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Severe WX Severe Threat 17-18 March 2021

12Z HRRR's UH swaths. Nasty.
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I know some high risks sometimes Forecasted Convective Amplification Deficiency, but i have a feeling this won’t be a Forecasted Convective Amplification Deficiency, the ingredients are really organized and unstable
 
I also can’t recall many events where we have widespread backed surface winds out of the SE over a large portion of the region. That will really enhance the low level shear in addition to the 850 jet trending stronger on the early 12z guidance.
 
Does anyone here think the 30 percent will rise to 45 if the ingredients become higher and more organized, i personally don’t immediately think, but it’s possible a change could be made later. We already have a high risk which is the highest risk so it really doesn’t matter, but 45 percent is very very high.
 
Fred Gossage said:
View attachment 7018
And with this environment...
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The only possible positive is that the mid-level trough is coming in more positively tilted on the 12Z HRRR, hence the PDS designation for the TOR threat has disappeared from some of these soundings at 12Z. 850-to-700-mb wind fields are more backed vs. 11Z and the LLJ is a bit weaker around 19Z today, despite even stronger instability due to the EML and diurnal heating. Aside from this quibble, everything else looks primed for a significant event, and localised boundaries could help offset the VBV issues, at least somewhat. But a more negatively tilted trough would definitely help this event achieve its penultimate ceiling.

Edit: the 12Z NAM has also trended more positively tilted with the trough vs. 06Z. Could this be a slightly good sign?
 
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Kory said:
I also can’t recall many events where we have widespread backed surface winds out of the SE over a large portion of the region. That will really enhance the low level shear in addition to the 850 jet trending stronger on the early 12z guidance.
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I agree, the low level turning is not just strong but very widespread...and not limited to just around the warm front.
 
NorthGaWeather said:
Just a quick nowcasting observation for the Georgia folks. The area of showers and isolated thunderstorms over west-central Georgia is really bugging out to the northeast. While this may momentarily re-enforce the wedge boundary in those areas, it will quickly be scoured through the afternoon/evening.
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Also this in the newest SPC discussion; even if you're not in the enhanced risk, don't count yourself out if you're in the west metro, these storms definitely won't care about the risk categories.
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Fred Gossage said:
New incoming 3k NAM has a widespread 50-55 kt 850mb jet spreading from south central MS up through north central AL during late afternoon peak heating...
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Also has a good bit of activity during the late afternoon with UH swaths, at least significantly more than in the 06Z run.
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Cool and overcast here (63°) but the clearing is coming... seeing 70s dews in south MS is just horrifying
 
Could the storm mode be a bit messier than expected because the latest HRRR/NAM show a more positively tilted trough vs. earlier runs?

I am just pondering aloud as to just what could hopefully limit the potential of this event.
 
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