04/21/05 FCST: Central/Southern Plains

[Ben Prusia]

0Z NAM shows something that I have been wanting to see in a while, 500mb winds! 30-50 knot winds at the 500mb level is expected at 0Z Friday in an area west of US Highway 69 in Kansas. Though CAPE will be lower, expected to be around 3000 J/Kg centered at SE Kansas and LI's of -4, I still expect severe weather to develop. SRH will be higher at the 3km level, 150-200. Dewpoints are expected to be in the 60's, allowing for the development of severe weather. The target area for development would be anywhere in the neighborhood of Topeka southwestward to El Dorado, southward to OKC and maybe Tulsa. SPC has a swath of 25% SVR from east Kansas/west Missouri and northeast Oklahoma/northwest Arkansas.

The graphic for my forecast can be found on the forecast link on my signature.

 

[Marcus Opitz]

I may chase on the night of the 21, but i may wait till things get really going in may. It seems that the Jet stream lately has resembled a July pattern?? I will be driving from Kc to springfield that evening, so maybee I can catch some action on the way, but it is too far out to change plans. Maybee I can actually get some of my moneys worth on that RAZR phone I bought to utilize the many wap weather sites..........

 

[Billy Griffin]

Perhaps Thursday will be the first "really good" chase day for north-central into central Oklahoma. Surface low appears to set up in far NW Oklahoma with associated dryline, cold front and warm front draped through KS into MO - - - classic Triple Point setup. Well, at least that's the graphic that the OUN HWO displays for Thursday's severe weather possibilities.

If things fire, I hope they will hold off initiation until after 4-5 pm.

Good luck to all on Thursday !! :wink:

 

[Mike Johnston]

Prospects for Thursday seem to be holding together very well through the latest runs, especially for eastern tier of KS, western tier of MO, and northeast OK. Key to this scenario is ejection of vort max, finally bringing "real" 500mb level winds of 45 to 55 kt over central/southern plains. Very encouraging setup in the warm sector, with MLCAPE values of 1500 NE KS up to 3000+ NE OK, dewpoints 60 to 65, and nice directional and speed shear ahead of advancing cold front. With theta-e ridge forecast right along KS/MO border on the 00Z run, look for convection to initiate just upstream in mid-afternoon. Really like the steep lapse rates, too - hey 9.5 over Girard, KS has the ring of a target! With a real lifting mechanism finally coming through after 3 days of juicy surface flow, this could be the day.

 

[Anthony Silver]

Yep, things are certainly looking good for Thursday. I'm already making Plans for a chase day. The models look highly favorable. The latest SPC outlook has Central/Eastern KS, and Parts of MO in a slgt risk with a 25 hatched ring, which will likely be upgraded in later outlooks. Im still looking at Topeka southward to Wichita as my target area. Time to take the SWIFT WX and Storm Lab software for a spin.

 

[Karen Politte]

Strange, when I look at Thursday I see COLD FRONT through almost the entire region (look at the surface on the models). And I don't want to chase Iowa or Missouri......so I'm hosed.

KR

 

[Ben Prusia]

12Z NAM shows a classic triple-point setup for severe weather that will move through east Kansas, southeast Nebraska, and northeast Oklahoma during the day on Thursday. Upper level winds of 30-60 knots, with a 0Z Friday peak of 50-60 knots around Topeka/Lawrence, Kansas will support supercell development along with the chance of tornadoes. Also at 0Z Friday, the NAM model shows the upper level Low Pressure system centered near Omaha, and I believe that best chance for severe weather will be to the immediate east and immediate south of the Low Pressure. Looking at the usual parameters that I always look at, we can see a wide swath of -6 to -8 LI from roughly Omaha, Nebraska, southward to southwest of Dallas, Texas. CAPE can reach around 2000 J/Kg near the Omaha/Nebraska City area with higher instability to the south, with values reach up to 3000-3500 J/Kg between US Highway 69 and US Highway 71 near Fort Scott, Kansas and Joplin, Missouri. NAM model also shows precipitation breaking out near Omaha, southward to the Kansas border, then there is a break, but picks up again south of Lawrence/Ottawa, Kansas areas and continues south and east to Joplin. Best chance for soupy air and higher dewpoints sit along US Highway 69, to the south of the Kansas City Metro Area, but for right now, still choose a target area in extreme southeastern Nebraska/northeastern Kansas/northwestern Missouri. I will not majorly believe what the NAM has been saying for dewpoints because they have been overplaying the dewpoints/CAPE lately.

Omaha HWO has some good wording for tomorrow:

A POTENT UPPER LEVEL STORM SYSTEM WILL MOVE INTO THE AREA ON
THURSDAY. THIS WILL BRING ANOTHER CHANCE OF SEVERE THUNDERSTORMS TO
THE AREA. DUE TO STRONG SHEAR IN THE ATMOSPHERE SOME OF THESE
THUNDERSTORMS MAY BE SUPERCELLS. LARGE HAIL...STRONG DAMAGING
THUNDERSTORMS WINDS...AND ISOLATED TORNADOES WILL BE POSSIBLE.

Graphic for this forecast can be found on the forecast link on my signature.

 

[Mike Johnston]

Karen, the front may be the lifting mechanism we need. Position of front moving through in relation to diurnal cycle on Thursday will probably be the key. Latest runs have it a little further east by 00z, which I don't like, but still good possibilities for convection NE OK up along KS/MO border in the late afternoon in the warm sector.

