2014-05-07 FCST: NE, IA, , MN, KS, OK, TX

[Taylor Wright]

It appears that if the cap is less of an issue and storms can initiate, the LIs and EML will be more than sufficient for robust updrafts. However, both the NAM and GFS have the mid-level jet streak no further north than the Texas panhandle at 00z Wednesday, so I'm not sure about forcing. Storm initiation is definitely an issue with the cap that will be in place and the dryline on the NAM solution shows very little movement eastward throughout the day. Temp/dew spreads are again going to be over 25 degrees. The more I think about it, the less hope I have in this setup. If some things change, it has the potential to be the bigger of the two days, but right now the NAM shows no initiation and it reminds me a lot of last Saturday (if I remember correctly). I'm not going to be able to chase this day either way, as I have classes and I get sworn in to student senate that day. The NAM has some nice skew-ts and hodos around Wichita and further south along the dryline, so I'll keep my eye on it, but as of right now, I'm not getting too excited.

I'm wondering how the 100+ kt 200 mb winds will affect storm initiation. That's over my head as far as my meteorology knowledge. This may be too high in the atmosphere to serve as a forcing mechanism, but I would imagine it makes for strong surface convergence. That's one reason I'm not giving up hope on Wednesday. I have some concerns with Thursday regarding instability and the GFS has been bouncing around a bit with its solution, but that's for a different thread. I will send you (Francis) a pm about chasing on Thursday, maybe we can meet up. Check your inbox in a few minutes.

EDIT: Thanks mods for cleaning everything up. After looking at the 18z NAM shortly after posting this I'd like to mention that western Iowa looks to have decent potential Wednesday. The last two NAM runs have it uncapped after 21z, and hodos are very impressive there along the triple point. Definitely worth keeping an eye on.

-Taylor Wright

 

[Francis]

Yes I have been looking at Iowa as my target area for Wednesday for the past several days to go for the triple-point, my confidence in the cap breaking in Kansas is like 50/50 now, I favor Iowa for the CAPE values, moisture, EHI and helicity, everything looks good for southern/southwestern Iowa for Wednesday, I don't understand why the SPC and TWC haven't included Iowa in Wednesday's threat, actually the SPC hasn;t included anything for Wednesday, maybe they think the CAPE isn't gonna break or what?

 

[chrisbray]

Cap looks pretty stout so far. Maybe that will lessen as the day approaches, but at this point the models have been fairly consistent with the cap being unbreakable on Wednesday.

 

[Jeff Duda]

As it stands right now, I don't see this being much of an event around OK and points south. It looks almost like a carbon copy of the previous system, where insufficient moisture will get to the dryline by the end of daylight hours on Wednesday. Not just that, but the dryline will mix east of where the best mid-level flow will be, so shear will be marginal in the warm sector. The NAM currently is a bit more generous with surface dewpoints than the GFS, but both models have consistently been showing a moisture source across the current warm front in KS/MO and surrounding states where areas near the front should be seeing dewpoints exceeding 60 during the day. That did not happen at any of the surface stations in that area today (although one, and only one, came close). I suspect that moisture source is being over done. I also suspect the moisture on Wednesday is slightly overdone. Just like the previous system, the models steadily backed off on the moisture during the 24-72 hours leading up to the event. I wouldn't be surprised if we started seeing this starting with the morning models.

What's very interesting is what the 00Z NAM is doing with the cold front in IA/NE (btw, should add NE to the title of this thread). It is wrapping quality moisture around the low to the north side (the cool side) of the boundary and keeping it there through the evening. The cold front doesn't look to be packing much cold air (a big shock given how this winter went), so this is resulting in profiles with severely backed near-sfc flow, but that otherwise look like they came from the warm sector. IF this verifies, that would provide a significant amount of low-level shear. However, the better mid-level flow looks to remain well to the southwest, so I question the storm mode. It may end up being linear there given the low angle between the 500 mb winds and the front. 850 mb winds are particularly weak on the cold side of the front, too, but that does fit in with the hodographs from that area, so maybe there will still be enough shear for something interesting to happen.

