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6/19-6/23 Severe Weather Risk


Jim Martin

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off the 4km NAM at 0z between Dixon and Rochelle about

 

attachicon.gif4km nam weds.png

As is typical of the 4km, dewpoints being overdone.. But even then you're only lowering MLCAPE to 3000-3500 with LCL heights probably remaining around 800 meters or so...

 

That said, seems like that is perhaps convectively contaminated/influenced (ie, not exactly characteristic of the actual environment/wind profile.

nam4km_2016062112_036_40.28--87.64.png

 

This is further removed from the convective cluster... But even this has ridiculous shear profiles. A little northwest of here along the warm front, you get similar profiles to what you posted, far enough removed from convection that I wouldn't expect contamination. The shear profiles are pretty ridiculous and I would still expect something like 15% hatched tornado probs with a potential high risk for wind. Anything that remains discrete, semi-discrete, or RM embedded in lines...will have potential to be tornadic.

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I still don't know what the heck I'm going to get out of this.  Global models have storms firing late evening over central Iowa.  However, mesoscale models are largely bypassing the "slight" severe area and instead not firing storms until after midnight over far northeast Iowa.  I may not get much of anything if the latter scenario pans out.  Is this just a case of the mesos seeing a strong cap that the globals aren't?

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If we see enough of a break in the afternoon to allow the warm front to jump that far north, we're in real trouble

For sure... that's scary. The density of population here combined with tornadic cells would be beyond disaster. At this point, I would 100% AT LEAST keep the moderate risk into all of the LOT CWA as the whole area is under the gun and the wf could end up anywhere. It's simply too dangerous.

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Could have something to do with what I posted above. Also, I'm not sure how much input LOT has in this outlook but if they do, still being a day out and for consistency they might not want to have only one or two of their counties removed.

Our neighbors to the north and northeast gave input and SPC responded so there was really no need for us to also chime in once they said they weren't making any changes for MKX. If I would've given output, I may have recommended far northeast CWA and southeast WI to be pulled from the MDT.
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For sure... that's scary. The density of population here combined with tornadic cells would be beyond disaster. At this point, I would 100% AT LEAST keep the moderate risk into all of the LOT CWA as the whole area is under the gun and the wf could end up anywhere. It's simply too dangerous.

It might literally be May 3rd 99 in Illinois. Dangerous as dangerous can be.

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WGNs RPM still had the early round of storms sticking around the area at 2pm central and the second round firing just east and south of the city along I57 around 9pm and quickly moving into NWI where they really get going.  

 

At least from this 12pm forecast round 2 didn't seem like anything at all for the Chicagoland area.

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That cell on the NMM-WRF is well removed from surface-based instability. Hail, yes. Tornado, nassomuch.

 

What we'll have to watch is the timing of the vort/MCV that emanates in the Dakotas tonight (that I think will produce a serial derecho in the morning from IA to the Ohio Valley). There is enough disagreement on this timing that there could be room for rapid destabilization farther north towards the WI border, although the majority show too much festering convection along the baroclinic zone, keeping the warm front farther south. The earlier that vort comes through, the more likely Chicago will be under the gun. 

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Our neighbors to the north and northeast gave input and SPC responded so there was really no need for us to also chime in once they said they weren't making any changes for MKX. If I would've given output, I may have recommended far northeast CWA and southeast WI to be pulled from the MDT.

 

I see winds are forecasted to turn onshore, so I would think this far north shore area wouldn't be as "ripe" for the strongest storms.

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I still don't know what the heck I'm going to get out of this.  Global models have storms firing late evening over central Iowa.  However, mesoscale models are largely bypassing the "slight" severe area and instead not firing storms until after midnight over far northeast Iowa.  I may not get much of anything if the latter scenario pans out.  Is this just a case of the mesos seeing a strong cap that the globals aren't?

 

 

you're going to get trained tonight either way

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Forecast soundings and hodographs for wherever the WF is tomorrow on any given model are just insane. Pure weather porn. It is not just at 00Z either, as early as 18-21Z we see an environment that is very conducive to all modes of SVR wx. Given the current progged wind fields along w/ instability, anything that is discrete is likely going to be an absolute beast of a storm. With the cap that is expected to be in place, I see no reason not to expect a few discrete supercells for, at the very least, a couple hours before bowing out.

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Ok I know I'm not an SPC forecaster but I'm not sure where they are seeing strong unidirectional wind profiles. From what I seen the directional shear is pretty impressive. Obviously near the warm front is better for tornadic potential early on. I think with stronger capping to, that least the southern portion of a bowing mcs could be semi discrete. Just my personal opinion

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That cell on the NMM-WRF is well removed from surface-based instability. Hail, yes. Tornado, nassomuch.

 

What we'll have to watch is the timing of the vort/MCV that emanates in the Dakotas tonight (that I think will produce a serial derecho in the morning from IA to the Ohio Valley). There is enough disagreement on this timing that there could be room for rapid destabilization farther north towards the WI border, although the majority show too much festering convection along the baroclinic zone, keeping the warm front farther south. The earlier that vort comes through, the more likely Chicago will be under the gun. 

 

hrrr_ref_frzn_us_15.png

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It might literally be May 3rd 99 in Illinois. Dangerous as dangerous can be.

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This is why I don't even bother reading amwx any more. Bunch of fear mongering crap posts like this! Illinois has seen many tornado outbreaks and tomorrow is very unlikely to compare to them (unless if we get a violent tornado in an urban area).

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Here's a loop of 12z NAM 850-500 mb crossovers.  The 42 hour map appears to have malfunctioned so I left it out.  At least with these levels, you can see less crossover with time but it's not until very late and possibly behind the storms.

 

 

post-14-0-48417100-1466532142_thumb.gif

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Here's a loop of 12z NAM 850-500 mb crossovers.  The 42 hour map appears to have malfunctioned so I left it out.  At least with these levels, you can see less crossover with time but it's not until very late and possibly behind the storms.

 

 

attachicon.gifnam.gif

 

I wouldn't be surprised at all to see a mostly discrete to semi discrete storm mode across much of IL before it turns into a big wind event.

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This is why I don't even bother reading amwx any more. Bunch of fear mongering crap posts like this! Illinois has seen many tornado outbreaks and tomorrow is very unlikely to compare to them (unless if we get a violent tornado in an urban area).

Who are you again?
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