05/10/05: TALK: NE/IA/IL

[Scott Olson]

With 60 Td's already creeping into Southern Nebraska now I don't think the NAM is that far off. I'll most likely be playing around Sioux City or within 20-30 miles south of there.

EDIT: 12Z NAM is forecasting LCL's between 1400-1600m in Eastern NE. Still pretty high but better than last nights run. RUC13 also now starting to pickup on some convection.
-Scott.

 

[Mike Johnston]

Wow - RUC is showing a much more rapid W to E progression of dry air at the surface over the course of the day than the 12z NAM. RUC also has surface low in E CO deepening to 991mb by 00z. Probably due to this difference in progression during the diurnal cycle, Tds and CAPE values peak much higher on the NAM. NAM also shows lapse rates reaching absolutely unstable conditions of 10 over a very broad area of southern and central plains. Good news on both models is improved upper air support at 500mb. Will be interesting to see how the next SPC outlook addresses the development today... as for me, I am just going to sit tight here in KC area as long as possible. Before pulling out the gas credit card, I figure the more last minute knowledge, the better today.

 

[Justin Walker]

I think today has the chance to become interesting. NAM is really calling for instability, the RUC is having a brainfart. :wink: Upper level will finally support sups along the warm front today. Low level helicity will be the strongest in the NE area. If I were chasing today, I would play the Warm front. OU finals week....gotta love it!!! :cry:

 

[Bill Schintler]

RE: Chase target for May 10

Target:
Denison, IA (about 50 mi NE of Omaha).

Timing:
Storm initiation 6 PM CDT.

Storm intensity:
Supercells early in storm evolution, with large hail the primary threat. There is also a small chance for tornadoes.

Discussion:
Late this afternoon and overnight, a warm front and strong LLJ will be the focus for severe weather and very heavy rainfall. 14Z SFC analysis showed elevated convection along a 9V9-LLM line, as well as extensive ST N of an ONL-YKN-ALO line. SFC streamline analysis failed to show any well defined boundaries other then some convergence along an YKN to SHL line, likely a result of weak outflow from the precipitation to the north. This boundary should strengthen today as a result of differential heating and surface winds in NE and IA switching around to the S. “Warm sector†dewpoints were only around 50 in NE and low- to mid-50’s in IA.

Latest RUC and NAM guidance agree on position and evolution of the WF, SFC conditions, and QPF location and timing. Later tonight, textbook MCS conditions – ridging in the upper levels, along with a 355K SFC theta-E ridge and a 60kt LLJ nosing into WRN/CNTRL IA. Severe storms will be likely, especially early in storm evolution, where MLCAPE’s will reach 2000J/kG and 0-3km SRH’s will locally exceed 500m^2/s^2. A concern is high LCL’s where T/Td spreads will approach 30F in the warm sector, however areas immediately to the north of the WF should see LCL’s in the 1200m AGL.

- bill

 

[Mike Hollingshead]

Looking at satellite I don't think you'll have to go north of North Platte. Which is always good as the roads out there SUCK. That cloud cover is a bit scary out there. I guess I might be getting interested in a line from Curtis to Kearney.

The ruc may be right with the dews. You can see the cu field in KS being scoured out quickly from the west. The last 12z eta and 18z eta were showing a lovely veered 850/900 nosing towards Omaha with drier air behind it. I can see that on the ruc now..and the 12z eta today. Will that matter with the very backed flow along the front I'm not sure but I'm starting to think so. This makes me want to wait right here where the nose of the LLJ will be moving over the warm front(when it starts to try and back a bit and has the eastern edge of dews along a n-s line here with the "bulge"). Between 0z and 6z eta continues to go wild with something in western IA. Moisture convergence really increases here between 4 and 7. Ruc has convection on the boundary here at 7 now too. West nearly always seems like the safer bet for initiation and I'm sure there will be some out there. I guess just a few too many things keep me from leaving this target of eastern NE.

