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Severe WX January 10-12, 2020 Severe Weather Forecast Thread

GA Stormchaser said:
Just looked at the 12z NAM and I would say things might be getting a little more "interesting" for North GA early into late evening on Sat.
The attached forecast sounding is for near Lake Lanier at 03z Sun. Models also show the broken line moving thru the area at that time with a forecast STP of 2.2. Also forecasted CAPE around 700.

Only odd thing are the winds between 9-12km.... is that what they call veer back?
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Correct that is VBV (veer back veer) but that’s way up in the wind profile. If it’s concentrated in the mid levels 500-700mb, then it’s more problematic and favors upscale linear growth of convection.
 
Kory said:
Correct that is VBV (veer back veer) but that’s way up in the wind profile. If it’s concentrated in the mid levels 500-700mb, then it’s more problematic and favors upscale linear growth of convection.
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Yeah, my thinking about the veer-back putting a ceiling on portions of this event has been with the soundings showing it between 850-500mb. Way high up it isn't too much of an issue.
 
CheeselandSkies said:
Yeah, my thinking about the veer-back putting a ceiling on portions of this event has been with the soundings showing it between 850-500mb. Way high up it isn't too much of an issue.
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I’m not seeing any issues with the wind profile further east on Saturday. Most actually look quite nice ahead of the QLCS in most of Mississippi and Alabama into Georgia. The trough begins swinging negative tilt which veers the mid level winds. I think if we can get a warm sector that’s modeled on the WRF guidance, there will be a solid tornado threat AHEAD of the QLCS.

We need to see how fast the QLCS is driven by cold pool processes.
 
CheeselandSkies said:
Early CAM output suggests the greatest supercell tornado threat with this event will be over southern MS/AL and the Florida Panhandle Saturday afternoon/evening, with lines up well with the forecast soundings and my thinking since yesterday that the most favorable shear profiles will be there.
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Instability will be greater there but shear profiles should be more optimum further north closer to the surface low where low level winds will likely be more backed.
 
Looooong time lurker here but have learned so much from this site, I’ve lived through plenty big OK tornadoes, enough to be totally freaked out anytime something as bad as this storm hits. That being said I’m in shreveport and have the opportunity to head south of I-10 near the coast of LA early tomorrow morning to a relatives house. Should I drive down or hunker down in Shreve? I’ve been prepared to hunker down for the last week. No storm shelter, just a nice big mattress over a bath tub setup in my house. TIA
 
TXLAOH said:
Looooong time lurker here but have learned so much from this site, I’ve lived through plenty big OK tornadoes, enough to be totally freaked out anytime something as bad as this storm hits. That being said I’m in shreveport and have the opportunity to head south of I-10 near the coast of LA early tomorrow morning to a relatives house. Should I drive down or hunker down in Shreve? I’ve been prepared to hunker down for the last week. No storm shelter, just a nice big mattress over a bath tub setup in my house. TIA
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Shreveport seems to be in the bullseye for tomorrow, so I would drive down especially if your relative's house is more sturdy and possibly has a basement.
 
TXLAOH said:
Looooong time lurker here but have learned so much from this site, I’ve lived through plenty big OK tornadoes, enough to be totally freaked out anytime something as bad as this storm hits. That being said I’m in shreveport and have the opportunity to head south of I-10 near the coast of LA early tomorrow morning to a relatives house. Should I drive down or hunker down in Shreve? I’ve been prepared to hunker down for the last week. No storm shelter, just a nice big mattress over a bath tub setup in my house. TIA
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Welcome :)
Other folks more knowledgeable than me will probably chime in, but statistically your "DRIVE" to a new place will be more dangerous than just staying at your current location IMHO. It's HARD to get hit by a tornado, so if I were you, I would just make sure I had good weather info and understand the warning polygon's and trust the polygon if a warning is issued. Sounds like you've already picked the best spot in your home, so your ahead of most.
 
Does anyone foresee the enhanced risk getting pulled further north? On some of the graphics I'm pretty much right on the line between enhanced and slight risk. Just wondering how the potential looks for the "sweet spot" to move further north over the Tuscaloosa-Birmingham corridor.
 
AL_ham_op said:
Does anyone foresee the enhanced risk getting pulled further north? On some of the graphics I'm pretty much right on the line between enhanced and slight risk. Just wondering how the potential looks for the "sweet spot" to move further north over the Tuscaloosa-Birmingham corridor.
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That all depends on how far north the warm sector resches with little or no contamination. Yes, I think it is likely it will be expanded north, especially for damaging wind threat...maybe for tornadoes too ...either way, the threat over that area is significant.
 
AL_ham_op said:
Does anyone foresee the enhanced risk getting pulled further north? On some of the graphics I'm pretty much right on the line between enhanced and slight risk. Just wondering how the potential looks for the "sweet spot" to move further north over the Tuscaloosa-Birmingham corridor.
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I was just looking through some of the models and I wouldn’t be shocked to see the main area pulled north. This is all predicated on an expansive warm sector ahead of the main line. Looking at the NAM it even has cells out in front of the line.
 
Richardjacks said:
That all depends on how far north the warm sector resches with little or no contamination. Yes, I think it is likely it will be expanded north, especially for damaging wind threat...maybe for tornadoes too ...either way, the threat over that area is significant.
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After looking at the models they seem to be trending up even into my area. Do you think the warm sector will expand far enough north to make it to TN for a tornado threat?
 
Xenesthis said:
After looking at the models they seem to be trending up even into my area. Do you think the warm sector will expand far enough north to make it to TN for a tornado threat?
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Southern portions of Middle TN will be closer to the main energy associated with this system but will have much less instability. Still, as has been mentioned several times, in cool-season events, things such as wind shear, be it changing direction with height, or speeding up with height (you'll have a little of the first and a lot of the second), could compensate somewhat for the lack of instability. I say that to say, yes, this time especially, I would say that areas even in the marginal list could see some spin-up tornadoes.
 
For Alabama/Mississippi, I think this is going to be a big wind maker for sure, I believe we will have a lot of power outages just with the gradient winds . As far as the tornado threat, if cells can form ahead of the squall line, then it's very possible. If the wind's are too strong, there is a possibility of the winds tearing the updraft apart and keep this to a wind event. Cape looks very low, but might be underdone by the models. If the timing is right, not seeing much of a tornado threat except embedded one's in the line for Mississippi due to the pre dawn timing. Things could change in the next day or so.
 
For the HSV area, from NWS:

One aspect that should be noted with this forecast is that many models are likely underdoing the warming that will take place (even with cloud cover) ahead of the main line of storms to the west. Expect the strong LLJ to pull up a warm, unstable air mass, with temperatures potentially rising into the lower 70s to accompany dewpoints in the mid 60s. Should this occur, we`ll likely have more instability to work with, fueling stronger and perhaps more significant severe storms. Combined with the very impressive shear/helicity, this would set the stage for more intense, rotating storms. Given that the deep layer shear is mainly parallel to the front, would expect a pronounced QLCS to approach the area by the early afternoon, spreading across North/Central Alabama in the 18-00z timeframe. One question yet to be resolved is whether there will be any discrete convection ahead of this line. The ECMWF and NAM show a pronounced negatively tilted upper-trough in conjunction with the deepening surface low. This scenario could allow for a least a few discrete convective cells ahead of this line if the thermodynamic environment is supportive. Given the intense speed shear and directional shear in place, this could result in a higher potential for tornadoes, including one or two that could be strong. Can`t stress this enough: it is critical for folks to be reviewing their severe weather safety plans now -- in the days before this potential event.

I believe this sums up the situation rather perfectly for the North Alabama area.
 
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