09/06/07 FCST: SD / NE / KS / IA

[Rocky Rascovich]

Could be an interesting day unfold across parts of the central plains after about 21Z Thursday. Surface cyclone progged by both the GFS and NAM to deepen to aprox. 999mb (Nam has it at 996!) by 0Z 9/7 across west central KS. based on the 06Z run. All the ingredients will be there for what may be a severe weather outbreak except that the cap may be the spoiler. temps at the 700mb of near 15C is a possibility, this may preclude any meaningful convection from initiating ontil at least 0Z for my target area which is roughly east of a line from YKN to HSI east toward DSM late in the period. By that time, increasing vertical velocities from the encroaching shortwave should overcome the cap.

Everything else looks good with decent deep layer shear, a fair amount of surface moisture being advected north, dews will be close to 70, if not low 70's by 0Z. As of now, I think a broken line of cells will form ahead of the cold front/dry line expected to march east across the area. I'm anticipating that some of these cells if they can stay discrete enough may have a brief period of time that a tornado risk is possible but the main emphasis will be damaging straight line winds of up to 70mph, hail up to 2" in diameter will be the main threats. Because of the capping, storms probably won't initiate ontil close to 0Z but may be a little earlier up around the north sections of my outlook area where 700mb. temps are a little cooler. Best chances based on the last couple of runs may be the LNK to OMA area which has close to the best of all ingredients for some severe weather.

I was leaving for MSP Friday as I've had tickets for a Rush concert for months now

I'll be monitoring the models up through tonight to finally decide if I should leave a day earlier for some chasing.

Rocky&family

 

[Fritz Kruse]

Interesting Day for Nebraska

Strong shear and high instability usually spells trouble. Dews >70, SubT Jet nose, Low Lvl Jet, near 50kts at mid levels crossing over instability axis with greater than 3000 J/kg. Cap should hold until late afternoon, early evening then all heck breaks out. How far south into KS is the question and could unzip all the way down toward Dodge City in the late evening? Would not be suprised to see a Mod Risk or greater for Thursday, with a few significant tornados possible.

 

[Brian Stertz]

To chase or not to chase

Looks like the wave may be a tad late if the 18z MesoEta plays out, but should get things going by early evening in the area between North Platte-Broken Bow-Holdredge-McCook NE. The LCL's do look most favorable for tornadoes along and north of the I-80 corridor. Deep layer shear improves by the evening and nighttime hours with 0-6km shear at/above 50 kts. forecasted, so would expect the greatest risk for tornadoes at/after sunset. The 700mb temps are still pretty warm through the afternoon and early evening hours. I would still expect there to be supercells (fairly high based though) to break out across SW Nebraska into SW Kansas. Most of these should be damaging hail producers...as forecast LCLs may be a little hostile for tornado sustainment. Looks like an active day nonetheless. Tough decision to chase or not. Looking at the GFS, I probably will wait for bigger things later this month to chase. Best of luck to those venturing out on the chase trail tomorrow.

Go get 'em tomorrow Mike H., Dustin, and Sean & Katie !!

 

[Mike Hollingshead]

If I had to pick a target tonight and go to it tomorrow, I think I'd be picking around McCook or just east. Should be just north of the hot low and some drying in nw KS, and right under the coupled upper jet nosing in there. Would think it'd be the best area(closer to the good upper flow) to fire a storm without it having to be right on the cold front. NMM WRF precip thing likes it as well, firing a storm near there at 6pm and continuing it for a while. My other thought was Thedford, but I think I'm slipping away from that for a futher south option. Course it'll all change by then, but probably not a lot.

And yeah, the low level flow sucks that far west(according to the nam). Will take the upper support over the low level flow further east. Guessing both areas get storms. Both east and west already scare me as I'm sure I'll be at the wrong one.

 

[Rocky Rascovich]

Heading out the door momentarily. Target area as of now is GRI. Should get there by 23Z, maybe earlier. By then, scattered convection should be initiating to my west. Best combo of shear, theta E advection should be around the aforementioned area, WRF still has best of these features just to the east and northeast toward OMA. I suspect that the activity won't get good there ontil after dark. Could be quite a squall line event by then with some loops and bows within.

I still think the cap will be an issue, especially the further south you go below I-80, vertical velocities from the shortwave should compensate for that by early evening. Also, I've noticed that both the GFS and NAM have raised minimum pressures with this surface cyclone to at least 1002mb. by late thisevening. Still, I'm expecting MAYBE a tornado or two, primary threats as discussed in my last post will be straight line wind and hail. Hopefully I'll at least get some good storm structure and some lightning.. a Sept. tornado? that will be a first... and a lucky one at that. Now that will be one heck of a way to start my long weekend as I head to MSP for the Rush show!

 

[Dustin Wilcox]

I think I have to agree with the latest 18Z RUC, if chasing I would be keeping my fingers crossed on storms forming and coming out of the area around Salina North to the NE boarder, that region should be prime for Supercells by 22-0Z its on the nose of a 35-40kt LLJ and it appears the midlevel wave will arrive just in time for some pre-dusk action, the area is currently experiencing sunshine and instibility should be more then suffice, warm midlevels should keep it pretty capped down there but the wave has significantly cooler temps associated with it, if only that wave were just a tad quicker. I had a tough choice today, I am pretty much golden to chase anyday except Thursday as I have a night class, I am always willing to miss class to chase but missing the quiz tonight would set me back in my most difficult class, god I can't believe I am actually gonna go to class!!!

 

[Dustin Wilcox]

Appears new towers have blown up just North of Salina or East of Concordia, they went up pretty quickly, hopefully they can fight any remaining cap and sustain themselves as they push East in to >CAPE, and lower LCL's.