05/18/05 FCST: KS/OK/NE/IA/MO

[Ben Prusia]

Overly, I am not too confident in this day producing, but here goes:

12Z NAM showing a dryline moving eastward into eastern Kansas and central and eastern Oklahoma by 0Z Thursday. Ahead of the dryline, there is a pocket of 65+ degree dewpoints from north central Oklahoma to south central Iowa. However, GFS model is showing more extensive 70+ degree dewpoints for areas Kansas City, southwestward. I am questioning either model on their availability of that much moisture being available. Instability will be modest, with SBCAPE values running above 2000 J/Kg. SRH will not be our best friend during the day, but 100-150 m2/s2 with some pockets of higher could make for a spinup or two. One thing that could be a killer, although, is the intense lack of shear as 850mb winds are blowing SW at 25-30 knots, while values higher at the 500mb level are blowing W at 30 knots. Looks like a marginal setup at best, with a good chance for some soaking rains and large hail, but looks like there could be a tornado if any cell got their act together. Hopefully if the GFS pans out and surface temperatures remain in the lower to mid 70's near Kansas City, we could get some surface based action up here with the forecasted lower LCL's.

Graphic for this forecast can be found on the "My Chase Forecasts" link below.

EDIT: Topic changed to include Nebraska, Iowa, and Missouri.

 

[Jeff Snyder]

Originally posted by Chris Foltz
Looking at the 00Z models, it appears severe weather will be possible tomorrow. My focus right now would be on SE KS where the best combination of shear and moisture exists. Decent 500mb winds of 30-35 kts with slight divergent flow that will aid in lift. Current target would be somewhere in the vicinity of Parsons, KS. Waiting for later model runs to see if this verifies. Moisture might be less of a concern than it is today with dewpoints near 65 per both NAM and GFS. GFS is actually showing near 70 dewpoints in SE KS but don't believe this will play out as I can't see where this moisture would be coming from. Any other thoughts?
_________________
Chris Foltz
Mizzou Storm Chase Team

 

[Scott Lincoln]

I'm not sure that I agree with the target area of this topic at all.
I dont think that Kansas and Oklahoma will be the target for many tornadoes tomorrow.

Based on shear and LCLs, I think southern Iowa and northern Missouri have the best threat for tornadoes... but only if enough instability can be present.
Based on two different models I've seen the LCLs in central Iowa as 750ft or <400m.
The shear also appears to be maximized in northern Missouri and eastern Iowa.
I can see there being a possibility of supercells in Kansas, but the LCLs will be much higher and helicity will likely be lower. Our best bet would be to hope for more instability in Missouri and Iowa than the models are projecting, so storms can take advantage of the low LCLs and somewhat decent shear.

 

[Gabe Garfield]

I'm not sure that I agree with the target area of this topic at all.
I dont think that Kansas and Oklahoma will be the target for many tornadoes tomorrow.

I agree. Storms will occur in Oklahoma/Kansas, but I'm not so sure that the threat of tornadoes is as good as northern Missouri, based on the 12Z ETA. Flow aloft is sufficient (almost 40 kts from the west at 500 mb) and the low-level jet is maximized in this region. In addition to this, the instability will be just as good with CAPEs approaching 3000 j/kg in some areas.

Even so, tomorrow remains somewhat marginal.

Gabe

 

[Jeff Snyder]

A rather odd pattern for severe storms tomorrow in the KS/OK area. From a numbers standpoint, things don't actually look too bad. While absolute flow in the mid-upper levels is not particularly strong, there is very strong direction shear through the troposphere -- from SSE winds at the surface, to NW winds at 250mb. This, at least per the 0z NAM, yield ~40kts 0-6km deep-layer shear, which, when combined with 3000-3500 MLCAPE (courtesy of 65-73 Tds), will likely prove sufficient for some decent supercells (storm mode aside). Given that the deep-layer shear vector is from the NW, a NE-SW oriented front will result in a near-normal orientation of the shear vector and intiating boundary, which is often a good sign of discrete activity preference. The better 850mb flow will reside in OK, but 0-3km SRH is progged to be in the 150-200m2/s2 range given a westerly (10-15kt) storm motion. IF we can get a nice right-turner, I think a particular supercell could see more like 250-300 m2/s2 0-3km SRH. Temps should be in the 80s, but with the Tds near or MAYBE exceeding 70F, LCLs should be quite do-able.

EDIT: Not sure the NAM >70 Tds will verify in KS/OK tomorrow. I don't see >70 Tds anywhere on the TX Gulf coast... I do think upper-60s are quite possible, however.

 

[Mike Johnston]

Looks like we have the potential for a severe setup Wednesday from NW MO, through E and S Central KS, to Central OK. Upper and mid-level flows, while not off the charts, are forecast to be supportive. HWO's in the KC/Pleasant Hill forecast area are raising the possibilities, but put in a big hedge re: insolation & instability being contingent on sky cover clearing in the wake of expected overnight convection (although such convection appears marginal as of this writing.) Of particular note are forecast low LCL's and NW flow at 200mb which shows a fair degree of diffluence around NW MO and NE KS. Based on 00z NAM, one can identify a bullseye around the Leavenworth/Atchison area, which has seen its full share of storms move through so far this season.

Although severe parameters look decent to good, focus for initiation at the surface level is a little difficult to pin down at this point. No obvious concentration of surface moisture convergence yet appears on the maps, while tightest dewpoint gradients and tongue of theta-e advection show across central KS and central OK, and outflow boundaries from overnight convection may have a role to play. Forecast surface wind field changes through the day aren't exactly the sharpest picture one would look for. I'm thinking if something isolated is able to develop out in front of the dry line in E Kansas, though, we could see a tornado on Wednesday.

 

[Justin Walker]

Agreed with Jeff...tomorrow is interesting. There will be a lot of directional shear but the speeds are minimal for sup support. However, that said, I think we will see some sups tomorrow on the front. On thing that I like is that NAM is progging 70's Td's across SE KS, I don't see this happening, but upper 60's will keep LCL's lower. LCL's have been high this whole stinkin spring. :x

I really didn't forecast for N of I-70, but If I were chasing, I would probably start out around the Arkansas City, maybe drift east towards Sedan/Independence area. CAPE approaching 3500 J/Kg...I think a couple of weak tornados are not out of the question in this area. Good Luck to all!