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July 15-20 Severe Weather


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Props to the nws offices and spc keeping pops low despite aggresive models and impressive parameters.

Maybe the llj does the trick overnight

Well that is the main problem, there really is no LLJ. Nocturnal LLJ's are typically a feature of the plains owing to differential cooling due to sloping terrain and the development of a geostrophic wind which is then turned via the coriolis. Of course dynamic LLJ's can develop anywhere, but under this ridge pattern there are no dynamical forces on the synoptic scale to force a LLJ here. As you mentioned earlier, this setup was much more reliant on cold pool generation and propagation to initiate new cells. Convective allowing models like the HRRR struggle big time with these weakly forced situations but with the presence of extreme instability. It is similar to what Hi-res models like the HWRF do in the tropics.

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I would have bet money that the storms up in central Wisconsin were gonna rake southern Wisconsin and northeast Illinois this evening. They were fairly well organized early in the evening, but fell just short of organizing enough to start the forward propagation process. There really wasn't a shortwave mixed in the NW flow, but mid level winds certainly weren't nothing to sneeze at. I still wouldn't write off some storms quickly blowing up later tonight with all the lingering boundaries from earlier today and this evening's convection.

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In regards to the Wednesday threat, I'm worried about too much convection firing too early. GFS and NAM have convection going very early in the warm sector.

Also, a quick frontal passage could lessen the threat for anything substantial here in S MB.

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Man you just gotta love these insane mid-summer, late evening parameters on the SPC meso page. The 10pm CDT analysis features 6000j/kg of mixed layer cape over northeast Iowa/southwest Wisconsin. That's freaking obscene. Effective sig tornado values of 7 near Chicago. Supercell composite of 28 over most of northeast Illinois. 1km EHI of 7 over northeast Illinois.

The above figures are the kind we can only dream of early on during the severe weather season, like in March when it's exciting to see a little bubble of 750j/kg of cape in the forecast lol.

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Man you just gotta love these insane mid-summer, late evening parameters on the SPC meso page. The 10pm CDT analysis features 6000j/kg of mixed layer cape over northeast Iowa/southwest Wisconsin. That's freaking obscene. Effective sig tornado values of 7 near Chicago. Supercell composite of 28 over most of northeast Illinois. 1km EHI of 7 over northeast Illinois.

The above figures are the kind we can only dream of early on during the severe weather season, like in March when it's exciting to see a little bubble of 750j/kg of cape in the forecast lol.

We were THIS close to having that storm is WI break the cap and put down a sig tor between I-39 and rt 47 in northern IL given it stayed discrete in that insane environment. We dodged a big bullet tonight.

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We were THIS close to having that storm is WI break the cap and put down a sig tor between I-39 and rt 47 in northern IL given it stayed discrete in that insane environment. We dodged a big bullet tonight.

Yeah there was probably a very fine line between what happened and what could have been. Given the tornadic potential over northeast Illinois it was probably a good thing.

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We were THIS close to having that storm is WI break the cap and put down a sig tor between I-39 and rt 47 in northern IL given it stayed discrete in that insane environment. We dodged a big bullet tonight.

Yeah, but with the way the cap this year has been destroying things this year, it was always somewhat doubtful.

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Yeah, but with the way the cap this year has been destroying things this year, it was always somewhat doubtful.

Big boom/bust this year, this makes me concerned that the late season into fall this year could end up being very exceptional especially with seasonally strong systems that come with the late summer/early fall time frame.

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Big boom/bust this year, this makes me concerned that the late season into fall this year could end up being very exceptional especially with seasonally strong systems that come with the late summer/early fall time frame.

Not good, especially with all that the south has been through this year. I wrote in the radar thread that I had a bad feeling like something big was just around the corner (and it wasn't related to the tropics).

Also, on a short term scale, I feel a potentially significant threat may exist tomorrow across Central Minnesota.

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Not good, especially with all that the south has been through this year. I wrote in the radar thread that I had a bad feeling like something big was just around the corner (and it wasn't related to the tropics).

I wouldn't be surprised if we had an active fall this year. EML/Drought areas aren't going anywhere soon, and within a month we will start transitioning into late summer type pattern with occasional shots of cooler Canadian air. Interesting times ahead.

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Do you think it will be colder than average in the north (Canada, etc.) this fall? That would spell major problems regarding stronger convergence between warm and cold air masses and likely a stronger jet stream and storm systems across the Midwest and South...

Considering the weather has been abnormally cold here in the Pacific NW (among other places), once that jet begins to dip back south, interesting things could begin happening.

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DSCN1114.JPGDSCN1145.JPGDSCN1133.JPGDSCN1122.JPG

From the LaMoure County high-end EF3 on July 17th. Very fortunate that his tornado did not go through a more populated area. It almost certainly would've been rated higher if more structures were in its path and could've easily been a killer tornado because it was heavily rain-wrapped. Berlin would've been absolutely hammered if this thing tracked slightly further east. Bowdle-like situation. The survey said at least a half-mile wide damage path.

