05/11/05 FCST: Central/Southern Plains

[Mikey Gribble]

After looking at the 00Z NAM I am not quite as excited as I was before, but it sill looks like a couple of tornadic supercells are likely. The surface low is located in NW Kansas. It might be a hair farther South than it was with the previous run. Dewpoints will be in the 60's with 65 a little further to the East. Near the triple point shear should be >45kts with 2500-3500J/KG CAPE and 500mb winds at 50kts. Weak shear will be a problem for any storms along the dryline South of central Kansas. Lapse rates are forecast to be very steep near the triple point and along the dryline. It looks like HP will be the primary mode tomorrow.
The target area for tomorrow is a no-brainer for me. First of all the NAM doesn't show any precipitation along the dryline except for near the triple point, not that I buy into that though. Second of all, storms that form on the northern portion of the dryline/triple point will be tracking NE into an area of increasingly lower LCL heights and higher helicity plus they will have stronger shear. I am expecting storms to come off of the triple point and right turn once they organize and encounter the better helicity. I will be heading towards Colby where I will fine tune my forecast. For those who are interested, there is a wifi spot on the West side of the road after you get off of 70 in Colby. I only glanced over things and I don't really know what I am talking about so don't put too much stock in my forecast. I will look more closely at things in the morning, but from the glance I took the only problems I see are LCL heights that are a little too high, CAPE that is a little too low, directional shear could be better, and stronger upper level winds would be nice. Bottom line though, what we got will be good enough to get the job done. I will see you all out there tomorrow and good luck.

 

[Andrew Pritchard]

Surprised no one is mentioning Illinois...even the SPC only has 15% prob. This is easily the best set up illinois has seen this year. CAPE progged around 3000-4000 by mid afternoon, with surface temps in the mid 80s...and td's around 65-70. Outflow boundary from overnite mcs and warm front over the central part of the state should serve for intense convective development early afternoon. They should quickly become severe, and likely supercellular with good shear, and helicty values around 300-400. Additionally, any storm that forms near the outflow boundary will be able to interact with it, tapping into enhanced helicity areas, enhancing the tornado threat. Be interesting to see if the SPC is watching this at all...or if we're sneaking in under the radar again with the attention on the plains. Things could change overnite...but attm, it appears Illinois and Indiana should be monitored.

The forecast sounding for Macomb, IL tomorrow afternoon has cape @ 4000, strong SE winds, EHI of 4.2, and supercell pot. of 77%. Now, yes, these are just forecasts, and indicies...but...surprises me to see no one talk about this situation.

 

[Jeff Snyder]

I agree with Michael in the post above this one... For whatever reason, the >65 tds just can't get to the dryline.. .Now, remember that the models tend to lengthen/smooth the gradient, so we may see higher Tds near the DL. Regardless, CAPE should be in the 2000-2500 range, with 0-3km helicity good near the front in northern KS. This looks like the first, and little more like-to-produce, target. While flow in the mid-upper levels is sufficient, the lack of much speed shear results in 0-6km deeplayer shear (per the 0z NAM) that is on the low-end for supercells -- 25-30kts.

Farther south, same story as far as deep-layer shear is concerned. The >65 Tds appear to nudge up against the dryline a little better, and the NAM is picking up on a little stronger low-level shear (helicity) east of the dryline by afternoon and evening across eastern tx ph, far nw ok, and into sw/sc KS. Again, however, the NAM does not break out precip along the dryline until after 0z.

Overall, it still looks like the best bet is up with the sfc low, though I'm not quite as excited as I was before. Regardless, I think the dryline may be a good place for those who don't have time to make it farther north. I don't mind WF chases, but it seems that storms tend to congeal into lines/clusters more quickly than their dryline counterparts. We'll see.

 

[Jim Bishop]

NAM shows convection firing in the early afernoon along the warm front in southern/southeat Nebraska. I think the main show will hold off until later in the afternoon over northwest Kansas/southwest Nebraska on the triple point.

Any supercells that form near the triple point and can room themselves along the warm front will produce several tornadoes. Shoot, any supercells that form near the triple point at all have the potential to produce tornadoes, but they risk crossing the warm front with the 25-35knot northeast storm motion.

