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Severe WX April 1-2 (overnight) Severe Weather Event

What working my way through this thread today feels like.
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In all seriousness, though, confused not so much by the High Risk as much as the placement of the risk contours? Scratching my geek head here. We've got OWS supercells modelled WAY out to the east of the front, and the gradients for the risks are the tightest I think I've ever seen them on the eastern extent of a high risk? Very confusing situation, and the Broyles Effect probably is no small part in that. Very clear that the risk for supercells probably reaches into the northwestern 1/3 of Alabama, and there should be risk expansions there. I see some of the other CAMs aren't on board with the idea, but not even having a Marginal Risk for much of western Alabama seems like a bizarre choice.
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lake.effect said:
Can a pro (Andy, JW, Fred) help us understand what the SPC might be thinking with these somewhat odd risk contours?
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They are going for where the storm coverage is likely the highest, which plays a crucial role in verification. Whether the tornado probabilities verify given issues with storm mode is questionable, however.
 
andyhb said:
Just going to point out that the HRRR is probably overmixing later over the eastern part of this. For instance, it is trying to mix dewpoints in N/central MS down to the mid 60s when there are 70s dewpoints upstream with filtered sunshine as opposed to full sunshine. It is trying to get temperatures in MS/AR/TN to at/near 90 degrees.
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85 and clearing somewhat in Pine Bluff, AR at this moment
 
andyhb said:
Just going to point out that the HRRR is probably overmixing later over the eastern part of this. For instance, it is trying to mix dewpoints in N/central MS down to the mid 60s when there are 70s dewpoints upstream with filtered sunshine as opposed to full sunshine. It is trying to get temperatures in MS/AR/TN to at/near 90 degrees.
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I had to quote this and bring it over to another page. This is spot on.

Paying attention to what the atmosphere is actually doing and showing you, then one having a conceptual understanding of that and the associated processes, can easily help you find where models are dead wrong. The morning sounding from LZK showed a great environment...but I doubt many looked at SHV/LCH - JAN/LIX to see the character of the upstream airmass. The upstream low level airmass that is being advected in is sufficiently deep and very moist. Even if temps warmed into the mid 80s, the moist layer below that inversion will maintain a rich low level moisture profile.
 
I know tornadoes are the headlining part of this event, but the flooding threat still looks to be monstrous. 4 days of MDT+ flooding risks in a row across the same areas.
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I do believe Arkansas will mix out to some degree, but when you have 70s dewpoints with deep moisture profiles upstream and to the east, I don't think the whole event down south is going to be as dry as the HRRR is wanting to suggest.

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The HRRR is already mightily struggling with temperatures in the short term, likely due to poor handling of warm sector clouds. This plot shows that the 13z HRRR is too warm over much of the southern risk compared to recent obs (red colors).
 
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