 

[Ryan McGinnis]

Thursday is beginning to look very exciting for my area, southeast Nebraska. Triple point floating right on top of us @ 18Z, with GFS & NAM in fairly close agreement that there will be ample moisture and instability and a great LL jet. And, for a change, rip-roaring 500mb winds. NAM even has divergant 250mb winds over E Nebraska by 18Z. I will be shocked as a radio tower in a thunderstorm if the SPC doesn't upgrade E Kansas, SE Nebraska, W Missouri, and maybe a sliver of SW Iowa to moderate. This looks to me like the best chase day so far this year for the CP.

--

Disclaimer: poster is very new to forecasting.

 

[Justin Walker]

The models have really been struggling with this system. ETA appears a little more favorable for discrete cells going up (better directional shear) as compared to the GFS whose analysis shows more of a unidirection pattern. We will have to wait for later runs to get a better idea and morning soundings.
As for moisture, mid 60's in SE Oklahoma, I don't think models are over-doing moisture return. Upper level winds are finally more favorable for SC's but my concern for tomorrow is the weak cap. Temp's of -14 or less across SE Kansas and NE Oklahoma worry me. With all the convergence and lift associated with the low and dryline, i'm affraid the storms will go crazy HP style!! I guess we'll wait and see.

 

[Mikel Shively]

well....Finally get a close to home chase.

Target Area: Bethany, MO

Currently looking for some Supercells to develop in the 3:00 time frame....However, if there are clouds in the morning, all bets are off, may not get enough instability for TOR's but still should be enough for a decent hail event.

 

[Ben Prusia]

0Z NAM shows the classic triple-point setup in place for the development of severe weather during the day on Thursday. The upper level low pressure system is progged at 1006mb, and is centered near Kansas City (about 100-150 miles further south than the 12Z run earlier today) at 0Z Friday. My current thinking is that the best chance for severe weather will be east and northeast of the Low Pressure, targetting along Interstate 35 and also the Kansas City Metropolitan Area. At 18Z Thursday, LI of -8 will exist in east Central Kansas, predominately along US Highway 77. CAPE in this area will be around 2000 J/Kg and will be supportive of supercells to develop east of this area. With dewpoints of 65-70 degrees, expect storms to develop in east central Kansas and move northeastward to Emporia, Topeka, and Kansas City. The 0Z NAM also shows precipitation break out along the US Highway 69 corridor. Upper level winds will not be a problem in the entire east Kansas quadrant, with 500mb wind speeds at 40-50 knots. I expect, at the moment, to see numerous tornadoes along with many reports of golf ball size or bigger in a wide swath from Omaha, Nebraska, through Kansas City/Topeka, all the way to about Tulsa/Oklahoma City. Will wait for tomorrow when the RUC model takes over for further analysis.

As of this writing, SPC has eastern Kansas and most of west Missouri in a SLIGHT risk, with a 25% chance with hatching for a chance of significant severe weather. I expect that this area will be upgraded to MODERATE risk during the day tomorrow.

Graphic for this forecast can be found on the "Forecast" link on my signature.

 

[John Sickels]

target

Target area for tomorrow:

My house in Lawrence, KS. I don't see much reason to trek out. If the sun clears the clouds away early enough there should be a good show here.

Hopefully not TOO good. Tornadoes in populated areas are not my idea of a good show.

 

[Jeff Snyder]

I'm probably going to head out towards Okemah late-morning time frame...

This evening's NAM runs shows a couple of interesting development from previous runs. First of all, the 500mb jet max in the central plains is more broad, resulting in stronger 500mb flow down into OK. Second, and more important in my eyes, is that the NAM shows winds not veering nearly as much across east-central Oklahoma, with a minor surface low perhaps near Okemah by afternoon. With less-veered flow (not quite willing to call it 'backed', though both are relative terms I supppose), low-level shear should be stronger, as NAM is indicating a bullseye of 250-300 m2/s2 0-3km SRHelicity by 0z centered around the OK/northwestern AR border area. This is slightly suspicious, given the noisy-looking SLP field at 18z in the general area (and slightly to the northwest). Regardless, if winds can remain out of the south (though an easterly component would certainly be appreciated), I think the low-level shear may be strong enough for the 3000-3750 j/kg SBCAPE to work with... The 35-40kts 0-6km shear will certainly be a welcomed change from the past few days down in the southern plains...

With all that said, a look at morning visible satellite will certainly be necessary. Stratus has developed in this area the past several nights east of the dryline, and I fear the same will happen overnight. Assuming we can mix the low-level clouds out to allow for insolation and subsequent destabilization, I think we could see a couple of tornadoes in eastern OK tomorrow. I'm also interested to see if any outflow boundary from current convection in southwester/southcentral can remain discernable through tomorrow morning. FDR radar was showing a nice OFB extending from the convection earlier, though the LLJ tonight may mix that out...

 

[John Sickels]

models

At this point I don't trust any of the models except in the most general way. . .there will be severe weather somewhere along an Omaha/Topeka/Wichita/OKCity axis tomorrow. Aside from that, we don't know how early tonight's convection will clear out in the morning. We could be socked in in Kansas all day Thursday like Nebraska was on Wednesday, ruining an otherwise good setup. Or we could have a major severe weather event, maybe even a large outbreak, if the clouds clear early and there is more shear than forecast currently. We could even see a high risk somewhere tomorrow, probably a narrow axis wherever best conditions set up.