 

[Nic Wilson]

Target 1: Concordia, KS

Target 2: Hill City, KS

Deepening 999 mb sfc low will be in place over western KS by 00z with warm front draped between the I-70 corridor and NE border and attendant dryline extending southward into the OK panhandle and the far eastern extents of the TX panhandle. 50-60 kt 500 mb jet max enters northwestern KS during the forecast period, balancing the potent 30-35 kt flow at 850 mb. Helicity will be maximized along the warm front, similar to the storm initiation seen Tuesday. 0-6 km bulk shear of 45 kts will support sustained supercells in an area from areas northward of Sherdian Co. in the west and Ottawa Co. in the east. The dryline exhibits a nice bulge south of the warm front with 65+ Tds available further east from the sfc low.

My favorite target from the 00z run would be Concordia, KS which will be rooted along the warm front with some jaw-dropping NAM forecast sounding parameters: 335 m2/s2 0-3 km SRH, SBCAPE 4500 J/Kg, 3 km EHI 9.6, LCL ~750 m, storm motion 225 ~ 25 kts. Only concerns are CIN of -56 J/Kg...but forcing mechanisms should be in place to break this down late in the day and moisture is very shallow so long-lived tornadoes will be difficult..many small ones like Tuesday will be likely. Hill City and points closer to the sfc low north of I-70 are also enticing, but moisture does not appear to be as ample despite nice low-level shear. Adjustments will be likely after the 12z NAM and RUC come into play in the morning. Looks like we'll be departing OUN around 9:30am for the drive up north. Good luck to everyone heading out tomorrow!

 

[Jeff Snyder]

Well, as usual, the RUC and NAM are at odds. The 0-3km SRH is crap on the RUC, while it's pretty awesome east of the entire dryline on the NAM. With 35-48kt SSE 850mb flow, we'll see awesome low-level shear east of the dryline dryline, more see across KS then OK/TX panhandles. With CAPEs progged to be in the 2500-3000 range, I could certainly see a 15% hatched tornado risk across western/northern KS, and maaaaybe down the dryline farther south. If we lower LCLs / higher moisture, and we had a little stronger upper-level flow, I could see a high risk... well, that's assuming the NAM will verify. RUC breaks precip down in eastern TX panhandle, and along the warm front, while NAM breaks out precip along the entire dryline. I'm planning on heading up to I70, then west. Stop for data... if it appears that NAM is verifying, won't worry about going too far north... If the RUC appears to be doing better, will have to move northward closer to KS/NE border.

 

[Jim Bishop]

I agree to an extend with what Jeff said. The NAM is forecasting the backed 850 winds to remain backed while the RUC shows them veering a bit back towards the south by 00Z. But that shouldn't matter to much for the best area which is still northwest Kansas/southwest Nebraska and east along the Nebraska/Kansas border along the warm front. That area looks amazing for tornadoes no matter which verifies.

I agree there is still good tornado potential further south along the dryline if the NAM verifies given great forecast hodographs. Personally I'd head further north and play that game (if I could chase), but I guess that's a distance preference. Of course there's concern with respect to storms crossing the warm front and becoming elevated/dissipating, but any that turn right and ride the warm front will be tornado machines!

Happy Chasing!

 

[John Sickels]

analysis

Mesoscale analysis as of 11:00 AM shows supercell composite parameters as high as 10 and significant tornado parameter at 1 across portions of northern Kansas. There is also evidence that the cap is weakening. CAPE as high as 3500 in vicinity of Salina.

 

[Anthony Petito]

Originally posted by Jeff Snyder
I could certainly see a 15% hatched tornado risk across western/northern KS, and maaaaybe down the dryline farther south.

Looks like SPC agreed with you in their latest day 1 tornado outlook. They upgraded to a 15% hatched area.

If the RUC appears to be doing better, will have to move northward closer to KS/NE border.

I think this is where I will play today. I'm looking to setup near the NE/KS border, just south of Beatrice. Although, there's still a lot of day left so it will probably change