Severe WX Severe Weather Threat 10/31-11/2

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#1
Its officially spooky week, which also marks the unofficial beginning of the Dixie Alley cool severe weather season and we have certainly some spooky weather to track.

A potent and, if current trends continue, potentially significant severe weather threat exists for MS, AL, and TN as early as very late overnight on the 31st but with the most likely timeframe occurring sometime on the first. A large, lower amplitude trough embedded within a highly energetic Polar Jet stream will traverse across the region, bringing potentially a significant severe weather threat to track with it.



At the lower levels, a very troublesome LLJ looks to be brewing, and this will certainly be generating plenty of low-level shear in the atmosphere, as well as a surface low predicted to track just NW of the region (and it has been trending further NW which is putting more regions in play...)





Still early, but this is a fairly significant severe weather episode that will be needing close monitoring.. this is the Dixie Alley cool season after all, and these can spring up some nasty events from time to time. Still too early to make definitive calls, but this could be a substantial threat if trends continue the way they have over the last 36-48 hours..
 

Taylor Campbell

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#4
Still a lot of volatility in this period due to a recurving typhoon.
Yeah, there’s still a large spread among ensemble members with differences in timing, strength, orientation, and placement of jet energy. However, the general idea is for a severe weather threat during this period. How bad, exactly when, and who gets the worst of it is still to be determined. The EURO, and its ensembles are more aggressive than the GFS. I’d watch this one closely because it does have the potential to be a high ceiling event. It just needs to trend that way for it to be likely.
 
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#9
Well, 12z guidance ramps it up after 00z and 06z ramped down.
Tonight's 0z GFS keeps ramping it up.. sfc low at 998 now as it passes into TN with a VERY strong LLJ.. correct the thermo biases and the fact that its potentially too fast with the timing.. this is starting to smell like trouble.
 
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#11
Tonight's 0z GFS keeps ramping it up.. sfc low at 998 now as it passes into TN with a VERY strong LLJ.. correct the thermo biases and the fact that its potentially too fast with the timing.. this is starting to smell like trouble.

I'm getting that feeling too after seeing the Euro and GFS today. I imagine I'm not the only one waiting to see what the 0z Euro shows.
 

Taylor Campbell

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#13
Hmm. The operational CMC, and UK along with a large amount of EURO ensembles, and a few GFS ensembles support the idea that the energy comes in slower, and a surface low deepens further west. This scenario would really help enhance the severe threat for many because the time of day would be late morning into the afternoon, and also more areas will experience the strengthening low-level wind field. This has always been a potential, and it has not got lost nor trended away from it, but actually more towards it.
 
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#14
Hmm. The operational CMC, and UK along with a large amount of EURO ensembles, and a few GFS ensembles support the idea that the energy comes in slower, and a surface low deepens further west. This scenario would really help enhance the severe threat for many because the time of day would be late morning into the afternoon, and also more areas will experience the strengthening low-level wind field. This has always been a potential, and it has not got lost nor trended away from it, but actually more towards it.
These systems typically do slow down as models get a better handle. I fully expect this to trend towards an afternoon event on Thursday.
 
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#15
Severe weather threat continues after 12z and 18z model guidance is in. Potentially a higher end event is still on the table across MS, AL, and points eastward.. thermodynamics and shear continue to be on the uptrend and the possibility of a fairly strong EML ahead of the system as well as potentially multiple waves of broken lines of storms (some supercellular) overnight into the morning of the first could be possible.. this is going to have to be watched closely.
 
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#16
Severe weather threat continues after 12z and 18z model guidance is in. Potentially a higher end event is still on the table across MS, AL, and points eastward.. thermodynamics and shear continue to be on the uptrend and the possibility of a fairly strong EML ahead of the system as well as potentially multiple waves of broken lines of storms (some supercellular) overnight into the morning of the first could be possible.. this is going to have to be watched closely.

Just curious, where do you see the possibility of an EML ahead of this system?
 
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#18
00z guidance, especially the Euro, keeps this a larger threat due to the overall slower evolution of the system. It would likely be a midday Thursday threat compared to early morning of other models.

One thing for sure, storm mode looks cellular NOT linear.
 
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#20
A slower version of the 6z NAM would be very worrisome. It's bad enough as is but bring that in at midday instead of early-to-mid-morning with those dynamics in place? Yikes. Guess we'll see if the new run speeds things up here in a minute.
 

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