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Severe WX Severe Weather Threats 1/21-1/22 2017 (Saturday - Sunday) (1 Viewer)


stebo

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Eastpointe, Michigan
GFS also jacked the surface temps up this run, 74 at Montgomery by 18z on Sunday. That is more realistic than the upper 60s it was showing.
 

Kory

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Tuscaloosa, Alabama
Now, the big question becomes the warm front and it's northerly extent. At this range, it'll be hard to resolve and probably won't get a handle on that until we're in the mesoscale range. But the jet dynamics with this system are nothing to play with and south of the warm front will have a loaded warm sector. It's just where it lines up. We've seen thermal boundary driven events in this state. Northern half is in a cool rain and the southern half has a risk of severe weather.
 

Taylor Campbell

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Wedowee, AL
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The forecast continues to vary quite a bit. I'm interested to see what models show come Thursday and Friday when the energy noses itself into the west coast.
 

Kory

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3,314
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Tuscaloosa, Alabama
The forecast continues to vary quite a bit. I'm interested to see what models show come Thursday and Friday when the energy noses itself into the west coast.
Timing alone is varying at 4-5 days out, in which the models are slowing the ejection of the 500mb jet streak, indicating more of a Saturday threat for the Lower MS River Valley and potentially nosing further east and a larger scale severe threat daytime Sunday for places east of the MS River. Then, add in the warm front progression from the Gulf Coast on top of trough evolution still varying run to run and there is still A LOT of uncertainty. That is why the SPC precluded the addition of a 30% contour which will likely be added in the coming days given the models continue showing the potential for a significant event.
 

Richardjacks

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510
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Hoover, Al
Timing alone is varying at 4-5 days out, in which the models are slowing the ejection of the 500mb jet streak, indicating more of a Saturday threat for the Lower MS River Valley and potentially nosing further east and a larger scale severe threat daytime Sunday for places east of the MS River. Then, add in the warm front progression from the Gulf Coast on top of trough evolution still varying run to run and there is still A LOT of uncertainty. That is why the SPC precluded the addition of a 30% contour which will likely be added in the coming days given the models continue showing the potential for a significant event.
It is interesting to see how the 12z GFS is trying to pick up on some mesoscale features. For example, the 997mb low that pops up west of Nashville, this suggest to me that this is some kind of warm front with a surface trough...notice how the 60+ td's are as far north as central Tennessee. South of there EHI is exceeding 2.0.
 
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78
Location
Center Point Alabama
Timing alone is varying at 4-5 days out, in which the models are slowing the ejection of the 500mb jet streak, indicating more of a Saturday threat for the Lower MS River Valley and potentially nosing further east and a larger scale severe threat daytime Sunday for places east of the MS River. Then, add in the warm front progression from the Gulf Coast on top of trough evolution still varying run to run and there is still A LOT of uncertainty. That is why the SPC precluded the addition of a 30% contour which will likely be added in the coming days given the models continue showing the potential for a significant event.
I also believe as we get closer they will have to move that area north perhaps at least as far north as U.S. 278 but at least to I-20
 

ARCC

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382
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Coosa county
One thing to watch is where the high and low pressure sets up over the Atlantic and the track of the low of the system itself. Yesterday on the GFS the high was stronger and in better position and the low was farther west. This allowed more ESE wind direction more dry air to filter in. On the 6z GFS, a love of the low pressure area is expanded eastward and the high is farther NE. This allows a much more SSE to south wind direction which would pump in higher DPs.
 

Lori

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I agree I-20 is a good spot the map to draw a line .
You know that's why I-20 was built?! So we could base everything above or below that line weather wise!:rolleyes:

Seriously, I'm a little worried, it's January and it's been almost 80 in a good part of Alabama....strong lows with cold fronts along a warm front line...I hope this doesn't get dangerous!!
 

Richardjacks

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Hoover, Al
I could see a focused area of surface convergence setting up around I20...this could be where the low level shear and instability line up...however, there may be an opportunity for the low level convergence to move further north away from the higher instability...again, mesoscale features that we are still days from figuring out.
 

Lori

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I could see a focused area of surface convergence setting up around I20...this could be where the low level shear and instability line up...however, there may be an opportunity for the low level convergence to move further north away from the higher instability...again, mesoscale features that we are still days from figuring out.
Richard, do they usually put out EHI predictions that early...the 2.0 and higher worries me but again, I understand we're still days away!
 

Kory

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Tuscaloosa, Alabama
GFS is a one/two punch. First, with the warm front Saturday evening and overnight as it lifts into Central AL. That would be a doozy if the LLJ responds more than the models are showing. Then, as the main trough kicks out Sunday afternoon. LLJ ramps up again with a surface low over NW AL with great thermodynamics.
 

Richardjacks

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Hoover, Al
Richard, do they usually put out EHI predictions that early...the 2.0 and higher worries me but again, I understand we're still days away!
The EHI is coming from the GFS...I wouldn't put too much stock in its location, just the idea that it has been showing this now for several days in late January is quite impressive.
 

Richardjacks

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Hoover, Al
GFS is a one/two punch. First, with the warm front Saturday evening and overnight as it lifts into Central AL. That would be a doozy if the LLJ responds more than the models are showing. Then, as the main trough kicks out Sunday afternoon. LLJ ramps up again with a surface low over NW AL with great thermodynamics.
One thing about winter severe weather events I have noticed is that the strongest storms aren't able to thrive right in the "belly" of the low. In other words, there needs to be some space from the surface low. For example, if I remember correctly, during the January 24, 1997 tornado in Tuscaloosa, the surface low was up in Missouri...not really sure there is anything to that rule, just something I have noticed over the years.
 

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