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Significant Severe Weather Threat Friday 10/4


tornadotony

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at this point, just did a hand-plot of the models for comparison (with the 12z euro to come) for T+36 to T+84, and the Canadian global is the slowest of the progression eastwards at all levels with the low center coming out of southern Colorado while the NAM is the fastest with the system's progression east-northeastwards. GFS stuck in the middle. the euro yet to come.

 

it looks like the risk area for severe is getting nailed down as from what I am seeing the models have a consensus there. but it's all a timing issue now. canadian global extends the severe threat another 12-24 hours for this region and the western great lakes (and as well as the snow threat into the dakotas).

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SPC is putting out a 15% hail/wind risk for tomorrow (Thursday). Any bets on if tomorrow will have 20 hail/wind reports? Is there a significant chance for a tornado tomorrow? Or will it be one of those 2% tornado days, with no tornadoes? I will go with under 20 total hail/wind tomorrow

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SPC is putting out a 15% hail/wind risk for tomorrow (Thursday). Any bets on if tomorrow will have 20 hail/wind reports? Is there a significant chance for a tornado tomorrow? Or will it be one of those 2% tornado days, with no tornadoes? I will go with under 20 total hail/wind tomorrow

i'd say first look, i'd say within 2-3 on either side for that 20 reports mark. as for the tornado risk, i would say 2% on the 06z d1, but the chances may be upped for the 13z and 16z updates based on the 12z analyses. the day 2 and day 3 outlooks will be wholly dependent on the 12Z analyses tomorrow, so they can judge the speed of the upper low coming out of the cascades and the central/northern US rockies and have a fully-observed disturbance inside the sensing network, making the models more unified.

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Not sure I agree entirely on the 12z Canadian. It still has the H5 low centered at Cheyenne by 00z Sat and the surface low is in south-central NE. Also, verbatim, no warm sector QPF by that time. It's hard to imagine a cap bust Friday -- the extreme slow end of the guidance envelope would have to win out. If we're converging on something close to the 12z GFS, that may be the most ominous scenario, putting OMA-DMX in play with late afternoon initiation likely.

What I meant was that the 12z Canadian (and Euro too) both sped up, perhaps correcting the fact that those models were even further west just last night, while the American suite was more to the east, into or approaching Iowa by 00z Saturday.

 

With that said, I'm tentatively planning to make the trip out there on Friday, assuming the forecasts hold. It's going to be a long drive! 

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The NAM continues to come in a bit farther west...With the 18z showing a 994mb SLP near YKN 21z Fri...with quick occlusion.

Looks quite impressive near the IA/MN border, slightly further NW than the previous runs. Stronger winds aloft and a low-level jet of 50+ knots.

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I don't want to be overdramatic, but I'm struggling to think of when I've seen forecast soundings this good since April 27.

 

NAM_218_2013100218_F54_44.0000N_95.5000W

 

Right now, the ceiling certainly looks like the most impressive event for this region since 2010-06-17.

You haven't seen a sounding like that since then. The event I keep picturing is 3/29/98, the Comfrey and St. Peter >1 mi wide wedges, only the parameter space is even more impressive. The ceiling for this event is terrifying IMO, especially for an area where this kind of threat is out of season right now.
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If you're not familiar with the 3/29/98 event I referenced in the last post, you MUST read this page and look at the maps from that day:

 

http://www.crh.noaa.gov/mpx/?n=1998mar29wxpattern

 

Here's a composite loop from the Midwest that day.

 

http://mesonet.agron.iastate.edu/current/mcview.phtml?prod=comprad&java=script&mode=archive&frames=100&interval=5&year=1998&month=3&day=29&hour=12&minute=50

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Obviously the potential is sky high on Friday but I am strictly showing this to show the very impressive CAA after 0z Friday evening looking only at 850mb temps at KFSD off the 18z NAM. The 850mb temps drop 18 degrees in 3 hours. I can't remember ever seeing something like that.

 

 

Also, here is sig tor off our COD page

 

 

 

 

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If you're not familiar with the 3/29/98 event I referenced in the last post, you MUST read this page and look at the maps from that day:

I'm very familiar with this day...many friends and relatives of mine lost houses and property to that long track tornado, the comfrey, Nicollet to st. Peter line has been somewhat of a mini tornado alley in the last 25 years.

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