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July 11-14 Severe Weather Event


Powerball

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Seems SPC will go high risk if there's enough clearing. Tornado outbreak not out of mind either. They'll probably go high risk with a 60% for wind/hail and a 15% risk for tornadoes unless the cells are a lot more discrete in central IL. But my tornado area would be Central IL with very high instability and efficient shear and a 80 Knot mid-layer flow. 

 

 

I don't know.  I think it would be more likely that any high risk comes on the 13z or 1630z outlook, once the effects of the morning MCS are more clear.  But certainly if any mets here have inside info on the 6z outlook, feel free to share.  :guitar:

 

Edit:  I missed some key words in your post the first time, which would suggest you weren't implying a 6z high risk.  Never mind I guess. 

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DVN and ILX 00z soundings were uncapped 4k j/kg of CAPE and WAA wing already lighting up with convection from central IL to SW WI. Getting concerned we're gonna have hydro issues tonight, which as others has mentioned could be a problem with any high end damaging winds.

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DVN and ILX 00z soundings were uncapped 4k j/kg of CAPE and WAA wing already lighting up with convection from central IL to SW WI. Getting concerned we're gonna have hydro issues tonight, which as others has mentioned could be a problem with any high end damaging winds.

HRRR has been showing some really nasty training in some areas that already have active flood warnings. Could see some flash flood emergencies if that's the case

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DVN and ILX 00z soundings were uncapped 4k j/kg of CAPE and WAA wing already lighting up with convection from central IL to SW WI. Getting concerned we're gonna have hydro issues tonight, which as others has mentioned could be a problem with any high end damaging winds.

 

Probably doesn't matter if it rains a drop tonight/early overnight...down here in your southern CWA. Ground is already completely saturated. As such, hoping for the best here locally with whatever rolls through tomorrow morning and evening (damaging wind wise)...but preparing for the worst.  

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Probably doesn't matter if it rains a drop tonight/early overnight...down here in your southern CWA. Ground is already completely saturated. As such, hoping for the best here locally with whatever rolls through tomorrow morning and evening (damaging wind wise)...but preparing for the worst.

It could affect the Northern Areas tho. We aren't as saturated as the southern portions of Chicago.
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DVN and ILX 00z soundings were uncapped 4k j/kg of CAPE and WAA wing already lighting up with convection from central IL to SW WI. Getting concerned we're gonna have hydro issues tonight, which as others has mentioned could be a problem with any high end damaging winds.

 

 

Watching the NMM and ARW as they come in, and both dump good (bad) amounts in parts of northeast IL/northwest IN.

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DVN and ILX 00z soundings were uncapped 4k j/kg of CAPE and WAA wing already lighting up with convection from central IL to SW WI. Getting concerned we're gonna have hydro issues tonight, which as others has mentioned could be a problem with any high end damaging winds.

 

There were some pretty decent towers building overhead shortly after sunset in this area.  Was wondering if they may take off at some point as they moved off out of the area.  

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Just a few thoughts/predictions based off of model trends and subjective analysis with respect to overnight/morning convection...

 

The models were virtually all wrong with the southward extent of convection tonight. Models, generally, blew up storms over far southern MN into IA, but there's been pretty much nothing there. There's one cell over SD, but even the HRRR shows that fizzling. Some speculated that this cell would blow up into an MCS over IA. I don't see that happening.

 

With this said, although some convection may eventually fire over portions of IA, I think the main player is the MCS over MN/WI. On the current trajectory, that should affect much of central/southern WI and probably northern Illinois. The result is little to no air-mass disruption south and west of US-52, which would support extreme instability across eastern IA and central/NW IL by afternoon. I think Chicagoland may have some convective debris to somewhat limit destabilization. The morning convection should leave an outflow boundary somewhere southwest of Chicago, perhaps close to US-52? The HRRR/NAM seem to favor a boundary/wind-shift across far eastern IA into central IL.

 

The next question comes to the timing of afternoon initiation. Latest HRRR runs show initiation across south-central to SE IA by 16-17z, but I'm a bit skeptical. I suppose this is possible. That could lead to a mixed and messy evolution, depending on how quickly storms can become surface-based and if any storms can latch onto a front/boundary. 

 

Assuming that overnight/morning convection is limited (SW of US-52) AND initiation is held off until mid to late afternoon, that's going to lead to an ugly scenario with extreme instability coinciding with strong shear. I am not 100% sold on this, as rarely does a setup (especially this year) take full advantage. As we've seen with some progs (and thinking back to previous events in the IL vicinity this year), even ongoing convection in the morning won't completely rule out this event, as I think we're at a point of no return where there will be intense storms tomorrow. I doubt anything will change that at this juncture, given trends and obs.

 

Final thoughts:

I would tend to favor a solution where some spotty shower activity or weak convection manages to get going in the morning across E IA/central IL, but does not have much of an effect on destablization. It's probable that some rogue storms fire early in the afternoon and pose somewhat of a severe risk, but the better chance of severe, some significant, should be from mid/late afternoon into the evening hours. I think we're looking at a corridor slightly west of the previous SPC outlook, targeting E IA into much of central into NW IL, but primarily SW of US-52. You can't write off a threat in Chicagoland with this sort of setup (small margin of error could have major implications on a large population), although I think the strongest storms stay southwest of the city.