 

[Mike Johnston]

The surface low, although centered in eastern CO, looks like it is taking on some characteristics of an inverted trough - which may explain some of the extensive wrap-around of moisture, northward advancement of warm front, and nice advection of high theta-e air. Actually, northern Iowa or even far southern Minnesota may have a decent combination of ingredients including backed surface winds, high dewpoints, and low-level helicity. It is pretty far removed from the upper-level trough, which looks like will have a base around the four corners region by 00z, so that's not ideal. However, I think the chances of catching some daylight convection up there may be better than along the dryline, which probably won't be until after dark. Also, the tornado parameters really are not bad. The northern and southern plays are too far removed from one another to attempt to straddle them, so one would probably have to choose one or the other by late Tuesday.

 

[Logan Karsten]

This day just screams cap bust to me. The models are performing so poorly right now with surface moisture. One reason is probably because greening up is behind for a lot of areas because of the winter. So, you have the land surface components of the models using climatological greenness information, leading to higher ET values, which overdoes surface dew points. Also, the models seem to be struggling with the surface moisture over the gulf, almost initailizing it to moist. In any event, the models struggle to break the cap in even a moist biased environment. I find it hard to believe anything would occur with realistic dew points. The problem is this last trough cleaned out the gulf pretty well. The good news is that this next system seems as though it will not achieve that.

 

[Skip Talbot]

NAM, whether or not it's valid, has been consistently showing a shot at supercells over NW IA and the MN/IA border. Moisture looks to start arriving tomorrow, so hopefully we're not dealing too much with this "just in time moisture" like on the last system.

Initial target is Spencer, IA to Blue Earth, MN. I expect storms to initially form by late afternoon on the nose of the surface low/trough on the Missouri River north of Omaha, where temps are forecast to reach the low 90's and where the convective temp can hopefully be reached despite the remaining capping issues. NAM shows LSI and CINH opening between 21z and 0z over NW IA. I'd expect initially high based storms to track N or NE and then lower as they move into the richer moisture to the NE and then turn east and latch onto the warm front. If this happens, we may see several tornadoes on the IA/MN border where directional shear is maximized along the warm front. 50+ knots of effective shear, and 300+ SRH on the warm front should maintain supercells and allow for some tornadoes. 3000+ MLCAPE should make for some large supercells too.

If the NAM is overdoing moisture return, we're probably looking at a cap bust up in IA. Everywhere else already looks like a cap bust to me including the dryline down into KS and OK. If those parameters materialize, however, we might have a nice isolated tornado machine riding the MN/IA border. The gamble is good enough for me and I'm currently in for this chase.

 

[Mike Smith]

I'm going out on a limb: I like the KS-OK border around I-35 Wednesday early evening. It looks like a collapsing (westward moving) dry line with pretty good turning from surface to 500mb. Nice height falls.

FORGOT: Winds are forecast at 100kt on the border along with difluent flow.

 

[Mike Johnston]

Still like the looks of the northern Iowa / southern Minnesota are for convective initiation. However, I did fail to mention one concern in my post yesterday. That is: LCL's look a little high. Perhaps 1,800 to 2,200 meters at 00z. That's a little too high - don't you think? Storms might be high-based. Reduced tornado potential, maybe more of a hail threat. I do admire Skip, Francis and others that are going to look at it, though. Good luck to you all.

 

[dixiealleyspotter]

Wish I could make it that far North... definitely not that hardcore.

I will be one of the chasers down south tomorrow. I'm seeing the cap bust at just the right time and just the right place... my target as of now is between Lubbock and Wichita Falls, TX at 3pm.

Will be monitoring vis satellite to hone target and be ready for initiation around 5pm. Cells will have to organize and move east (motion looks to be NE@20-25mph) into more instability and richer surface moisture.

If they can hang on Helicity looks to move in around 7pm and we could have a sunset surprise.

 

[Skip Talbot]

LCL's look a little high. Perhaps 1,800 to 2,200 meters at 00z. That's a little too high - don't you think?

LCLs are sky high where storms would be initiating on the surface trough/thermal axis. Initial cells will be very high based if they can go up in the warm sector. As they move north east, into the cooler, moister airmass to the northeast, bases should lower. LCLs are a much more respectable 1200-1000 on the IA/MN border ahead off the nose of the low pressure at 0z.

