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Significant Severe Weather Threat Friday 10/4


tornadotony

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My old friend is still being run...Given the Marine layer this looks more likely to me.  The moderate outlook IMO may be dropped entirely, or localized along the Missouri River near Omaha possibly as far north as Sioux Falls.

 

hotlink:

 

cape_t2sfc_f21.png

 

I'm thinking they narrow the corridor for the mod risk, say between US 18 and I-80 in IA, from I-29 to maybe US 63, with the slight risk kept where it is for the hail risk.

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I don't know what the whole marine layer thing is, and I don't think the MDT will be dropped -- but we might see a reshaping of the MDT area. A slower front and perhaps influence of widespread convection up north may put the higher focus area closer to I-80.

 

Which is not a good thing considering that region/corridor is substantially more populated than the area, say the NAM, is targeting.

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I don't know what the whole marine layer thing is, and I don't think the MDT will be dropped -- but we might see a reshaping of the MDT area. A slower front and perhaps influence of widespread convection up north may put the higher focus area closer to I-80.

 

When the air mass is flowing over one or more of the Great Lakes, the air has a tendency to stabilize and the area west of Lake Michigan (pretty much all of Wisconsin and even further) tends to have limited severe weather with the easterly flow. I know around here, it is rare to have severe weather with an onshore flow.

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I don't know what the whole marine layer thing is, and I don't think the MDT will be dropped -- but we might see a reshaping of the MDT area. A slower front and perhaps influence of widespread convection up north may put the higher focus area closer to I-80.

 

Gfs at 21z look at the NE winds over Sioux Falls and look where they originate from, like I said before if a mod risk should remain it will be very near the Omaha area.

 

gfsUS_sfc_temp_021.gif

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Gfs at 21z look at the NE winds over Sioux Falls and look where they originate from, like I said before if a mod risk should remain it will be very near the Omaha area.

 

Not to be pedantic, but who said anything about Sioux Falls, and note that the GFS graphic there still has 75-80˚F to the IA/MN border with a southerly component to the sfc winds.

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When the air mass is flowing over one or more of the Great Lakes, the air has a tendency to stabilize and the area west of Lake Michigan (pretty much all of Wisconsin and even further) tends to have limited severe weather with the easterly flow. I know around here, it is rare to have severe weather with an onshore flow.

So the Great Lakes have moved into srn MN and nrn IA?  Wow, a lot has changed since I moved south.  I'm gonna have to check that out.

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I'm beyond impressed with tomorrow for eastern NE into western IA. Modeling tonight is converging toward a deep H85 low with a strong, backed LLJ over much of the risk area. The only real fly in the ointment now in my eyes is the cold pool from tonight's activity. With such a wrapped-up system, though, I'd have to imagine the warm sector gets entirely rebooted by showtime tomorrow afternoon. Climo is really the only thing putting doubts in my mind for a top-end ceiling.

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I'm beyond impressed with tomorrow for eastern NE into western IA. Modeling tonight is converging toward a deep H85 low with a strong, backed LLJ over much of the risk area. The only real fly in the ointment now in my eyes is the cold pool from tonight's activity. With such a wrapped-up system, though, I'd have to imagine the warm sector gets entirely rebooted by showtime tomorrow afternoon. Climo is really the only thing putting doubts in my mind for a top-end ceiling.

 

Well, FWIW, climo didn't stop a likely sig-tor from happening nocturnally earlier in NE.

 

New D1 maintains moderate with 10% hatched-tor area.

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When the air mass is flowing over one or more of the Great Lakes, the air has a tendency to stabilize and the area west of Lake Michigan (pretty much all of Wisconsin and even further) tends to have limited severe weather with the easterly flow. I know around here, it is rare to have severe weather with an onshore flow.

 

Yes, and I'm very familiar with the marine layer here in California -- but we're talking about southern MN... pretty far from any large, deep bodies of water.

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Well, FWIW, climo didn't stop a likely sig-tor from happening nocturnally earlier in NE.

New D1 maintains moderate with 10% hatched-tor area.

Area is not changed much from previous update, if anything squashed just a tiny bit to the south. 45% hatched large hail for the same area. It should be a wild day with some significant severe reports. Only question to me is that, are there only a few isolated reports, or do the high-end forecasts verify with a small scale outbreak? The extent of AM clouds/debris will be one factor...
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I'm beyond impressed with tomorrow for eastern NE into western IA. Modeling tonight is converging toward a deep H85 low with a strong, backed LLJ over much of the risk area. The only real fly in the ointment now in my eyes is the cold pool from tonight's activity. With such a wrapped-up system, though, I'd have to imagine the warm sector gets entirely rebooted by showtime tomorrow afternoon. Climo is really the only thing putting doubts in my mind for a top-end ceiling.

 

That's really my main concern as well, not necessarily just from tonight but development tomorrow. The models have been fairly consistent in developing copious junk convection over IA through mid-morning at least. As I alluded to earlier I wouldn't be surprised to see the warm front end up not as far north as progged.

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I'm beyond impressed with tomorrow for eastern NE into western IA. Modeling tonight is converging toward a deep H85 low with a strong, backed LLJ over much of the risk area. The only real fly in the ointment now in my eyes is the cold pool from tonight's activity. With such a wrapped-up system, though, I'd have to imagine the warm sector gets entirely rebooted by showtime tomorrow afternoon. Climo is really the only thing putting doubts in my mind for a top-end ceiling.

100% agree.

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HRRR is almost into range. 4z buys us to 19z. At that point most of the junk from the AM has exited Iowa. Warm front is basically 2/3 the way up the state with SBCAPE as high as 3800 (FWIW) in extreme eastern NE. Elsewhere in central IA skies go SCT and some convection is just initiating at the 15th hour/19z.

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The reason why this is more of an Iowa threat than a Minnesota threat is due to the ongoing convection that is occuring now, this will limit the Northward surge of the warm front into Minnesota. It has nothing to do with marine layers like someone mentioned earlier, it has everything to do with ongoing convection and the warm frontal progression.

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A few red flags flying...moisture doesn't want to move out and the last few runs of the HRRR don't show much of anything at all. Very curious how SPC plays it at 13z.

It's only 1245 UTC...all the models had precip where it is right now.

 

And this is "not much?"  This is a string of tornadic pearls.  Keep in mind that there's often a time lag later in high-res model runs, so this is probably a couple hours slow:

 

cref_t2sfc_f15.png

 

hlcy_t2mx16_f15.png

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