6/5/08 FCST: TX/OK/KS/NE/MN/IA/MO

[Jeff Snyder]

Anyways, according to the basic data above, I am guessing that Central OK may get the undercard to the main event that everyone is thinking is going to happenng in nw-ern MO and SW-ern Iowa. I am pretty skeptical that things are going to play out that far north.

It's possible that things may open up farther south, but, geez, the mid-level temps may well be very warm! The NAM is currently indicating -2 to -4C 500mb temps across western OK Thursday evening, and the -4C 500mb isotherm extends all the way to the MO/NE/KS/IA border region. A little lower, hot 700mb air will be pulled northward towards eastern IA and IL on stiff southwesterly 700mb flow, with >16C 700mb air from SPS to northeastern MO. Some cooler 700mb air will be located along the front and northern part of the dryline, and sustained convergence will likely help with initiation. Regardless, per the 12z NAM valid Thursday evening, capping appears as though it will be very strong SE of a line from Shamrock, TX, to Salina, KS, to Des Moines, IA. The 12z GFS is considerably farther south w/ the primary sfc low and the position of the cold front, and it's considerably cooler with the 500mb and 700mb temps, two things that I would certainly welcome being a chaser based out of OUN. I don't have access to much in the way of ECWMF graphics, but what I can see (on CoD) would seem to indicate that a higher-amplitude trough would support some cooler mid-level air; the ECMWF from last night is considerably deeper and more compact (i.e. showing a larger meridional component to the mid-upper level flow) than both the GFS and NAM.

 

[Donald Giuliano]

You should have some moisture concerns. Substantial mixing has been occurring the past couple of days inland from the Gulf Coast. This will likely improve in the next two days, but we'll still have some lingering effects.

It's June and it's getting pretty warm in the warm sector. With post-dryline temps well over 100 F, and pre-dryline temps in the lower 90s, it would be nice to have low-mid 70 Tds. We might scrape up low 70s right along the warm front. I don't think LCL heights will be so high as to kill the tornado threat, but this is one reason (along with the cap) why you don't see as many June warm sector outbreaks (compared to May).

Rich T.

LCLs, cap, mixing, etc. could definitely be a problem this week but I'm still keeping an eye on the situation regardless. Hopefully these problems just mean we'll only be seeing mile-wide stovepipes instead of wedges!

 

[John Hudson]

Looking at the GFS, the very best instability still appears to be W to NW IA; the cap just gets huge south of that.

Although surface winds will have a bit more of a S to SW component than I'd like, I strongly believe this will kick off in NW IA and into SW MN, if nothing major changes between now and Thurs.


John

 

[afischer]

FWIW, there appears to be seasonably rich boundary layer moisture now over much of the central low plains per the 00Z RAOBs. In particular, Topeka shows a 100mb mean layer dewpoint of 21C... quite nice. Obviously this moisture profile will change between now and Thursday, with the EML sweeping in from the southwest tonight and squashing the moisture depth... elevated moisture advection into thunderstorms mainly north... diurnal mixing... etc. It will be interesting to see how it pans out. I felt overall that for northern targets, which is what I've been eyeballing the past couple days on the models, the 12Z GFS soundings Thursday aftn/eve appeared pretty reasonable (deep moisture and surface Tds right around 70F.)

 

[Mikey Gribble]

I'm not so much worried about the quality of moisture, but I am worried about the location of it. As Rich mentioned what we really need for a good tornado threat is mid 70's, but that probably isn't going to happen. Upper 60's looked really good when surface temps were only in the mid 80's, but now we are hitting the 90's. We need to keep the t/td spread inside 20 degrees to maintain a decent tornado threat.
Veering surface winds early in the day will likely keep the better moisture well out over the warm sector ahead of the dryline. I don't think this will be a problem along the warm front where low level winds should parallel the boundary earlier in the day. Moisture pooling should keep low 70 td's along the warm front and LCL's should be lower as a result. This leads me to believe the warm front will hold slightly better potential. But then when I start to look at the shear profiles I really like the screaming 850mb winds ahead of the dryline. The mitigating factor for tornado potential along the dryline is high LCL's (like I just mentioned), but if storms can fire early enough in the afternoon, 40kt storm motions should quickly carry them into the better moisture and as surface temps drop in the late evening I think there will be a window where tornadoes are likely across Kansas (ahead of dryline). Pinning down the best tornado potential along the warm front is pretty much impossible ATTM IMO due to significant model differences. I posted more on the forecast on my blog if you're interested http://loadedgunchasing.com/blog.html

 

[Darrin Rasberry]

For Iowa of course the big question is this: what happens on the 4th, and how much "stuff" happens? If we get that sloppy-seconds MCS again, this might be limited to a far-northern potential up in Minnesota (although, it could also leave an OFB if destabilization can occur enough in IA), and capping/Td vs T will be an issue further South as illustrated already.

Right now I'm going to draw an extremely preemptive, soon-to-change, huge box from Sioux City to Waterloo to the Twin Cities, back diagonally down to Sioux Falls, as this is probably the best combination of territory/potential ATTM.