In order for this setup to work, a cell has to go up on that axis of strong heating in eastern NE and move toward the better moisture and backed winds to the northeast in southern MN. If we don't get a sustained updraft here, I don't see any shots at tornadoes. There's one specific spot where the cap is open, some low instability is present, and the shear is maximized. The NAM has been consistently highlighting the Spirit Lake, IA area and northeast into MN. Adjacent areas down the warm front have decent parameters too, but I'm not seeing the source of lift or a specific spot for initiation (maybe way out west in SD/NE where the midlevel lapse rates are steep and there's some height falls?). SPC has no mention of this in their outlooks of surface based storms in the warm sector, only elevated stuff north of the warm front. The convective plots are silent across e NE and nw IA through 0z. Anyone chance a chase up there could be strongly looking at a cap bust. The cap plots have been trending negatively recently, making it doubtful I'll pull the trigger on this. The 18z NAM is still a little hopeful though with a nice hole in the cap at 0z and some extreme instability at 0z. Could be a pleasant night in northern Iowa, or maybe there will be one of those huge isolated supercells tracking across the state with nobody on it?

The dryline storms across KS, OK, and TX will probably be largely elevated, or at least have a minimal tornado threat yet beyond some spinups or spouts due to the capping down there.

How's this for a wishcast?

 

[Chad Alcares]

The Ogalalla, North Platte, Broken Bow area of Nebraska intrigues me. The moisture is on the wrong side of the conceptual model for severe weather... but it's there nonetheless thankful to a fetch north and then west tonight into tomorrow morning. And there is SBCAPE near and north of that dryline thingy. I like the chances of convective initiation with the higher elevation west of Broken Bow than further east, dewpoints don't have to be 60 in this area to get a good tornadic storm. Enough Bulk Shear to sustain updrafts... shear profile is parallel to that dry line thingy so storms should propogate off of it. Helicity is... meh, but... it's the Sand Hills. Seen crazier things out there, and since I have the day off might as well check it out. I'm liking that feel that anything I see in IA, NE, SD, MN... Those north/northeast winds may turn people off... but I'm ignoring that as I don't see a wedge of cold air cutting off updrafts with that wind, I see moisture inflow sustaining surface based thunderstorms.

 

[dixiealleyspotter]

0Z NAM LCL

If this holds true there is certainly a chance in TX....



And the cap looks to erode just in time.

This Sounding is NAM projected from Wichita Falls @ 0Z....




And the Hodo.....



I'm pretty sure that everyone here has much more forecast knowledge and experience. And I know that this isn't the thread for questions...

But what am I missing? Why isn't Texas in play tomorrow?

My viewpoint from my level of knowledge/experience tells me that there is a real chance of a short lived, beautiful tornado at sunset in TX tomorrow.

And I want to chase!!!

Edit: sorry Mods, first try inserting images. Didn't work how I planned

 

[Brandon Jenkins]

View attachment 8404

0Z NAM LCL

If this holds true there is certainly a chance in TX....

View attachment 8405

And the cap looks to erode just in time.

This Sounding is NAM projected from Wichita Falls @ 0Z....


View attachment 8406

And the Hodo.....

View attachment 8407

I'm pretty sure that everyone here has much more forecast knowledge and experience. And I know that this isn't the thread for questions...

But what am I missing? Why isn't Texas in play tomorrow?

My viewpoint from my level of knowledge/experience tells me that there is a real chance of a short lived, beautiful tornado at sunset in TX tomorrow.

And I want to chase!!!

Edit: sorry Mods, first try inserting images. Didn't work how I planned

TX is not out of play tomorrow by any means, but with temperatures sky high there is no doubt that storms firing off the dryline will be elevated in nature and fighting a rather potent capping inversion as they move east. Of course, there is always the chance of storm scale cooling and subsequent lowering of LCL's as temps fall just prior to sundown but the window is narrow. All of that aside, convection allowing models are somewhat confident that this area will be the initial focus of convection tomorrow so discrete elevated supercells are a distinct possibility from just SW of ABI north into SW OK. I think there is a shot in the dark chance at a few brief ropes with the more intense cells tomorrow but I wouldn't make the drive anticipating that outcome. Know that isolated (and likely elevated) storm structure will be the primary show tomorrow, with the oddball chance at a tornado.

 

[Marcus Diaz]

There should be storms in TX and SW OK today, but they will be elevated in nature for quite some time. The weak low level shear will support splitting cells for most of the storms life. The dryline looks to start marching west near sunset, which is good for any sustained cell out there. And as the evening wears on, low level jet should start cranking. I don't see why a storm can't get rooted down and right turn to become a nice LP supercell around sunset today. Maybe even squeak a weak tornado or two just before we lose light completely.