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Severe Threat May 15-16, 2025

Ozonelayer said:
Sounding from northern Indiana on 03z Friday. Via the 00z NAM. No sure about you but...that analog.....Hate to see that on there.
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US_Highway15 said:
I was literally about to post this. I thought I was seeing things for a second, but that's literally the Moore 1999 tornado. Not gonna lie, I cannot recall a time (definitely recent in the past several years or even decade) where I've seen STP values this high for my hometown and neighboring areas. Definitely a daunting feeling I haven't experienced before.

Incredibly anxious to see IWX's morning AFD. Not to mention, I will be shocked if there's not an ENH D3 risk issued.
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Obligatory Mike Morgan post.

 
Depending on timing, the storms coming from the Northwest might actually mean the setting sun would help fuel their inflow.

The yellow ellipse is the sun's path over the US, and the dark orange cone is the direction of the sunset.

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Here is a 500mb and 250mb relative humidity. I'm using this to figure where cloud tops will most likely surface.

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Here's the average total cloud cover from the surface

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And here's the best representations of tornadic airflow I could find from Leigh Orf's supercomputer models of tornado genesis (his Youtube channel is an absolute gem).

The blue is cooler air, and the green/red is warmer air.



Here's another good one



And yet another because why not? This $hit is so awesome! This one actually shows different areas of vorticity represented as noodles.



As of now the models are showing explosions in convection starting late afternoon both Thursday and Friday, with a perfect amount of cloud clearing for solar energy to add fuel to the fire.
 
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Grand Poo Bah said:
Good gawd, this 00z GFS run is MEAN.

Looks like the Kinematics have backed off in TX, OK, and AR, but the set up is looking as potent as ever for the Midwest and Ohio Valley..

MO and TN are looking like the furthest south threat Friday.

Here's the Springfield and St Louis areas

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Next is the Knoxville, Nashville and Memphis areas. Check out the Memphis sounding analogs...

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Kentucky is also looking ugly. The tornado threat is so high even with strong caps partially due to the wet bulb temps (blue line) helping the surface air rapidly and easily saturate as it evaporates. The wet bulb temp will also act as a proxy for rapid cooling and condensation of air in the dry region and help strengthen updrafts and downdrafts, . It will essentially helps rising air reach free convection without excessive drying.
First sounding is the Bowling Green area... Look at that first analog again.... Second sounding is from the Louisville area.

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Here are soundings from Indiana and Illinois.... Once again, the worst analog possible keeps popping up...

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I'll be the first to say it (again lol). This has widespread tornado outbreak written all over it. An extremely potent one at that. I feel confident saying it, even after what happened on April 28th because the models are showing far more isolated convection than they ever did for April 28th. Even the GFS is showing it in ways I haven't seen all year. The dryline keeps getting sharper and sharper as well

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Those soundings…

Waking up to see how potent those soundings look was NOT what I expected this morning.
 
AJS said:
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Slight risk issued for Thursday.
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IMO this Day 3 outlook is as bizarrely conservative as the initial one issued for April 28 was bullish. The 500mb pattern for this upcoming event is a lot more textbook, which alone can make up for other deficiencies in the environment as seen on days like April 26, 2024 and March 5, 2022.
 
CheeselandSkies said:
IMO this Day 3 outlook is as bizarrely conservative as the initial one issued for April 28 was bullish. The 500mb pattern for this upcoming event is a lot more textbook, which alone can make up for other deficiencies in the environment as seen on days like April 26, 2024 and March 5, 2022.
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This is why it was maintained. Understandable in a way, but still conservative. You would think they would go the conditional route.

"15%/Slight risk probabilities were maintained for IN/western OH due to account
for low-probability, but potentially high-impact supercells within
this environment, but further refinements are likely as the
likelihood of convective initiation becomes more apparent."
 
Based off IWX's AFD, there is definitely uncertainty on the cap and if it were to break:

"Very warm on on Thursday as the 576dm ridge axis moves overhead. The
record high at Fort Wayne is 91 (2007, 1988) and 90 at South Bend
(1991). Forecast highs are in the upper-80s are increasingly
plausible as a mainly-dry day could be in the cards. The in-house
blend has really backed off on POPs (unsurprisingly) and this trend
continued today. An EML keeps things capped during the day, thus,
we`ll have plenty of instability for storms but no forcing mechanism
until a cold front arrives after sunset. CAMS will enter the
Thursday forecast domain later today which will help refine the
Thursday forecast. I anticipate the cap will hold until sunset at
which point storms ahead of the cold front drift in from Illinois.
The 500-mb jet overnight could prove a beneficial forcing mechanism
depending on its placement. All hazards are possible should the cap
be broken."
 
US_Highway15 said:
This is why it was maintained. Understandable in a way, but still conservative. You would think they would go the conditional route.

"15%/Slight risk probabilities were maintained for IN/western OH due to account
for low-probability, but potentially high-impact supercells within
this environment, but further refinements are likely as the
likelihood of convective initiation becomes more apparent."
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I was referring more specifically to the Wisconsin portion of the slight risk area, which would seem to be quite favorably positioned relative to the surface and upper-air features for a supercell tornado threat (similar to the way southeast Iowa was on March 31, 2023).

There are still some potential uncertainties primarily related to timing and capping, but I would have thought at least a 30% all-hazards hatched area (Enh risk) would have been warranted. Basically a compromise between what they did and the CSU output.
 
CheeselandSkies said:
I was referring more specifically to the Wisconsin portion of the slight risk area, which would seem to be quite favorably positioned relative to the surface and upper-air features for a supercell tornado threat (similar to the way southeast Iowa was on March 31, 2023).

There are still some potential uncertainties primarily related to timing and capping, but I would have thought at least a 30% all-hazards hatched area (Enh risk) would have been warranted. Basically a compromise between what they did and the CSU output.
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Ohhh, yeah that makes sense.
 
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