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Severe Weather Threat May 20-21, 2025

zath said:
Seems like a lot of tornado warned storms but few if any tornadoes. Plenty of storms "look" like they will do something (wall clouds, rising scud, etc..) but nothing is really making it to the ground across TN/MS/AR. Plenty of low level moisture over the area causing some very low cloud bases, so my guess would be a lot of these warnings are being driven by small-scale interactions with the hilly/mountainous terrain that is causing some elevated low-level rotation, but never enough to actually form a proper meso and tornado.
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Yeah and then things go apesh** after 6-7
 
Despite the supercells, SRH is still meager in the lowest levels. This is expected to change, and I reckon we may see an uptick in tornadic activity in the coming hours.
1747775052031.png
 
zath said:
Seems like a lot of tornado warned storms but few if any tornadoes. Plenty of storms "look" like they will do something (wall clouds, rising scud, etc..) but nothing is really making it to the ground across TN/MS/AR. Plenty of low level moisture over the area causing some very low cloud bases, so my guess would be a lot of these warnings are being driven by small-scale interactions with the hilly/mountainous terrain that is causing some elevated low-level rotation, but never enough to actually form a proper meso and tornado.
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No, terrain has nothing to do with it.

LLJ is extremely weak right now, and PBL wind vectors are a bit directional to the LLJ, which limits ESRH.

Vertical Instability is more than adequate right now, but until the LLJ strengthens, which won’t be until 7pm, this behavior will continue. Doesn’t mean a significant tornado can’t happen until then though.
 
Clancy said:
Despite the supercells, SRH is still meager in the lowest levels. This is expected to change, and I reckon we may see an uptick in tornadic activity in the coming hours.
View attachment 42757
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ColdFront said:
Fred just mentioned that as well. Low level shear will start vastly improving over the next few hours.
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Yep, nocturnal boost. I think the significant tornado threat drastically increases when the sun goes down, and as storms get into Alabama.

Oddly the HRRR doesn't show discrete convection ahead of the line anymore though
 
KM40 (Weather Station at Monroe County, MS Airport)
Temp: 88
Dew Point: 75
South wind at 10mph gusts to 17mph
 
UncleJuJu98 said:
Yep, nocturnal boost. I think the significant tornado threat drastically increases when the sun goes down, and as storms get into Alabama.

Oddly the HRRR doesn't show discrete convection ahead of the line anymore though
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At this point focusing on individual cam runs is pretty pointless.

There’s plenty of OWS supercells existing in reality, and they will continue to go on until the QLCS catches up with them.
 
jiharris0220 said:
No, terrain has nothing to do with it.

LLJ is extremely weak right now, and PBL wind vectors are a bit directional to the LLJ, which limits ESRH.

Vertical Instability is more than adequate right now, but until the LLJ strengthens, which won’t be until 7pm, this behavior will continue. Doesn’t mean a significant tornado can’t happen until then though.
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Not trying to be combative, but what model(s) are you basing this off of? Nothing I have seen shows the LLJ improving conditions, aside from a wind threat.

CAPE looks great across the area, but the lapse rates are poor (and expected to get worse per SPC Meso Analysis) so storms are struggling to take advantage of the CAPE.
 
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