3/21/2007 FCST: TX / OK / KS / NE / IA

[afischer]

With the EML, there is a significant cap which the NAM magically eliminates around 5 PM local time. I say magically, but it appears that it is actually bringing the shortwave through, a shift in wind, additional lift, and this is tending to erase the cap. However, I feel that much of this is convective contamination... contamination which may not happen at all if convective initiation is not reached. Stupid feedbacks!

Strongly agree. Isn't the NAM wonderful?

Haven't looked as closely at NE, but I'm still holding out some hope for possible high-based supercells along the dryline in KS. We'll need the stratus to erode ahead of the dryline to get really strong heating/mixing in order to remove a substantial cap. Coverage would be spotty at best. I'd definitely settle for a nicely structured supercell but that even seems a stretch at this point. Will know more in the morning.

 

[Brandon Sullivan]

Two items of note.. I think capping is overdone by the models.. And think it should be able to be overcome.. Also, i think the main activity is going to be confined southern and central IA, Northwest MO, Southeast NE, and Northeast KS.. This is matched very well by the SPC SWODY2.. This may not be the best area of CAPE, but it should be the best area for initiation, most likely the least capped, or the most likely to overcome the CAP. Moisture should be in good supply, and shear should organize any activity.. I'm thinking somewhere in south central IA, like Osceola, or Atlantic.. I want to see things tomorrow before I set sail though

 

[Craig Maire II]

I have changed my mind and after 4 hours of non-stop driving am sitting at a hotel along I-80 in Lincoln Nebraska . I have decided to stick my neck out and see what happens!

 

[Bill Schintler]

Chase target for Wednesday, March 21

Chase target:
Fairbury, NE (roughly 50 mi SSW of Lincoln).

Timing:
Storm initiation 5 PM CDT, with storms reaching severe limits between 6 and 7 PM.

Storm mode:
Isolated supercells along with a risk of short-lived tornadoes between 6 and 8 PM, after which storms should transition into a multicell complex while expanding and moving east and northeast into IA, KS, and MO.

Synopsis:
00Z UA analysis indicated deepening trough over the WRN CONUS with an increasingly SWRLY split-flow pattern to the east of this feature. Two disturbances were noted in the SRN branch, the first of which was lifting into SWRN KS, while an upstream 65kt H5 speed max was rounding the main trough base over SRN CA. An axis of H85 moisture advection has become established over the CNTRL and SRN Plains, however H85 dewpoints in excess of 10C remained well S of the H85 WF located near KS City. At the surface, a WF extended EWRD from an organizing elongated area of low pressure over the ERN Rockies, across KS and MO along a line parallel to and roughly 50mi S of I-70. In the cool sector, an area of mainly rain was located in MO and SERN IA, this apparently in response to a potent 40kt H7 shortwave over MO along with isentropic up glide along the 295K – 300K surfaces.

Discussion:
Locations were both instability and shear will be adequate for rotating, surface-based updrafts will be limited, except for along and just N the SFC WF at the intersection of an advancing DL where a narrow axis of instability with SBCAPE’s to 1500J/kG will develop by late afternoon. Examination of forecast soundings indicates an EML with a strong inversion between 850mb and 750mb along with nearly dry-adiabatic lapse rates from 700mb to 500mb and a 150mb-deep moist layer with SFC dewpoints of 60-65F. The NAM is more bullish than the GFS and NGM with laps rates and attendant instability, and is too optimistic.

SRLY SFC flow will exist beneath a veering 30kt LLJ, which will contribute towards (SFC-3km) SRHs to locally 200m2/s2. Deep layer sheer will increase to 40kts as a compact H5 speed max located between the SRN and NRN branches approaches. An H8 ST deck will erode from W to E during the afternoon hours, allowing for a few hours of insolation. Inhibition will be strong, however convection should initiate as mid-level temp cool during the late afternoon hours and the DL surges EWRD onto NCNTRL NEB.

- bill

 

[Verne Carlson]

The 12Z WRF/ETA model run is out and my target from yesterday 'remains' to the north of Russel, KS. If I had to pick a town, I'd say somewhere near Concordia, KS. The road networks in this area are good in case we have to go north. Everything is set to get up at 5:00am tomorrow, pick up Michael in Lafayette and be on the road by 6:00am. Concordia is 7 hours away so that should put is at the target area at 2:00pm CDT with a couple gas stops along the way. Tony, Jon, Tom and Jenn are meeting at the Airport P&R at 6:30am on I-70 so that will put us all on the road at about the same time.

Only fly in the ointment that I can see in the latest model run is the 500mb winds are a little lighter than previous runs, hopefully we'll see those kick in stronger than progged.

Cap could be an issue as the 'significant' cap line runs through Salina, KS and points south so we're pretty close to it. 6-7 C at 700Mb is the rule here according to Jon Davies site: http://members.cox.net/jondavies1/700mbTcap/700mbTcapguide.gif

Excited to be out again on the first full day of spring and almost one full month after our successful tornado intercept on Feb 23, in McLean, TX

 

[Brian Stertz]

Tomorrow's chase plans

Still favoring the good theta ridge poke and weaker cap up towards the Lincoln NE area....will target the chase area between Fairbury and Lincoln as my starting pt. Rich & Ryan Thies and myself will be hitting the road sometime around 9am from KC on the way to that area...probably will hold in the Wilber-Western NE area and likely meet up with Dustin Wilcox and Katie McMullen there.

http://grib2.wxcaster.com/wxcaster4/CENTRAL_ETA212_ATMOS_SIGSVR_24HR.gif

 

[Skip Talbot]

0Z WRF has a cap hole sitting over Des Moines, IA at 0z with 1500 JKg and vertical velocities spiking from 850-500 levels. Des Moines is well into the warm sector so if something goes up there it won't be quickly undercut by the cold front. However, surface winds are mediocre and out of the southwest and 1km SRH is lacking (as it is everywhere though). 6km speed shear in the mid 30's and 3km SRH of 200-300 could definitely support supercells. Folks in Iowa might want to keep their minds open to this area instead of exclusively focusing on NE and KS. I'm going to make a final call on this chase in the morning.

