predicted but I'm not so sure now.
I'd just go to bed prepared. You'll probably be out of the worst of it until early Sunday morning, but always better to be safe than sorry.
 
Past few runs of the HRRR really putting central MS in the hot zone. May be the area at greatest risk of truly discrete supercell development this evening into tonight.
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From the discussion

The corridor of greatest concern will be late afternoon
through the evening from central LA into central MS. Considered an
upgrade to HIGH for this area, but will maintain the ongoing MDT
after consultation with local WFOs.
 
I will say the potential for southern counties of North MS being included in a Level 4 risk are increasing.
 
The baseline for this event is unfortunately pretty high, in my opinion: We are likely to see a strong QLCS moving from E Texas all the way into Alabama/Georgia with the possibility for embedded supercells. The orientation of the line continues to trend more 'normal' to the wind shear vectors, which typically supports quite high levels of tornadic activity even for non-discrete storms.

In particular, the surface low and strong low-level shear will likely favor a corridor of enhanced tornado potential from LA into N MS. (I've highlighted this rough area in black, only a rough analysis though).

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That's just the floor, though - any discrete supercells have the potential to produce long-track EF3+ tornadoes (as the SPC stated). The environment will become very favorable, and the hodographs turning up on model soundings are quite reminiscent of quite a few long tracked violent tornadoes. Fortunately, the signal among CAMs for sustained discrete supercells is pretty weak at the moment, and it is quite possible in my opinion that all storms really struggle to get going ahead of the line and are quite weak.

The flip-side of that is the models do have quite a strong signal for cluttered warm air advection showers and general specks of precipitation - and this is in the background of a very favorable trough ejection for a tornado outbreak: Fast moving, compact, divergent yet not overly meridional, with the speed/vorticity maximum almost perfectly imposing itself over the warm sector. This makes me quite concerned that any weak showers/convection will have adequate support to properly mature and become potent supercells, even as instability wanes.

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In all honesty, I have no real idea what's going to happen with regards to the prefrontal/semi-discrete mode, but the fact its a conceivable possibility and has the potential for a high impact event means close attention needs to be paid. All this is on top of a likely powerful, fast moving, dangerous (nocturnal) QLCS. These are just my rough thoughts of an amateur enthusiast, so could be way off. Really hoping for the best for all those in the areas at risk. Hopefully things are excessively messy from the get-go and tornadoes are few and far between.
 
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