 

Edit: To clarify geographical region in the final paragraph - changed "northern half of IL" to "central/NW IL."

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00z NMM and HRW really don't have anything in IL until around/after 00z Tuesday (moving in from WI). Long lull between the morning stuff and the evening activity.

ARW east does look like you can infer initiation occurred somewhere between 21-00z because it has discrete activity on top of northern IL at 00z in sim ref.

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Just a few thoughts/predictions based off of model trends and subjective analysis with respect to overnight/morning convection...

The models were virtually all wrong with the southward extent of convection tonight. Models, generally, blew up storms over far southern MN into IA, but there's been pretty much nothing there. There's one cell over SD, but even the HRRR shows that fizzling. Some speculated that this cell would blow up into an MCS over IA. I don't see that happening.

With this said, although some convection may eventually fire over portions of IA, I think the main player is the MCS over MN/WI. On the current trajectory, that should affect much of central/southern WI and probably northern Illinois. The result is little to no air-mass disruption south and west of US-52, which would support extreme instability across eastern IA and central/NW IL by afternoon. I think Chicagoland may have some convective debris to somewhat limit destabilization. The morning convection should leave an outflow boundary somewhere southwest of Chicago, perhaps close to US-52? The HRRR/NAM seem to favor a boundary/wind-shift across far eastern IA into central IL.

The next question comes to the timing of afternoon initiation. Latest HRRR runs show initiation across south-central to SE IA by 16-17z, but I'm a bit skeptical. I suppose this is possible. That could lead to a mixed and messy evolution, depending on how quickly storms can become surface-based and if any storms can latch onto a front/boundary.

Assuming that overnight/morning convection is limited (SW of US-52) AND initiation is held off until mid to late afternoon, that's going to lead to an ugly scenario with extreme instability coinciding with strong shear. I am not 100% sold on this, as rarely does a setup (especially this year) take full advantage. As we've seen with some progs (and thinking back to previous events in the IL vicinity this year), even ongoing convection in the morning won't completely rule out this event, as I think we're at a point of no return where there will be intense storms tomorrow. I doubt anything will change that at this juncture, given trends and obs.

Final thoughts:

I would tend to favor a solution where some spotty shower activity or weak convection manages to get going in the morning across E IA/central IL, but does not have much of an effect on destablization. It's probable that some rogue storms fire early in the afternoon and pose somewhat of a severe risk, but the better chance of severe, some significant, should be from mid/late afternoon into the evening hours. I think we're looking at a corridor slightly west of the previous SPC outlook, targeting E IA into much of central into NW IL, but primarily SW of US-52. You can't write off a threat in Chicagoland with this sort of setup (small margin of error could have major implications on a large population), although I think the strongest storms stay southwest of the city.

Edit: To clarify geographical region in the final paragraph - changed "northern half of IL" to "central/NW IL."

As always excellent write up, Quincy would have to agree with all of your points. Are you chasing tomorrow?

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Turning out to be a pretty tough forecast for tomorrow.  Seeing quite a bit of disagreement among the CAMs tonight.  As per usual, it's really going to come down to how tonight and tomorrow morning's convection evolves.  Of course we have the main MCS in western WI/eastern MN right now, but we also see some additional storm development in other areas.  Instead of just a progressive linear MCS we also have backbuilding convection behind it from St. Cloud back to Fergus Falls.  We also have convection festering in both North and South Dakota.  These additional areas could flare out, but they could also organize, and grow upscale into a progressive MCS or two that could have a large impact downstream.  None of the current models seem to have a handle on this convection.  If these other areas indeed end up growing into something more meaningful, they could have an impact on tomorrow, as they will arrive into tomorrow's risk area much later than the original MCS.  Of course this wouldn't be a deal breaker for tomorrow's setup, but it could impact on where future development takes place, etc.  

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As always excellent write up, Quincy would have to agree with all of your points. Are you chasing tomorrow?

I will be out, it's looking like the last chase of my season, unless I get desperate and go into the TN Valley on Tuesday.

 

Still can't help but think something odd is going to happen this morning into early afternoon. Is it random convection blowing up? Storms firing by midday? A boundary shifting further SW (or even NE) than forecast? I'd be willing to bet some odd wrench gets thrown into the mix, but I doubt that kills the overall threat. If anything, it could mean some early day severe and/or locally enhanced shear leading to an elevated tornado threat somewhere.

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I will be out, it's looking like the last chase of my season, unless I get desperate and go into the TN Valley on Tuesday.

 

Still can't help but think something odd is going to happen this morning into early afternoon. Is it random convection blowing up? Storms firing by midday? A boundary shifting further SW (or even NE) than forecast? I'd be willing to bet some odd wrench gets thrown into the mix, but I doubt that kills the overall threat. If anything, it could mean some early day severe and/or locally enhanced shear leading to an elevated tornado threat somewhere.

 

Kinda how it goes with these events in the MW, especially in the summer lol.  You do all these forecasts for days, but many times you wake up and basically see what you have to work with. 

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While the outlook didn't mention a potential upgrade to high risk, this line struck me

 


AND A  CONSIDERABLE DAMAGING WIND RISK WITH THE POTENTIAL FOR ONE OR MORE  DERECHO-PRODUCING MCS/S ACROSS THE REGION TODAY AND TONIGHT.

 

 

17 million in the moderate risk area.

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