 

[afischer]

I sure hope we don't need mid 70s F surface dewpoints in the northern target, or I am gonna stay home. I agree, for southern targets, dewpoints around 70F might not cut it given the forecast warmth of the airmass. On the GFS soundings (take it with a huge block of salt), 68-70F surface dewpoints contribute to nice low-level thermodynamic properties for tornadoes in the northern targets (MLLCLs around 1000m and 3km CAPEs > 100)... off the 12Z GFS, that target generally being the western 1/3 of IA.

 

[Dustin Wilcox]

I'm not a huge fan of IA on Thur per the latest 0Z runs I have seen. Per the 12KM I think the show will be in SC to C KS on Thursday, the 12KM hits the Wichita area pretty hard with the storm of the day coming out of that area and moving North-East riding the nose of the 55kt LLJ under a nice 60-70kt H5 Wave with substantial cooling, the sfc and 850 jet is actually backed compared to the super veered jet in IA. Provided this run verifies with sfc features and is accurate with mid level temps, I would say SC to C KS will be the place to be Thur....

 

[afischer]

Northern targets looking pretty gross on the 00Z GFS, with secondary cyclogenesis no longer forecast to develop/lift NNE toward Sioux City (which looked really really good on previous runs)... instead, a strung out quasistationary front parallel to the deep layer shear vectors is now forecast, along with veered surface flow and a weaker LLJ. I still like the northern targets on the 00Z NAM-WRF (provided pre-event elevated stuff clears out like Darrin mentioned), but don't trust it much with the primary system still offshore and yet to evolve. The ECMWF has consistently given an even different solution... more meridional and less progressive. Not sure how this all compares with any ensemble data. Things are about as clear as mud to me right now.

 

[Mike Hollingshead]

The south central KS target looking pretty intense on the 18z NAM. More likely to get the mid-levels veered a bit more down there, and probably better sfc backing with the secondary deep sfc low. Forecast soundings look scary well into the night.

p28 at 0z

HUT at 0z

WLD at 3z

WLD at 6z

If they do fire in the drier air, it's not going to take them long to get into the juice, with a 75 knot sw mid-level jet. Here's hoping for a storm near the sw-ne highways 56, 61, or 2(though not on, for obvious reasons). Guess that is one thing the area has going for it.

 

[Derek Weston]

If the new Day 2 verifies then I'm going to say with a heavy heart that it's the death knell for up here. Looks like I'll be staring at my shoes and shuffling my feet for KS, but maybe I can get lucky enough with NC to NE Kansas .... I'll see once DuPage integrates the 00Z runs.

Based on latest NAM....
Got an area across very far E NEB/W IA/SW MN that still looks interesting to me for the northern play. Cap shouldn't be too bad -- we've got an area of cooler 700s through this region -- further east in Iowa would seem to be cap bust potential.

Favorable directional shear and possibly some decent CAPE making its way north -- still want to see exact placement of warmfront though. And of course whatever issues earlier MCS junk might bring us.

 

[Adam Lucio]

Derek you almost read my mind with the target area I was thinking about for the northern play. GFS looks to have a breakable cap by 0z Friday with the warm front draped along the NE/SD and adjacent IA/MN border. Winds also look slighty backed in northern IA. I think the northern target will offer better t/td spreads as long as we can get the juice there.

It looks like the better juice will be further east under the stronger cap...CAPE looks really good around the same areas as well with values approaching 3000 j/kg.

NAM seems to be a little less with the dews and wants to keep the surface low a tad to the west.

Right now I like the "4 corners" region between SD, MN, IA and NE, around Sioux City....I wish the river wasn't there but I think that is where I will set a preliminary target zone for the northern play. Live conditions, front placements, crapvection influences as well as later model runs will require further adjustments, but overall I like what I am seeing!

 

[John Hudson]

Indeed, the 00Z WRF actually shows surface winds backing a little better now on the northern play. Better juice is to the south, but so is the cap.

Sioux Falls area shows very favorable sounding forecast with lower LFC's, but I'd like to see a little more improvement in the hodograph. Maybe over the course of the day things will change, but I'm very close to packing the gear for SD ATTM.


John

 

[Chris Lott]

Can't afford to drive that far north, but I am keeping an eye on parts of NW TX for tomorrow afternoon. There are some indications that the cap could break, and if so, I'm liking Vernon,TX for a target. I think some discrete cells may form along the dryline Thursday evening, and if so they will have plenty of juice to work with, and some descent shear as well, although I don't see these being big tornado producers. Vernon sounding looks pretty good tomorrow afternoon assuming the cap breaks.

 

[Mike Hollingshead]

Yikes is the 12z NAM insane for tomorrow. 700mb temps spread ne tonight through tomorrow morning capping things off and hopefully keeping the warm sector clear. Low level jet never really veers horribly, then HOWLS out of the south by afternoon/evening. Mid-level cooling comes in late afternoon, accompanied by a 75 knot sw mid-level jet(above southerly 50+ knot low level jet!). Broad 988mb sfc low with a dryline shaping up mostly straight north south. Dews up to near 70 very close to the sfc convergence along it. The only negative I'm seeing are the prog'd storm speeds. 50-60mph!

I'm guessing I'll wind up in Salina tonight, and chase not far from there tomorrow. Probably best to just find a good e-w highway and catch them as they go ne.