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

CheeselandSkies said:
I disagree. The pronounced veer-backing of the vertical wind profile displayed in forecast soundings argues against long-lived tornadic supercells. QLCS should nonetheless be capable of producing widespread damaging winds and embedded tornadoes, some possibly strong. SPC however is unlikely to high risk without a classic, steadily veering with height wind profile.
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There are some great looking hodo's across MS during this timeframe. However, this event was never going to be a classic dixie tornado event. I imagine there will be some long-lived tornadic supercells embedded within the line or ahead of it (especially along and south of I-20)
 
NorthGaWeather said:
There are some great looking hodo's across MS during this timeframe. However, this event was never going to be a classic dixie tornado event. I imagine there will be some long-lived tornadic supercells embedded within the line or ahead of it (especially along and south of I-20)
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I was referring specifically to parts of eastern Texas where the highest instability is progged for tomorrow. I agree the wind profile does look better for supercells across MS on Saturday. Winds are still fairly unidirectional above 700 mb but at least they don't sharply back with height from 850 to about 500 mb before veering again. I agree the low-level (below 700mb) turning and speed shear is eyebrow raising.

Another thing I noted is while the wind profile at mid-to-upper levels is fairly unidirectional, winds still maintain or increase speed with height. Weak winds at upper levels are a red flag for storms that rain into their own updrafts/have a cool, wet RFD that hampers tornado production.
 
We might have non thunderstorm winds that will at least require a wind advisory if not a high wind warning given the parameters.
 
What's the general consensus on the strength of the capping inversion tomorrow? Too early to say? That would help limit some of the supercell potential ahead of the line unless we get some gnarly cells right off and they break down the cap early.
 
CheeselandSkies said:
For some reason, I can't attach the sounding I want to the post above. It appears to upload, then a line appears through the filename and it doens't post.
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Typically means it is too big or the file isn't supported. Shoot me a PM and we will work out the issue.
 
The 12z nam is now beginning to come around to the higher temps and Td's strentching northward, now the Td at 65 in BHM just before the line comes in....this is higher than before It has the surface temps up to 67, in reality, will probably be closer to 73..surface based cape should be in the 500-1000 j/jg which will be plenty. It is obvious that the warm air advection will be screaming.
 
Still a large discrepancy on the WRF modes and NAM. Larger warm sector on the WRF models due to different handling of dew points and temps.
 
Is there any realistic fly in the ointment that could inhibit this threat into Alabama? It appears that there won't be coastal convection.
 
RollTide18 said:
Is there any realistic fly in the ointment that could inhibit this threat into Alabama? It appears that there won't be coastal convection.
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Not really for a linear system, widespread damaging winds appear likely from that. Supercell/strong tornado risk depends on warm sector quality and expansiveness...there are some questions to that regard
 
Moisture, Dewpoints, and temps returned overnight on a strong south wind. There should be a large, warm airmass moving eastward today.

Austin Executive Airport (KEDC)
Lat: 30.39°NLon: 97.56°WElev: 616ft.
ovc.png

Overcast
68°F
20°C
Humidity83%
Wind SpeedS 16 G 23 mph
Barometer30.03 in
Dewpoint63°F (17°C)
Visibility9.00 mi
Last update9 Jan 10:35 am CST
 


Latest from Fort Worth NWS depicts supercell development around noon, a bit earlier than expected and with little mention of a cap in place. They posted a prior update to this around 7:45 AM and since then they have noticeably increased the tornado potential.
 
MattW said:
It's going to be borderline for Atlanta I think. If it comes in just a little faster, it'll be worse, if it comes in just a little slower, it'll just be rain and thunderstorms. There's still the threat of damaging winds and embedded tornadoes, but like I said before, it won't be nearly the story from out west.
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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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Also just saw that BHM increased their Tornado confidence factor from 3 to 4 on the HWO graphic (not sure when that happened).
 
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