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Severe Threat May 15-16, 2025

slenker said:
April 2nd was a very surprising high risk upgrade to a lot of us, including me - I most certainly did not agree with it, but I stood corrected watching that day unfold. The reason they did it was because the SPC has access to a lot of things we do not and the tools they had pointed to a higher end solution than the regular CAM models like the HRRR and NAM were pointing to that day.

Whatever the SPC does is based on a lot more than what we have access to, for the most part.
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Quickly off-topic, but the Convective Chronicles video with Broyles does an amazing job breaking down why they went with the HIGH that day.

Anyways, yeah, I don't think they're going with a HIGH. MDT, maybe, but unless the SPC knows something we don't (which could very well be true) I don't know if they have enough confidence to go with it.
 
OH-IOan said:
Quickly off-topic, but the Convective Chronicles video with Broyles does an amazing job breaking down why they went with the HIGH that day.

Anyways, yeah, I don't think they're going with a HIGH. MDT, maybe, but unless the SPC knows something we don't (which could very well be true) I don't know if they have enough confidence to go with it.
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Yup! That’s where I got that info from. It’s cool that that high risk wouldn’t have been possible in years past and with the recent developments of OMEGA and whatnot, it allowed them to efficiently forecast a very sneaky day that ended up verifying well into the high risk range.

Don’t want to derail this thread though - I don’t think a high risk is in the cards either tbf.
 
Were the HRRR, RRFS or even to an extent NAM solutions to verify I think we could be looking at a High Risk caliber forecast.

There is obviously a LOT more that goes into the forecast than that, and trying to 'predict' what itself is a prediction is bit futile especially at this range. This is also not me saying I necessarily think one is going to happen.

But were one to be issued, I would not be surprised in the slightest.
 
UK_EF4 said:
Were the HRRR, RRFS or even to an extent NAM solutions to verify I think we could be looking at a High Risk caliber forecast.

There is obviously a LOT more that goes into the forecast than that, and trying to 'predict' what itself is a prediction is bit futile especially at this range. This is also not me saying I necessarily think one is going to happen.

But were one to be issued, I would not be surprised in the slightest.
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Yeah I agree. Especially if the day 2 moderate is issues this afternoon.
 
A D2 MDT would show that the SPC is indeed confident in the threat, and I'd change my mind if that is issued. "Uncertainty" is the make-or-break for a HIGH here, and only a MDT would show that they are indeed aware of how dangerous the setup is.
 
What would take this event to the next level for me, is if substantial convection is shown firing in north Mississippi and North Alabama. That would make the scope of this event even bigger imo. Not out of the realm of possibility.
 
The HRRR and NAM are now both consistently showing intense helicity tracks over Chicago / central Cook County today. Indicative of several supercells riding the boundary.

NAM has been consistent with this for the past 4 runs. HRRR has been showing this on a few runs but the signal is getting more consistent.

Other than parks, Cook County is 100% developed, highly populated land, if any tornado that drops it will cause substantial damage.
 

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06z guidance is all over the place with regard to the threat in my backyard Friday. HRRR depicts two consecutive rounds of storms up this way but neither have a ton to work with, which would temper the northern extent. On the other hand, both the NAM and the NAM 3k keep convection at a minimum along the Ohio River until after 0z Saturday, allowing a favorable environment for severe thunderstorms to take place in advance of an MCS. There would be an appreciable risk for QLCS tornadoes along the ohio river in this scenario.

Interested to see what the 12z suite suggests.
 
lake.effect said:
The HRRR and NAM are now both consistently showing intense helicity tracks over Chicago / central Cook County today. Indicative of several supercells riding the boundary.

NAM has been consistent with this for the past 4 runs. HRRR has been showing this on a few runs but the signal is getting more consistent.

Other than parks, Cook County is 100% developed, highly populated land, if any tornado that drops it will cause substantial damage.
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The 2021 Naperville EF3 is a great example of that. Besides a field at the very start of its path and a few golf courses here and there, that thing trekked right through residential areas throughout its entire path. It's a miracle nobody died.
 
UncleJuJu98 said:
What would take this event to the next level for me, is if substantial convection is shown firing in north Mississippi and North Alabama. That would make the scope of this event even bigger imo. Not out of the realm of possibility.
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MCS looks to be in the cards for sure. Not sure about discrete activity with the cap in place, but it wouldn't be impossible.
 
Brice W said:
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Yeah seems very well forecasted so far. Nothing that sticks out too much in disagreement honestly. Could maybe see a small moderate around southern Illinois pushing into a small portion of western Kentucky.
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The helicity streak going through southern MO/IL/IN looks eerily reminiscent of the 1925 Tri-State Tornado's path through that general area. Let's hope that a repeat performance is not what ends up happening!
 
OH-IOan said:
The 2021 Naperville EF3 is a great example of that. Besides a field at the very start of its path and a few golf courses here and there, that thing trekked right through residential areas throughout its entire path. It's a miracle nobody died.
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Right! And that's not even Cook county.

Chicagoland covers 13 counties, and of those Cook, Lake, Dupage are almost 100% developed, high population density counties. It's not good to see a concentrated risk over that area.
 
At this point, LOT (NWS Chicago) region definitely has a higher-end tornado threat, than the IWX region. I think similar to what the METs at IWX said, the LCL numbers being above 1000m will keep the tornado threat from becoming elevated over here, unless anything changes. I do wonder if we get caked in sunshine all throughout the day if that will change anything tornado threat wise. I doubt it though.
 
UncleJuJu98 said:
12z hrrr takes a significant deviation from the 06z. Looks like mainly a damaging wind event. I'll toss that one for now lol. See what the next one says
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Yeah the 12z is definetly an outlier. Goes from tornado outbreak to possible derecho. My bet is something in between, specifically supercells at first that later form into a squall line somewhere in east central KY/TN.
 
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