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November 5th, 2017 Severe Weather Event


IllinoisWedges

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NAMs have a good convective signal on the cool side of the front.  Much of the attention is being paid to the warm sector for obvious reasons, but could also have a decent elevated hailer threat in that strongly sheared environment (and assuming sufficient elevated CAPE)... especially for this time of year.

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7 minutes ago, Hoosier said:

NAMs have a good convective signal on the cool side of the front.  Much of the attention is being paid to the warm sector for obvious reasons, but could also have a decent elevated hailer threat in that strongly sheared environment (and assuming sufficient elevated CAPE)... especially for this time of year.

I have a new car, I can't yawn at this prospect fast enough :lol:

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Just now, Stebo said:

I have a new car, I can't yawn at this prospect fast enough :lol:

I'm always in the mood for something out of the ordinary, and it would be out of the ordinary for me.  Haven't seen hail at this time of year in quite a while, and when I have it's been like pea-marble size.

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Just now, Hoosier said:

I'm always in the mood for something out of the ordinary, and it would be out of the ordinary for me.  Haven't seen hail at this time of year in quite a while, and when I have it's been like pea-marble size.

I know, its just the prospect of elevated hailers usually ends up underwhelming.

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Was trying to think of the last day 3 outlook in the fall that was as beefy as this one (in this region), and I wonder if you'd have to go back to the 10/18/07 event.  That one was 45% on day 3.  Hell, 11/17/13 wasn't even hatched on day 3.  I realize this depends on situational and model confidence and who's doing the forecast, but still, not very common to see an outlook like this.

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5 minutes ago, StormChaser4Life said:

If Nam is right man there will need to be major changes to the outlook. Nam really struggles to get the warm sector north 

Have to wonder if the NAM is onto something, or simply wrong. The 12z RGEM is at least 100 miles farther north with the low (northern MO) and warm sector (to the IN/MI border).

The upcoming Euro will be very telling. If it continues to lean toward the NAM, then the northern solutions would seem to be increasingly unlikely. 

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3 minutes ago, Quincy said:

Have to wonder if the NAM is onto something, or simply wrong. The 12z RGEM is at least 100 miles farther north with the low (northern MO) and warm sector (to the IN/MI border).

The upcoming Euro will be very telling. If it continues to lean toward the NAM, then the northern solutions would seem to be increasingly unlikely. 

NAM also looks to be on the slow side.

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I'm not sure if 11/14/11 was mentioned, but that seems to be a reasonable analog that doesn't lie on one extreme end of the spectrum. That involved a weak frontal wave moving across central IL/IN within several hail reports and a few isolated tornadoes. The kinematic and thermodynamic fields look similar to the progs for Sunday, although I will go back to the capping inversion (looks a bit more pronounced this go-around), which may ultimately limit or prevent open warm sector storm development. Nonetheless, watch the warm front and triple points for a relatively higher tornado potential. Wind fields become more unidirectional near the cold front, but even there a narrow window for semi-discrete storms may exist. Of course, this is an evolving forecast and things may change, but I think the below maps show a reasonable "estimate" of what we may be looking at for Sunday. A more wound up solution than the consensus could result in a more significant event. 

111114_rpts.gif

19_rgnlwarn.gif

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22 minutes ago, Hoosier said:

So to summarize the 12z runs from farthest south to north, the NAM is farthest south, followed by the ECMWF.  Then the GGEM and GFS.  As Quincy noted, the RGEM out to 48 hours looks like it may be headed more toward the northern side.

Thanks for the summary. Appreciate it. Doesn't NAM often have a cold bias? I guess if we don't have a good sfc low though we won't have as good llj response to really get the warmth and moisture north. Def not a fan of this zonal jet. Need some amplitude

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12 minutes ago, StormChaser4Life said:

Thanks for the summary. Appreciate it. Doesn't NAM often have a cold bias? I guess if we don't have a good sfc low though we won't have as good llj response to really get the warmth and moisture north. Def not a fan of this zonal jet. Need some amplitude

Depends on what you're talking about. Models (not just the NAM) frequently lowball temps in the warm sector at this time of year.  As far as the NAM placement/track of the surface low/warm front, it could be right but it's on the southern end at this point.

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1 minute ago, Chambana said:

Excuse my rookie comment, but as far as comparison for 11/17/13 it’s nowhere bear that magnitude right? 11/17/13 was a neg tilt trough, with a much stronger deepening surface low,and this setup is a positive tilt trough, with a weaker low.  

Correct.  The CAPE and main threat area look similar, but that's about it.

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1 minute ago, Hoosier said:

Yeah, this run has a 45 contour in IL/western IN, up from the previous run.

I would be leery of it being a consideration of moving north instead of just better model consensus. The MSLP projection underneath the Tor ingredients image would suggest a slight tick faster this run compared to previous run of SREF.  I do think it is significant that it is getting better agreement though.

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Yea I am not feeling this setup as much as I was before. Likely will still be chasing because it is Nov and is relatively close. There will be severe storms but the magnitude and tornado threat is obviously depending on strength and placement of low and degree of destabilization. Shear is abundant and obviously won't be an issue. The degree of capping of lack of significant height falls makes me wonder if warm sector storms will form or will storms stay confined to the boundaries

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