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July 11-14 Severe Weather Event


Powerball

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Very distinct discrete supercell tracks on the 12z 12km NAM qpf fields tomorrow evening. And very scary tracks at that. Chicago metro and QCA.

00z

03z

 

The low levels really take off after 21z tomorrow.  Surface all the way up to 850 the winds really respond and stay relatively backed.  Pretty scary scenario given the instability potential, and that seasonally strong upper jet right overhead.

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GFS and NAM still look great for tomorrow. 

 

ILN's morning AFD:

 

.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/...
WILL LIKELY SEE SOME SCATTERED THUNDERSTORMS LINGERING INTO THIS
EVENING...ESPECIALLY ACROSS OUR SOUTHWEST...AND AGAIN ASSUMING WE
ARE ABLE TO DESTABILIZE ENOUGH THROUGH THIS AFTERNOON. WE COULD
THEN GET INTO A LULL OVERNIGHT AS A POSSIBLE MCS ACROSS THE
WESTERN GREAT LAKES SHOULD REMAIN TO OUR NORTHWEST THROUGH THE
NIGHT. THE REMNANTS OF THAT MCS COULD WORK DOWN INTO OUR AREA
THROUGH MONDAY MORNING AND THE NORTHWARD EXTEND OF THE
AFOREMENTIONED BOUNDARY WILL AGAIN BE DEPENDENT ON HOW THAT MCS
PLAYS OUT. MODELS ARE IN GOOD AGREEMENT THOUGH DEVELOPING STRONG
INSTABILITY ALONG AND TO THE SOUTHWEST OF THIS BOUNDARY...UP INTO
OUR AREA THROUGH THE AFTERNOON ON MONDAY. WITH VERY IMPRESSIVE
SHEAR VALUES/HELICITIES...ALL SEVERE WEATHER MODES WILL BE
POSSIBLE MONDAY AFTERNOON INTO MONDAY NIGHT.
HEAVY RAIN WILL ALSO
BE LIKELY. RIGHT NOW THE AXIS OF BEST ACTIVITY LOOKS LIKE IT WOULD
RUN ACROSS AT LEAST THE SOUTHWEST HALF OF OUR
FA SO WILL LIKELY
EVENTUALLY NEED AN FFA OUT FOR AT LEAST THOSE AREAS. WITH THAT
STILL BEING A WAYS OUT THOUGH WILL CONTINUE TO HANDLE THAT THREAT
IN THE HWO. THE THREAT FOR THUNDERSTORMS WILL THEN CONTINUE INTO
TUESDAY AS THE MID LEVEL TROUGH AXIS PIVOTS DOWN ACROSS OUR AREA.

 

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Assuming the morning MCS doesn't foul things up, northern IL is in big trouble tomorrow.  Not only all severe hazards possible, but high-end severe hazards.  Will be interesting to see how long discrete mode can be maintained.

I don't even think maintained would matter much for Chicago especially if the afternoon development forms right over them. It will be supercells initially and if they develop over the metro area things are going to get ugly fast. The amount of instability is incredibly high and it seems every run as we get closer to tomorrow is inching the shear profile upward. Not to mention you really don't need great bulk shear when you have 5000 J/kg SBCAPE. The fact that we might end up having the good shear collocated with extreme instability really puts a high end risk for the area. It will be very interesting to track tomorrow.

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you know south is the way to go

 

You are usually spot on with your trend calls and so far SPC has agreed with you. However, models have been spuriously depicting strong activity over Chicagoland, including the 4km NAM, as Ricky posted above. It would seem to make sense, being that it would be following the instability gradient. I'm curious to see if SPC bumps the moderate a little northeast on their Day 2 update.

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You are usually spot on with your trend calls and so far SPC has agreed with you. However, models have been spuriously depicting strong activity over Chicagoland, including the 4km NAM, as Ricky posted above. It would seem to make sense, being that it would be following the instability gradient. I'm curious to see if SPC bumps the moderate a little northeast on their Day 2 update.

 

Easy call.

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I'm not as good at this as most, these threats are primarily wind gusts from derechos with a relatively low chance of TORs?

 

Tomorrow isn't really that case. It probably won't be a large scale tornado outbreak per say, but the threat is higher than with just a purely derecho/MCS event, depending on storm mode.

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Tomorrow isn't really that case. It probably won't be a large scale tornado outbreak per say, but the threat is higher than with just a purely derecho/MCS event, depending on storm mode.

 

 

Agreed.  I think IF we get a high risk tomorrow, it's more likely to be for wind than tornadoes, but tomorrow is one of those days that is capable of tornadoes with potential for a high end one or two, and that threat would only be heightened with local backing of the surface winds or favorable storm scale interactions.  Not a coincidence imo that 7/13/04 and 8/28/90 are showing up on those SHARPy soundings.

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I heard from someone whos uncle works for the NWS (I've confirmed his uncle is an employee, he aint bluffing) that the SPC is considering a day one High Risk for Wind across Illinois and Exteme Nortwest Indiana.

That's a strange place to put the high risk... you'd think the 60% wind would be placed where the bow echo is most mature

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^Wouldn't surprise me.  After this thing gets organized into a mature MCS with a strong cold pool later tomorrow evening it's going to do some serious work as it heads southeast.  Much of Indiana looks like it has the best shot for some of the higher wind potential later tomorrow evening as far as coverage.  Large cape, impressive LLJ, loaded downdrafts, rear inflow momentum transfer with the strong mid-upper jet right overhead, etc.  Could end up being a textbook derecho if things go as they look now.  Gonna be one hell of a lightning show as well lol.

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