Severe WX April 12-15th, 2018 Severe Potential

KoD

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#1
The dates may change, but the Euro is focusing in on a potential severe threat in the long range. Since there's been some consistency and much discussion, we can keep it focused on this thread.

 
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#2
The dates may change, but the Euro is focusing in on a potential severe threat in the long range. Since there's been some consistency and much discussion, we can keep it focused on this thread.

I will be curious to see how the models resolve this over the next few days... some of the looks are downright scary!
 
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#5
One of those cases that if the Euro is right , despite the slp being farther north you still get southerly winds at the surface.

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It has to do moreso with the EXTREME depth of the low (Sub 980) than its positioning. We regularly get tornado outbreaks with surface lows up into Nebraska, Iowa, and even Minnesota (11/29/16)
 

ARCC

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It has to do moreso with the EXTREME depth of the low (Sub 980) than its positioning. We regularly get tornado outbreaks with surface lows up into Nebraska, Iowa, and even Minnesota (11/29/16)
Exactly. This will probably not be a case where the winds veer at the surface. In fact if last night's Euro verifies, surface winds probably back more than modeled due to another lobe of low pressure that may form to the south of the main low pressure.

Another notch toward a higher risk setup is the large pressure falls. The Euro puts a very large area under 1008mbs.
 
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#8
So as we look ahead, would next weeks system seem to stay in the Central US, or would we expect the southeast to be affected as well?
 
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#9
All of the local (HSV) stations are forecasting next week’s highs to be below normal. If that is the case, there would have to be a setup with a rapid temperature and dew point increase. Is that expected?
 
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So as we look ahead, would next weeks system seem to stay in the Central US, or would we expect the southeast to be affected as well?
That would cover a pretty large area... southern plains .... mid south.... parts Dixie. Lower Ohio valley least... course still a lot model watching to do ... table being set for something big... and perhaps a multi day event
 
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#11
All of the local (HSV) stations are forecasting next week’s highs to be below normal. If that is the case, there would have to be a setup with a rapid temperature and dew point increase. Is that expected?
This is more than 7 days out. There's no way to make any sort of reliable temperature forecast at that range.
 
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#14
I've been looking at those models that have run out to at least as far as Day 10. They all seem to agree that there will be a low pressure system somewhere in the central CONUS on Friday, but they disagree on the exact placement and intensity. Of all the models only the Euro ensemble comes close to the main Euro on both placement and intensity, and even then the low stays well above 980 mb. Nonetheless, it does still show a fairly tight pressure gradient over the eastern CONUS, so that should be something to watch out for.

Interestingly, the Euro models suggest that there will be a decently strong low (dipping into around the 980-mb range) moving through the Northern Plains on Thursday, with the Friday low spinning off immediately behind. So that would be two back-to-back strong low pressure systems tracking across the Northern Plains/Great Lakes region near the end of next week!

One could only imagine how things could play out if that does indeed verify...
 

ARCC

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#15
Looking a little closer at the 12z Euro, at 500mb winds quickly become almost parallel with the dry line vs last night's run which was much more perpendicular. While this run is more powerful as a system, last night's run would probably be a bit worse for the deep south.

Still lots to resolve concerning this possible event.
 

Taylor Campbell

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#16
So many different ensemble ideas, and model differences. I imagine a severe threat will take place during this time frame, but how bad it gets, and where exactly is very much up in arms.
 

ARCC

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#17
Latest model runs from last night through today is trending away from severe weather east of MS. Still a significant system for the Midwest, but not what it was yesterday or a few nights ago. In fact the Euro doesn't get the dry line east of Memphis and the GFS/CMC show the same vein of thought.

One thing to watch is what may come next should the above scenario take place. Most of the major tornado outbreaks had a large "priming" system before them. By hr240 on the Euro you have 72 degree dew points sitting on the gulf coast.
 
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#18
Latest model runs from last night through today is trending away from severe weather east of MS. Still a significant system for the Midwest, but not what it was yesterday or a few nights ago. In fact the Euro doesn't get the dry line east of Memphis and the GFS/CMC show the same vein of thought.

One thing to watch is what may come next should the above scenario take place. Most of the major tornado outbreaks had a large "priming" system before them. By hr240 on the Euro you have 72 degree dew points sitting on the gulf coast.
This is actually a system with two shortwaves. The leading shortwave is the one that's becoming a bit less amplified and that's the "primer" wave you're talking about. There's a second one digging into the rockies at 192 which is going to be the big one. It's overamplified right now, but I actually see that as a plus as the trends this year have been to deamplify systems as we get closer.
 

ARCC

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#19
This is actually a system with two shortwaves. The leading shortwave is the one that's becoming a bit less amplified and that's the "primer" wave you're talking about. There's a second one digging into the rockies at 192 which is going to be the big one. It's overamplified right now, but I actually see that as a plus as the trends this year have been to deamplify systems as we get closer.

The problem with the second system is the trend is farther NW with the trough and strengthening of the SE ridge. Like I said earlier, the dry line never gets east of Memphis on this run. Here are the last three Euro runs. Looks like the lastest Euro also slowing the system as well. Still a significant system, but a good bit less a threat verbatim for the SE.

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#20
The problem with the second system is the trend is farther NW with the trough and strengthening of the SE ridge. Like I said earlier, the dry line never gets east of Memphis on this run. Here are the last three Euro runs. Looks like the lastest Euro also slowing the system as well.

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The Euro is notorious for overamplifying things at this range. I'm not particularly concerned about it at this juncture. If anything, it's a good thing because that means that things may not be underamped at verification.
 

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