 

[CraigFisher]

Wow, Tuesday my initial target was going to be the area of Superior - Red Cloud , Ne to Concordia, KS. After looking at tonights model runs it looks like I won't move far from home. Cheap chase.
Getting off of work at 2 pm, will probally initially set at Fairbury, Ne. HWY 15 should give me good mobility for north/south and 136 for east/west.
Hope everyone has a good chase, and be safe.

 

[Mikey Gribble]

I am pretty sure I will be sitting this one out. If I was going to get out I would chase north-central Kansas by the triple point. I don't know what to think about the cap at this point. I am leaning towards thinking you will get a storm coming off the triple point, but the dryline will stay quiet. I am half asleep though and I haven't spent much time working on my forecasting, so I'm not real confident ATT, but I probably won't look at data again until this morning's soundings come out so I figure I better throw my 2 cents in now. For some reason the main sites I use for forecasting aren't working right now. Assuming a storm does fire up there, I think the tornado potential is minimal. I wouldn't be suprised to see a 2% tornado probability up there later on today. I would rather bide my time than chase a mediocre at best setup for tornadoes, especially with what the GFS is showing next week. Good luck to everybody who heads out today.

 

[Brandon Sullivan]

I will be heading out.. Not sure where yet. Thinking somewhere in SW IA.. But don't want to waste all my funds, seeing that this weekend looks interesting, and I would have much more time to chase then..

 

[Jason Boggs]

I'm going to stay close to home on this event. Dryline will set up in the eastern tx panhandle with some pretty good instability. CAPE should be in excess of 2000 and the daytime temps will be in the upper 70's. Ofcourse the CAP will be a major pain for any convection to get through but I will probably just sit in Shamrock at the McDonalds (WIFI ACCESS) and wait. If this is believable, at least one storm will get through the cap after dark in the panhandle!

 

[Michael O'Keeffe]

I'm targeting the Concordia-Hebron corridor. I like the 59F dewpoints at 8am! This is where instability is highest and IMO is where the most unstable air is. Mesoanalysis showed the SigTor paramanter at 1 already. That's not off the charts but pretty high for this time of day. The new SWODY has the tornado threat at 5%. That's better than nothing. I see the possibilty of tornadoes greatest where discrete storms can fire.

 

[Jason A.C. Brock]

I will also be playing the dryline. Storm up North in Kansas and Nebraska look like a good bet but I am not sure they will be worth taking the chance on driving 8 hours. I will be headed out towards Childress area to be ready to launch out into the Panhandle in the event a storm can break the cap. Just a couple hour drive up 287 is alot ore convenient. Ill also save at least some gas money for storm chances closer to the weekend. Thats for another thread however.
Id like to see the dewpoints rise in SW OKlahoma out towards Childress and even here in Wichita Falls at least a few degrees. That is a good possibility tho with winds here expected to be southerly at 30-35 at times pulling some of the little better stuff up from the North Texas area around DFW and along I-20.
Storm may not fire till late afternoon if they do at all.....maybe 5-7pm? If they fire closer to sunset they may not be able to fully mature after they lose some of the heating. Then again.....I may be watching some agitated CU at best. I have to at least give it a shot tho. AH Childress....Wichita Falls Version of Shamrock to Norman.
Ill look at data at the Shell station when I get there and decide to either stay put or move to a better spot. I doubt ill head out till 1pm at the latest.
Good luck to those up North. Perhaps a nice cell will get isolated before the front destroys it.

 

[Tony Laubach]

An emotional forecasting roller-coaster for me over the last 36 hours and unfortunately last night's 'LESS THAN 2%' sucked the life out of all of us! We debated long and hard on the phone well after midnight last night deciding what to do and elected that between the eastward extent of the target and CAP issues, which we had our doubts about, that it was probably not worth getting up at 6am to haul out there.

So comes the morning and a new graphic has the few of us left behind kicking themselves. Verne and Michael Carlson can fortunately take an easy traffic-free way around Denver and are hauling out east as we speak. Me, living on the west side of town, would have to fight the morning traffic to even have a chance to get out and would likely be looking at a 90 minute drive just to get out. I'm home, and hopefully by 6pm this evening, won't be kicking myself for the last flip-flop.

Good parameters are coming together in northern Kansas/Southern Nebraska. Good dews are setting up already across the region as a surface low in extreme northwest Kansas is aiding to back winds. As the day progresses, this will move eastward into the better air and give excellent shear profiles across northern Kansas/southern Nebraska.

I have no idea what to expect from today... the downward trend of the forecast over the last 36 hours really sucked dry the enthusiasm for today, so getting up this morning to this has me sick to my stomach! LOL Hopefully Verne and Michael will do well for their chance today, so we'll see. Best of luck to them!

 

[bbarjenbruch]

For some of you guys who live farther from the SPC target area, I don't blame you for waiting on the weekend event. Here in Lincoln, we have the low stratus deck I was worried about. Much to my excitement though, it's 61 degrees at 9 AM anyway! Add that to the 59-60 F dewpoints, and we might be in business later today. I'm still worried about the possibility of the cap not breaking enough for discrete storm developement... the 06Z GFS doesn't even erode it completely. The RUC on the other hand is looking pretty good, and actually holds 150 m2/s2 0-1 helicity in SE Nebraska at 00Z. If nothing else, that's pretty exciting. Good luck to the chasers!