5/30/08: FCST: KS/MO/IA/NE/MN/WI/IL/IN/OH/MI

[John Sickels]

As highlighted by SPC, possible large-scale outbreak of severe weather on Friday, May 30th, across a broad swath of the plains and Midwest.

 

[Kevin Crawmer]

Just to add to this....strong upper level flow. 50-60 kt over the countries midsection from KS to IN/OH. Directional shear does not look that good at the moment, but speed shear does. If my memory serves me correct, there wasn't good directional shear in IA on Sunday was there?

Anyways, LIs are in the neighborhood of -12 and 4000+ CAPE. Right now it looks like NE KS, SE NE, most of IA, and W IL look to be primed for action on Friday.

 

[George Tincher]

Looking at some samplings from the GFS forecast soundings (the one above being from Peoria at 00z), I'm not seeing much in the way of directional shear. So if that is how things pan out, the tornado threat may not be too great. But this is still a long way out. Lots can change.

But regardless of whether the tornado threat will be low or high, I do feel that severe weather will be widespread on Friday (and again on Saturday). There are lots of things to like about the setup as the GFS paints it.

1. Steep mid-level lapse rates
2. Very nice lifted indices
3. Strong deep layer shear
4. Good CAPE
5. Breakable cap

So again, with the cold front plowing into this very large area with favorable conditions in place, at the very least, you're likely to see a classic late Spring midwest squall line with a wide spread wind damage threat. Increase the directional shear just a little over what the models are currently forecasting and things could get very interesting.

Friday certainly is worth keeping an eye on. But that's about all I am willing to try to pin down at this moment because we know the models will probably flip-flop back and forth several times between now and then. But as of right this minute, based on the limited data I've seen, I would favor NE KS for the best area of tornadic potential. The Kansas City area is showing the best directional shear of any area within the broad outlook that I've seen, with very strong CAPE.

 

[Colin Davis]

Looking at some samplings from the GFS forecast soundings (the one above being from Peoria at 00z), I'm not seeing much in the way of directional shear. So if that is how things pan out, the tornado threat may not be too great. But this is still a long way out. Lots can change.

But regardless of whether the tornado threat will be low or high, I do feel that severe weather will be widespread on Friday (and again on Saturday). There are lots of things to like about the setup as the GFS paints it.

1. Steep mid-level lapse rates
2. Very nice lifted indices
3. Strong deep layer shear
4. Good CAPE
5. Breakable cap

So again, with the cold front plowing into this very large area with favorable conditions in place, at the very least, you're likely to see a classic late Spring midwest squall line with a wide spread wind damage threat. Increase the directional shear just a little over what the models are currently forecasting and things could get very interesting.

Friday certainly is worth keeping an eye on. But that's about all I am willing to try to pin down at this moment because we know the models will probably flip-flop back and forth several times between now and then. But as of right this minute, based on the limited data I've seen, I would favor NE KS for the best area of tornadic potential. The Kansas City area is showing the best directional shear of any area within the broad outlook that I've seen, with very strong CAPE.

GT, I think it's key to remember that it's very rare that IL has directional shear with a setup this dynamic. Oftentimes, we're forced to rely on boundaries from previous cells to provide the low-level turning, since, usually, we get the hand-me-down MCSes from the night before.

As for the actual forecast part, I can't add much, since I frankly haven't seen a thing for this setup. I've been paying close attention in the last 24 hours to Thursday's NE setup, though, hoping that I can chase Thursday and follow the system back home on Friday. As this appears more likely, I'll throw in a bit more about both days.

 

[Brandon Sullivan]

As Kevin said some really nice instability going to be there for this one.

GFS progs 6KM Deep layer shear values around 55 KTS over the IA/MO border.

NAM brings 7 sig tor over IL..

Certainly bears watching..

Wish I could see a little more CAPE over IL..

 

[Brandon Sullivan]

Well just a quick 00z Wed Model Run Update.

Actually having some trouble getting any 00z data, but from what I gather, I like what I can see..

NAM appears somewhat ominous showing 4000+ CAPE Developing by 00z Sat over SC IA and NC MO and some 3000+ Values into western IL.

Since I am not getting much data, I can't look deep into Hodo's but the best helicity is focused over the Jet Axis from Central MO into central IL and southwest into OK. Looks like CAPE/Shear could become more co-efficient this time..

I would expect some enhanced probabilities on SWODY 3 Tomorrow.

 

[Darrin Rasberry]

Those winds are pretty horrible IMO, but they weren't exactly behaving well at the surface here Sunday, either. Still though, they look pretty unsuitable, and given how efficiently the WRF breaks the cap I'm going to take a potshot at brief discreet moments - much like Sunday here minus the Parkersburg monster - followed by quite possibly a derecho event as the low keeps trucking east to Canada without even bothering to stop for a bathroom break, and the resulting shifts push the system together into a terrible, windy eastern U.S. tour.

Right now my forecast chase area is southern Iowa INVOF I-35 to catch them before they line up.

 

[Brandon Sullivan]

Well just a quick 00z Wed Model Run Update.

Actually having some trouble getting any 00z data, but from what I gather, I like what I can see..

NAM appears somewhat ominous showing 4000+ CAPE Developing by 00z Sat over SC IA and NC MO and some 3000+ Values into western IL.

Since I am not getting much data, I can't look deep into Hodo's but the best helicity is focused over the Jet Axis from Central MO into central IL and southwest into OK. Looks like CAPE/Shear could become more co-efficient this time..

I would expect some enhanced probabilities on SWODY 3 Tomorrow.

 

[Colin Davis]

Well just a quick 00z Wed Model Run Update.

