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June 28-July 1 Severe Threat


Thundersnow12

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But do we see a discrete storm this far east? Might be the saving grace where the best tornado threat stays west of Chicago metro.

My bet is that discrete supercells stay over in NE IA/S WI and maybe part of NW IL but I'd imagine that regardless of that there will be a considerable embedded TOR threat well into the evening. Even if it's not rush hour, 6-7PM is still not good timing for a major city

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..UPPER PORTIONS OF THE MID MS VALLEY AND UPPER MIDWEST  
 
A FAIRLY STRONG SIGNAL IS EVIDENT IN THE LATEST OUTPUT OF THE NCEP  
SREF...IN ADDITION TO THE DETERMINISTIC MODELS...SUGGESTING THE  
POSSIBILITY FOR THE EVOLUTION OF A RATHER SUBSTANTIAL ORGANIZED  
MESOSCALE CONVECTIVE SYSTEM DURING THIS PERIOD. THIS THREAT  
GENERALLY APPEARS FOCUSED EAST OF THE MIDDLE MISSOURI VALLEY INTO  
SOUTHWESTERN PORTIONS OF THE GREAT LAKES REGION MONDAY INTO MONDAY  
EVENING...WITH HIGHEST PROBABILITIES CURRENTLY APPEARING TO EXIST  
ACROSS SOUTHERN/EASTERN IOWA THROUGH NORTHERN ILLINOIS.  
 
GIVEN THE THERMODYNAMIC PROFILES WHICH APPEAR POSSIBLE...DOWNSTREAM  
OF THE BASE OF THE UPSTREAM UPPER TROUGH PIVOTING TOWARD THE  
REGION...THIS SCENARIO APPEARS REASONABLE...PARTICULARLY GIVEN THE  
STRENGTH OF THE ASSOCIATED WIND FIELDS AND SHEAR. THE ENVIRONMENT  
APPEARS CONDUCIVE TO DEVELOPMENT OF CONVECTION CAPABLE OF PRODUCING  
LARGE HAIL AND ONE OR MORE LENGTHY SWATHS OF DAMAGING WINDS.  
SUPERCELLS WITH TORNADOES MAY ALSO NOT BE OUT OF THE QUESTION.  
HOWEVER...MUCH WILL DEPEND ON THE CONVECTIVE EVOLUTION ACROSS THE  
NORTH CENTRAL PLAINS AND MID MISSOURI VALLEY LATER TODAY AND  
TONIGHT...AND ITS IMPACT ON THE ENVIRONMENT FARTHER EAST. THIS  
REMAINS THE PRIMARY SOURCE OF UNCERTAINTY FOR THE CONVECTIVE  
POTENTIAL FOR MONDAY...WHICH COULD BE MORE SUBSTANTIAL THAN  
CURRENTLY DEPICTED IN THE CATEGORICAL AND PROBABILISTIC FORECASTS.  

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My guess is we will be seeing a 30% hatched area appear first, then a MDT Risk at 1730z (similar to what happened in yesterday's day2 ). Although, has a 15% SLGT Risk ever gone straight to MDT? Don't recall something like that happening recently at the moment.

Seems that the general idea is this 15% Slight risk is too conservative, and we ought to be at a higher-end Slight risk. Though yes, it would be quite a feat to go from basic Slight to MDT. In this case, though, I think we're already somewhere in a higher end Slight risk, should the current D3 outlook be too conservative.

Edit: And looks like that's the case.

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Seems that the general idea is this 15% Slight risk is too conservative, and we ought to be at a higher-end Slight risk. Though yes, it would be quite a feat to go from basic Slight to MDT. In this case, though, I think we're already somewhere in a higher end Slight risk, should the current D3 outlook be too conservative.

Edit: And looks like that's the case.

Yep, there it is.

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00z Euro appears to be somewhere in between the GFS and NAM threat level wise, which is definitely concerning considering the NAM is still a pretty high end setup. It certainly has supercells going in E IA at 21z, with 4000+ J/kg CAPE to feed on.

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Mother of all things holy at the 06z GFS soundings...NW IL at 21z.  :twister:

 

0BF1qaD.gif

 

In other news, we have a supercell tornado warned in KS at quarter after 5 in the morning right now, that's a rather ominous sign.

 

There is really no mention of tornadoes at all in any of the morning AFDs aside from a passing mention from ILX.

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Some of the higher res models from 00z last night and also the 4km NAM this morning want to pop convection out in central Iowa around noon/early afternoon tomorrow.  This then quickly evolves into a complex that blasts east towards the IA/IL border towards 00z.  With the intense LLJ blasting into Iowa tomorrow morning storms kicking off that early doesn't seem too unreasonable.  If it quickly evolves into a mature complex then we may see less of a tor threat for areas further to the east, but with so much shear there's a good chance we could see embedded sups along the line which could tor quite easily.  Definitely gonna be some very high wind reports evolving out of something like this as well, especially early tomorrow evening further to the east when the cold pool really gets things going.  Probably see one hell of a rear inflow jet associated with part of the complex as well.  Any cells that can pop ahead of the line/complex could easily drop a tornado as well, so this is gonna be a very interesting/dangerous event to be sure. 

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Yeah the one "if" is do we see more pre frontal convection say near the IA/IL border. Then all bets are off and you'll have sig tor potential.

Another thing, what will win out? Decent venting down shear due to the strong mid level jet to maybe give a more classic sup look of will such high PWATS cause HP rather quickly

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Yeah the one "if" is do we see more pre frontal convection say near the IA/IL border. Then all bets are off and you'll have sig tor potential.

Another thing, what will win out? Decent venting down shear due to the strong mid level jet to maybe give a more classic sup look of will such high PWATS cause HP rather quickly

If we have the upper-level flow that the NAM is progging, the venting will likely win out.

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No denying it, tomorrow could be pretty bad if potential is fully realized.  I'm really concerned about eastern Iowa, northern Illinois, southern Wisconsin.  Other than Parkersburg in 2008 (which is more like central Iowa), there hasn't been a violent tornado anywhere in that region since 1990 and tomorrow is probably as good a shot as any setup in recent years.  The last time I posted about somebody's violent tornado drought was on March 1, 2012 in regards to Indiana and we know what happened the next day.  I hope it doesn't pan out this time.    

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given the initiation point trends and overwhelming model tendency to congeal things into a semi-linear complex, i'll be surprised if we see a single TOR in LOT's CWA

 

Are you tempting fate like you did with the no hail over 1" call a few weeks back?

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