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DSCN1114.JPGDSCN1145.JPGDSCN1133.JPGDSCN1122.JPG

From the LaMoure County high-end EF3 on July 17th. Very fortunate that his tornado did not go through a more populated area. It almost certainly would've been rated higher if more structures were in its path and could've easily been a killer tornado because it was heavily rain-wrapped. Berlin would've been absolutely hammered if this thing tracked slightly further east. Bowdle-like situation. The survey said at least a half-mile wide damage path.

While not rated as high and not as damaging (or killer), this may be one of the stronger tornadoes since Northwood, 2007 for North Dakota.

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Baro (or anyone else for that matter), how are the threats looking for the rest of the week (and into next week)? You're better at interpreting this stuff than me. Right now, I'm thinking the Dakotas into Minnesota could get interesting on Saturday.

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Baro, how are the threats looking for the rest of the week (and into next week)? You're better at interpreting this stuff than me. Right now, I'm thinking the Dakotas into Minnesota could get interesting on Saturday.

Ha, depends. There are a number of folks on here far better than I at interpreting potential severe weather threats. With this general pattern though, they exist everywhere...so much so impossible to key into one area. If you are asking about the northern plains though, the potential big threat Wednesday afternoon/evening as the low amplitude wave departs the N Rockies and ejects across the northern plains is not as impressive as initially thought. The positive tilt orientation and the leading prefrontal trof means mid level cooling/height falls will be lagging well behind the convergent wind shift/trof. The warm front threat may very well end up being into Canada, depending on wave speed, and even then the significant warm layer aloft poses a huge problem.

Beyond that, tomorrow looks moderately interesting across the high plains of MT/ND/SD, but the low level shear is lacking...looks more like a high based supercell threat. The next threat would come with the lagging secondary wave day 4+, but the recent guidance trends suggest that will be much flatter and a bit weaker in the midst of a somewhat stronger leading wave across Canada Wednesday-Fri.

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MESOSCALE DISCUSSION 1662

NWS STORM PREDICTION CENTER NORMAN OK

0104 PM CDT TUE JUL 19 2011

AREAS AFFECTED...FAR SERN MN...SWRN WI...NERN IA...NWRN IL

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 191804Z - 191930Z

STRONG TO SEVERE STORMS ARE EXPECTED TO INCREASE OVER THE NEXT 1-3

HOURS ACROSS THE MCD AREA. DAMAGING WINDS WILL BE THE MAIN THREAT

WITH MARGINALLY SEVERE HAIL POSSIBLE AS WELL.

LATEST RADAR AND SATELLITE TRENDS INDICATED AGITATED CU ACROSS FAR

SERN MN/NERN IA TRYING TO INITIATE OVER THE LAST 30 MINUTES OR SO

AND CONVECTIVE INITIATION IS LIKELY NOT FAR OFF. GIVEN AN EXTREMELY

UNSTABLE AIR MASS WITH SBCAPE VALUES IN EXCESS OF 5000 J/KG ACROSS

MOST OF THE MCD AREA WITH LITTLE TO NO CINH REMAINING...STORMS

SHOULD BE ABLE TO DEVELOP GIVEN A LITTLE MORE SURFACE HEATING WITH

TEMPERATURES ALREADY IN THE LOW 90S. CONVECTIVE DEVELOPMENT WILL

FURTHER BE AIDED BY WEAK CONVERGENCE ALONG A PSEUDO-WARM

FRONT/STATIONARY BOUNDARY ROUGHLY FROM THE MN/WI BORDER S/SEWD INTO

N-CNTRL IL. ONCE STORMS DEVELOP...THEY ARE EXPECTED TO TRACK S/SEWD

ALONG THIS BOUNDARY...WHICH ALSO ALIGNS ALONG AN INSTABILITY

GRADIENT SRN WI INTO NERN IL.

EFFECTIVE BULK SHEAR VALUES AROUND 30-45 KT MAY BE SUFFICIENT TO

SUPPORT SUPERCELL STRUCTURES. IN ADDITION TO EXTREME CAPE VALUES

SUPPORTIVE OF STRONG UPDRAFTS...DCAPE VALUES PER 17Z MESOANALYSIS

INDICATED VALUES APPROACHING 1500 J/KG...WHICH WILL SUPPORT STRONG

DOWNDRAFTS AS WELL. MIDLEVEL LAPSE RATES OF AROUND 6.5-7 C/KM AND

WARM MIDLEVEL TEMPERATURES WILL LIKELY LIMIT LARGE HAIL POTENTIAL.

STORMS MAY TRY TO ORGANIZE INTO LINE SEGMENTS BUT GIVEN WEAK UPPER

LEVEL SUPPORT IT IS MORE LIKELY THAT MULTICELL CLUSTERS WILL EMERGE

UNLESS A COLD POOL CAN BE ESTABLISHED.

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