Actually having some trouble getting any 00z data, but from what I gather, I like what I can see..

NAM appears somewhat ominous showing 4000+ CAPE Developing by 00z Sat over SC IA and NC MO and some 3000+ Values into western IL.

Since I am not getting much data, I can't look deep into Hodo's but the best helicity is focused over the Jet Axis from Central MO into central IL and southwest into OK. Looks like CAPE/Shear could become more co-efficient this time..

I would expect some enhanced probabilities on SWODY 3 Tomorrow.

I guess I don't see what others see...because personally, I think it looks like hell, lol. Winds completely unidirectional...the only turning I see at all is the GFS solution...which brings 925mb and SFC both to the NORTHWEST, at a brisk 5kts at the surface and not anywhere close to the area of best instability.

Unless there are some boundaries from previous storms in place, I don't expect much at all out of Friday's setup. Bow echoes for all, lol.

 

[Mike Peregrine]

Friday will no doubt change significantly after the results of whatever happens Thursday. As it stands now, I would take a closer look at Friday if the winds shape up from what looks to be largely unidirectional at this point. Also, storm motion may be quite difficult if models are anywhere close to verification.

Moisture transport appears highest from northeast Kansas across most of the northern half of Missouri. GFS shows very messy surface winds across northern Missouri/Iowa, which should hopefully resolve better with time. Models agree on strong midlevel flow ... 500mb wind is progged out of the west at 55kts per GFS ... NAM is forecasting storm motions of 40kts out of the west/northwest (that would be interesting). There appears to be plenty of CAPE in place, which is always good.

It's enough to keep an eye on, but not enough for me to get excited about yet. Maybe some better winds will develop back to the west over NE Kansas on Friday. There is plenty of CAPE back there. Maybe it will be enough to do the trick west of EAX, for a little while at least. I'm thinking severe, but not seeing tornado potential at this point.

 

[Darrin Rasberry]

I guess I don't see what others see...because personally, I think it looks like hell, lol. Winds completely unidirectional...the only turning I see at all is the GFS solution...which brings 925mb and SFC both to the NORTHWEST, at a brisk 5kts at the surface and not anywhere close to the area of best instability.

Unless there are some boundaries from previous storms in place, I don't expect much at all out of Friday's setup. Bow echoes for all, lol.

The reason why the winds are so awkward is because of that closed low progged over the great lakes; of course, areas of low pressure such as that will suck in wind (like a gigantic vacuum cleaner) and when they truck along like that over New England into Canada, they'll drag those winds with them and make them linear over the heights that matter. That's why you'll see very likely a bow echo out of this feature if the models turn out right, or even a derecho. If the low gets low enough and trucks fast enough, and the storms it drags along in its wake get strong enough, we may be seeing one of those high-risk, PDS SVR watch events unfold, but it seems a little too early in the season for that IMO. Nevertheless, those lines will be their own little cold fronts, and, if strong enough, they can manipulate the winds by themselves just enough to create embedded tornadoes. It's just something I'd prefer not to chase.

Despite all this, there still could be enough shear in place, or, like mentioned earlier, a favorable OFB or something, to have some discreet action before everything is swept away to freaking Maine. We'll have to see how the "sloppy seconds" unfold for Thursday's action, but whatever takes place, I'm gonna wager this to be a pretty difficult chasing setup.

 

[Brandon Sullivan]

Despite all this, there still could be enough shear in place, or, like mentioned earlier, a favorable OFB or something, to have some discreet action before everything is swept away to freaking Maine. We'll have to see how the "sloppy seconds" unfold for Thursday's action, but whatever takes place, I'm gonna wager this to be a pretty difficult chasing setup.

Indeed. Indeed. This setup I think will be hard to forecast and hard to chase. I think that any OFB or local boundaries could be enough for a storm to become tornadic, and with the CAPE in place it is not out of the realm of possibility.. Also, the prime time for tornadic activity will be before things line out...

My target tommorow is going to be wherever the OFB sets up.. Which isnt very specific at this time... But thats what I have to offer..

 

[Eric Graham]

I'm liking this setup just because it'll prety much be in our back yard after 3pmish on Fri. Forcasting more of a derecho event than anything but hey I'll take what can get. Temps forcasted in the 80s with pretty much clear skies all day and very humid conditions predicted as well. More later....

 

[Andrew Pritchard]

At this point I'll be looking to play an OFB that should end up around Interstate 72/74.

We'll probably see the MCS die out across central IL in the morning draping the boundary along it's path back into northern Missouri. With clearing being quicker and more substantial further west I think we'll see development back towards northern Missouri and southern Iowa first.

Not sure how much tornado potential we'll see since obviously directional shear is pretty poor. OFB may help that a little, but more than likely we'll just see upscale development into another SE'ward propogating MCS that will track towards the St. Louis area towards evening.

I think we're looking at a high wind event with the areas most at threat being eastern Missouri, and then western and the southern half of Illinois. Strong H5 jet will kick in so the line(s) should be quick moving and may drop a few significant wind gusts. I may go out just for some convective fun to hold me until the next system digs in next week.

Northern Indiana and southern Michigan may also be at risk if enough instability develops ahead of the decaying MCS and we see regenerative convection on the leading edge of that. There may be a somewhat greater tornado potential in this area with the strong low level jet already being in place. Would still like to see a little more turning before I'm sold on that one though.

 

[Eric Graham]

MOD risk for tomarrow for ILL and western IN for tomarrow. Nice amount of instabillity is in the air with all the other ingredients falling into place. NWS stating that possibillity of "one or two tornadoes associated with the squall line might occur." Still looking at this as a strong wind/derecho event however.