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Severe WX Severe Weather Threat - Jan 2nd - Jan 4th, 2023

Here's the full-run UH swaths from the 18Z run of the SHiELD model. I think I heard somewhere that the model has a tendency for overdoing things like UH but I figured I'd post it here for posterity.
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Man the 00z NAM really slowed things down. Its progression is slower than Euro and GFS. We'll see if this trend continues, but it seems we may have a daytime event in Mississippi on Tuesday. Monday is looking like a daytime event for East Texas and a nocturnal event for Arkansas/Louisiana Monday night.

Not what I wanted to see since Monday is a holiday and I have a free day off work.....but it is what it is. I wasn't planning on going that far West on Monday.

Need more runs. Maybe NAM is just off....
 
We'll see what comes from SPC tomorrow but I feel like the 30% is gonna get expanded a little east. Maybe not by a lot though. I can see where they have one for Tuesday if trends continue slower. Regardless outside of the potentially significant severe weather outbreak, the heavy rain/flash flood threat would probably end up being the secondary concern.
 
SPC already introduced "strong tornado" wording for Day 3 (Monday). Looking at NAM forecast soundings from the areas of greatest forecast EHI over east Texas, I see very strong low-level turning and high 3CAPE (>100 j/kg on some soundings), but also some veer-backing in the 700-500mb layer as @Casuarina Head alluded to earlier. IIRC this is the layer where it is known to cause problems for mesocyclone intensity/longevity (above 500mb it's not really a problem, or so I've read).

So my best guess (at that's all it is) at this point is, this could very well be yet another event where we don't see any really high-end, long-lived supercells producing large tornado families with EF3+ damage potential, but we could see a number of relatively short-track EF2-mid range EF3 tornadoes that could still be quite catastrophic/potentially deadly if they hit the wrong place at the wrong time.

Caveat: It appears this is also another setup where parameters peak overnight; this sounding from Arkansas at 06Z (midnight) Tuesday...yikes. 157 j/kg 3CAPE and >400 m2/s2 0-1 KM SRH is trouble despite the veer-backing.


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With the NAM slowing things down a bit for Tuesday, it puts parts of MS/AL in play for a possible tornado threat Tuesday afternoon. Previously it was looking like the cold front would become oriented SW-NE parallel to the mid/upper flow as the system occluded, with totally unidirectional winds on the soundings.
 
Sizable D4 outlook area, including Atlanta, Birmingham and Jackson.
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Sounding from Meridian, Mississippi area for Tuesday afternoon.
 
Edith said:
I’m frankly not that impressed. Looks to me like the tornadoes that do form will have a hard time staying down. I can honestly see this being a Forecasted Convective Amplification Deficiency which would be fantastic
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As I stated previously, I think that large-scale outbreaks with multiple, long-tracked EF3+ tornado families are (mostly) of the past. In a warming climate the significant events that do occur will tend to be more localised, isolated, and/or shorter-lived. In general, it will be quite difficult to get events like the past Super Outbreaks, Palm Sunday, Super Tuesday, etc. until the global climate shifts into a cooler state. Since 2012 very few events have come close to the major outbreaks of the past, other than Easter 2020 and 10–11 December 2021, the latter of which did feature classic, long-lived EF3+ families but was more geographically restricted than some of the other big events that I mentioned.
 
KevinH said:
It will be interesting to see how if and when this risk area is modified in coming days.
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In the immediate time frame, definitely not something to sleep on for MS/AL/GA. We all know how Deep South winter events can behave.
 
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