4/5/10 FCST: NE,KS,OK,IA,MO

[Verne Carlson]

south-southwesterlies bumping up against southerlies doesn't exactly scream fantastic surface convergence. If the surface winds ahead of the dryline were a little more southeasterly, my hopes for something popping there would be a little higher.

The 12z NAM has the dryline backing west through Kansas from 0 - 6z. Something is moving it west. Has to be winds from the southeast. I am 50/50 on going to Kansas at the moment. Hopefully a few more model runs will make things clearer. I don't have to pull the trigger until the early AM.

 

[Connor McCrorey]

I never put too much faith in the NAM's Composite Reflectivity, but it is showing an isolated cell SW of Pratt at 0z tomorrow. I agree that the cap doesn't look that strong, and I think we could see a storm go up in KS. As Verne pointed out, the dryline is moving west in the afternoon. I don't like that, but it wouldn't be the first time a monster tornadic supercell formed along a retreating dryline!

 

[Dean Baron]

Looks like the GFS and WRF are finally in some agreement. While neither erode CINH completely by 00z, both show a large area of significantly weakened inhibition across southeast Nebraska and southwest IA. At this point my target is somewhere just across the river from Nebraska City, NE...maybe a tad farther north. Even if the models completely change overnight, it was nice to see some agreement between them finally.

 

[Greg Blumberg]

Ouch. What a hit to the setup. That thin corridor of CAPE is back along with no line of eroded CINH. I really hope that 18z NAM run was just the typical 18z model run being screwy.

I wanted to add this...the 12z WRF run by the University of Oklahoma's HOOT site has a line of precip breaking out along W OK to N OK between 0z and 3z Tuesday. Not sure if this has been mentioned.

http://hoot.metr.ou.edu/models/wrf/surf/precip

 

[David Wolfson]

The 24hr RUC I'm looking at (for 17Z tomorrow) is painting a warm front and what I'd term advective cloud crap in southeast KS. This looks to be why the models are having trouble in figuring out if there's convection later. The front moves north, winds back in response to deepening to the west in the afternoon, and south-central KS starts to clear out. The question as I see it is whether this happens soon enough that surface temps can get to 28C or so. The synthetic soundings I'm looking at in south-central KS don't show much of a 850-700 cap in the traditional sense, but rather a surface-850 inversion.

So if I were there (wish I could be!), I'd be staying in Pratt, KS, tonight. With this picture tomorrow i'd be watching surface obs and cloud cover and want to be just east of the dryline and northeast of a nose of low-80s surface temps. Then wait for one of the many short wave impulses rippling overhead to set something off. FWIW.

 

[Greg McLaughlin]

The 12z NAM has the dryline backing west through Kansas from 0 - 6z. Something is moving it west. Has to be winds from the southeast. I am 50/50 on going to Kansas at the moment. Hopefully a few more model runs will make things clearer. I don't have to pull the trigger until the early AM.

It may be in response to the approaching upper low.

 

[Mike Smith]

The 00Z NAM is giving contradictory signals for central KS. At 21Z the model shows a near-perfect tornado situation from Minneapolis to about Kingman. Two thousand jewels of CAPE, good EHI's, shear, and little CAP.

At 00Z (7pm Monday), there is a strong, unbreakable CAP in place. Normally, I would lean toward the CAP winning out, but the model shows the dryline retreating at that time. It has been my experience that the dryline usually doesn't retreat west (at least that early in the evening) under a strengthening CAP.

If the cap is broken, there will be wicked thunderstorms in the central third of Kansas tomorrow.

 

[Verne Carlson]

I think the DL will fire from Concordia, KS to W OK tomorrow just fine. Tonight it fired in W OK and we currently have two nice sups with TVS markers and almost 4" hail. Compare this to the 0hr run of the current 0z NAM. These cells fired in less cape, weaker 500h flow and a trough that is even further west. The NAM shows no cells on the composite radar - yet look what has fired up tonight.

 

[Ryan McGinnis]

Salina's sounding at 21Z sure doesn't look too shabby to me. The NAM keeps wanting to put a hole in the cap in this area, too; it's also giving a precip signal in the simulated reflectivity.

 

[Greg McLaughlin]

I think the DL will fire from Concordia, KS to W OK tomorrow just fine. Tonight it fired in W OK and we currently have two nice sups with TVS markers and almost 4" hail. Compare this to the 0hr run of the current 0z NAM. These cells fired in less cape, weaker 500h flow and a trough that is even further west. The NAM shows no cells on the composite radar - yet look what has fired up tonight.

Sorry to play devil's advocate, but today we actually had surface convergence along the cold front, cooler 850 temps and the influence of a jet streak sweeping out of New Mexico into the southern Plains early this evening.

Tomorrow the NAM shows little if any convergence along the dryline, much warmer 850 temps, and no discernible mid-level impulse. I'm not saying its not going to happen, because you are right, the NAM along with the RUC and the GFS bombed the precip forecast. The NAM also underforecast the available potential instability in Oklahoma today by nearly 1000J/kg.

 

[Ryan McGinnis]

Also, am I nuts or is there a rather prominent shortwave rocking west between 18Z and 0Z? Right along the dryline, at that. Seems to be developing a meso low over York, NE at 0Z, too. Caveat: I might be reading things incorrectly; I definitely have a lot to learn about forecasting.

 

[Greg Blumberg]

I'm looking at the 0z analysis on the 500 mb and 850 mb charts and I'm seeing a semi-consistent pattern of shortwaves being churned out out of the main trough. If this pattern can keep up, the dryline may light up tomorrow.

Additionally, Oklahoma may also light up, considering a potential outflow boundary from the convection currently going on. We'll see if this exists as a mesoscale feature tomorrow.

 

[Skip Talbot]

Check out that hole in the cap in NW MO into SW IA. I've settled on this area for my target tomorrow. Although both the dryline and warm front show beautiful shear and instability combinations, I believe the warm front will have the best chance for daytime initiation tomorrow. The 0z NAM Is even breaking out some precip which is nice chance from earlier runs.

 

[Darrin Rasberry]

Looks like the GFS and NAM are in reasonable agreement on this setup. Noticed the mesolow developed by the NAM as well; the GFS is close enough to that sort of setup for government work, although it puts precip over SC-SE IA instead. We'll be hanging out for the NAM's possibility, but keeping an eye on the eastern play as well. As for now, our target remains unchanged at Lamoni, perhaps a little west toward Shenandoah.

 

[Dan Dawson]

Due to work commitments in the morning and early afternoon, and the fact that I have to leave early Tuesday morning to go to Albany, I will likely not be able to make the trek up to KS for this one. However, I am a little encouraged by the SREF showing some members breaking out precipitation in SW to C OK tomorrow along the dryline, even though the CAP appears to be stronger here than further north. As others have noted, the lack of a distinct forcing mechanism along the dryline is the biggest con tomorrow. I think the cap is likely to erode at least in places along the dryline, but will we get sustained lift to initiate storms (the models have some lift approaching the dryline after 0Z, but it appears to be too little too late)? I note that none of the hi-res WRF runs that I've looked at initiate any storms in KS or OK tomorrow, which is a bad sign in my experience. However, if storms do form, the forecast soundings look delicious, with pronounced low-level veering and straight-line shear in the mid-levels pretty much everywhere in the warm sector, with plenty of juice and instability. Thus, I'll re-evaluate in the morning and keep a close eye on the dryline tomorrow.