 

[Chris Allington]

think that moisture is going to begin to be a problem here in eastern NE today... looking at my weather station DP's are only 50 degrees now with a temp of 73... Winds are trying to veer slightly with the wind chaging from the SE to the S at around 10mph... well have to see what this afternoon brings tho as i am no expert... Think most of the action will be just North of OAX and mostly elevated supercell hailers with a strong MCS becoming likely as things go crazy tonight...

 

[Dan Christianson]

I been looking at models, in the past few runs, im liking the Norfolk to Sioux City line, right now, however im getting that gut feeling something could happen towards the Fremont to Wayne line ? im going with Eastern NE to Northeast NE , today hope it holds off till i get off work... PRAYING NOW for a good chase GL everyone watch the speed in NE too the State Patrol dont like us chaser's",

 

[Mike Hollingshead]

http://www.rap.ucar.edu/weather/surface/sfc_ict.gif

If you want to judge the dews for the day I'd look south of the warm front. There are some 70s in northern OK and some 60s into NE.

 

[Nic Wilson]

The 12z RUC appears to have some strange solutions so it will be interesting to see if these are resolved for the 15z run out in a half hour. I am liking the set-up in south central Nebraska out ahead of the sfc low currently near the CO, KS, NE intersection. This is the only area with 500 mb flow favorable for discrete supercell development (~ 40 kts) and should be the focus of moisture convergence in the afternoon. That being said, the RUC is consistent with yesterday's NAM in developing precip. in the western IA I-80 corridor. Hodographs turn nicely in this area, but flow is looking weaker than expected aloft. The dramatic temperature and moisture return expected with the warm front drifting north should create some interesting interactions in the late afternoon and should be watched closely.


Target 1: My favorite target of the day would be the HSI area in so. central NE.

Target 2: Western IA along and north of I-80...*storms here will need to move north of the boundary to tap into better helicity and upper-level winds, definitely a target with a lot of "ifs" today.

 

[Mike Hollingshead]

http://www.wxcaster2.com/CENTRAL_ETA_1000-...PRPTHK_18HR.gif

http://www.wxcaster2.com/CENTRAL_ETA_1000-...PRPTHK_24HR.gif

Both of those are after dark obviously, but for those that like chasing after dark it is quite possible there could be some training mesos that want to back build all night. There was a similar day last year in northern IA a few of you were chasing. That is aside from what may happen before it is dark.

 

[Chris Allington]

Definately hoping those dews can make it here this afternoon... They did just bump up slightly with my station now showing 53 degrees... Temp sitting steadily at 73...winds from the SW at 12 mph.... Tonight could be fairly interesting after dark as Mike points out...

 

[Douglas Mitchell]

Me, Andrew Ashley and Gary Eccles are sitting at a food court type thingy in Lincoln. Debate over whether to head west towards LBF or to stay in OAX area was ended by grunge cover over C NE. I think the RUC is pulling a fast one on moisture return but LCL heights are still the biggest concern. If anything, we'll probably drift Nward towards Wahoo.

 

[Ryan McGinnis]

I'm sticking here in Lincoln at the moment... I'll probably stay here as long as I can, as I have fast, free data. Looks like I'll end up moving north a wee... but not much. Storm motion today will be ENE, which means I-80 may come into play. The roads out here are generally pretty darn good. Hope this one pans out.

It's probably been said already, but keep your mind on the rivercrossing if you're out chasing this way. Omaha is a perfect place to cross, if it's not "rush hour". (Rush hour in OMA isn't exactly like you'd expect in L.A., but it'll still slow you down.)

Just noticed that SPC upgraded this area to MDT, with hatched tube threatbox. Makes me feel better for not driving west this morning.

 

[Glen Romine]

Interesting new day 1 - I think it is the first time I've seen 5% tornado and hatched????? Confidence bolstered by SPC agreement with earlier forecast. So, I'd still suggest hanging close to the OMA area until a more clear target is evident.

Glen

 

[Douglas Mitchell]

SPC has just upped the ante today by issuing a mod risk for the OAX area and a hatched tornado risk. Definitely getting my hopes up a little bit