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Severe Threat May 15-16, 2025

US_Highway15 said:
That means it won't then (I'm only half kidding).
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As of right now Norman, OK NWS is mentioning all hazards


1747244101671.png






From FWD (DFW)



Convection is likely to be a little more widespread on Saturday as
an embedded shortwave ejects out of the Desert Southwest and into
the Southern Plains. With the dryline expected to make a push a
little farther eastward, modest forcing for ascent and strong
afternoon heating should weaken the cap sufficiently for scattered
severe thunderstorms to develop. Uniformly weak low level wind
fields and relatively high LCLs suggest a low tornado threat, but
strong deep layer shear, steep lapse rates, and strong instability
indicate the potential for large hail and a few instances of
damaging winds will be possible. Coverage of afternoon/evening
storms is expected to be 30-40%.

A similar setup is expected on Sunday although weaker synoptic
forcing may keep convection tied closer to the dryline itself and
generally north of I-20 through the late afternoon. A few severe
storms with large hail and damaging winds will be possible Sunday
afternoon and evening with PoPs 20-30%. Continued troughing to our
west into early next week will likely keep the dryline active with
periodic severe storms developing during peak heating and
continuing into the late evening hours. We`ll maintain PoPs each
afternoon through Tuesday to account for this activity.
 
Y'all see that cell near Lake Winnebago on 12z HRRR? Should that be of any concern? I'm still learning how to read hodographs & soundings, but someone told me that cell and the sounding in front of it is volatile.
 
12Z MPAS-HN (using MPAS core, NSSL microphysics and HRRR initial conditions) and MPAS-HT (MPAS core, Thompson microphysics and HRRR initial conditions) models show supercells initially developing all over the ENH risk area and then in IWX's region, developing into a bow-echo line, sweeping through Ohio). I could see one of these solutions verifying *IF* the cap breaks. Considering both these models use a portion of the HRRR, and are now showing the cap breaking, I'm anxious to see the 18Z HRRR run and see if it finally shows the same (cap breaking) over the ILX/IWX area.

MPAS-HN
floop-mpas_nssl_hn-2025051412.refcmp_uh001h.us_mw.gif
MPAS-HT
floop-mpas_nssl_ht-2025051412.refcmp_uh001h.us_mw.gif
 
Kds86z said:
View attachment 41474
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I think tonight's 18Z and 00Z runs showcasing whether the cap breaks or not will dictate whether that 10% hatched TOR risk gets pushed further down south into ILX/IWX. I think if it shows that, then they'll move it farther south thanks to the shear rates of 40-50 knots sweeping through the area. If it doesn't, I think those regions stay in the 5%.
 
CAMs seem split on the cap breaking. NAM is definitely more bullish on the cap breaking and verbatim would be a regional tornado outbreak. HRRR maintains a strong cap throughout the evening on Thursday.

Watching for trends in the models right now, particularly around CIN (capping inversion).
Overall, there seems to be a slight downward trend in CIN across the models, although some models are maintaining or slightly increasing CIN tomorrow afternoon.

Tough forecast, highly conditional. I think 30-40% odds of a regional tornado outbreak and 60-70% odds of not much at all.
 
US_Highway15 said:
12Z MPAS-HN (using MPAS core, NSSL microphysics and HRRR initial conditions) and MPAS-HT (MPAS core, Thompson microphysics and HRRR initial conditions) models show supercells initially developing all over the ENH risk area and then in IWX's region, developing into a bow-echo line, sweeping through Ohio). I could see one of these solutions verifying *IF* the cap breaks. Considering both these models use a portion of the HRRR, and are now showing the cap breaking, I'm anxious to see the 18Z HRRR run and see if it finally shows the same (cap breaking) over the ILX/IWX area.

MPAS-HN
-gif
MPAS-HT
-gif
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Both solutions do show quite a monster wind bag, potentially derechos through Ohio. That's the thing that is really catching my eye right now, although I'm biased because I'm an Ohio guy.

But from what I'm hearing now, it's a very Plains-like setup which is so weird for the upper midwest. I'm more on the side that there won't be much in terms of a tornado outbreak though - the trend of CIN building into the region is always one that makes me believe that initiation is gonna be tough for these storms.
 
Just realized how many people there are from Columbus on this forum, haha. Hopefully we just get some pretty clouds and green skies (although the former almost never happens), but usually we stay clear of tornadoes for some reason.
 
slenker said:
Here's a sounding I pulled from northern Indiana close to the Michigan border at 01z for the 18z HRRR. This is out ahead of a few cells that popped up too. Notice the 5/3/99 OKC analog that has continued to pop up for a while now:
View attachment 41485
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I don't live in Michigin but I live in western PA. I think I can speak for a lot of folks when I say we really just don't get environments up here quite often, even ignoring the plains-like nature of it. Its often rare, but when it happens you get events like Palm Sunday 1965 and 5/31/1985. Not to say this event will be even comparable to those two, but the same concern of whether or not the cap would break was there for the '85 event, and look what happened.

My point is that even if its a conditional risk, the ceiling may be MDT worthy. And because of this, everyone needs to be prepared for the worst in this area.
 
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