5/29/08 FCST: SD/NE/KS/IA/MN

[HAltschule]

Yes, indeed. 13z Outlook has upgraded much of the IA/Eastern NE area to a HIGH risk of severe storms. While warm front placemtn is not 100% certain due to model differences, it certainly appears that extreme shear and helicity will allow for some major/strong, long lived tornadoes later this afternoon and evening.

Lets just hope that any tornadoes that do form will stay away from populated areas. We have had WAY TOO MANY fatalities this year already!! Here's to keeping a hopefuly thought.

 

[Jesse Risley]

The SE flow is fairly strong, so I see no problem in getting the warm front to move far enough north by nightfall. However, I agree that overnight poses a problem for moisture return, but instability should be sufficient, or at least partially compensated for by the other good parameters.

The 12 hour forecast soundings at Lincoln and Omaha showing strong 0-1 KM shear (progged to be about 40+ kts) and favorable SRH for some tornadic supercells. It could be an interesting day if everything verifies.

 

[Mike Peregrine]

The RUC is forecasting the ingredients for a strong tornado day. RUC2 shows strong area of CAPE in western Kansas and western Nebraska at 18z, with Theta-e convergence running up and down the dryline. By 21z, CAPE that is well in excess of 4000 j/g has now overspread much of Nebraska, including south-central and southeast Nebraska. 500mb winds are cruising up from the southwest at 40 kts. Lowlevel buoyancy is also impressive across much of Nebraska and down into Kansas, with 0-3km helicity values at 450-500 m2/s2. Due to the strong instability and impressive shear today, there could be several large, long-track tornadoes.

If I can make it up there and if my car keeps it together, I will target highway 81 anywhere from Belleville, Kansas to Hebron, Nebraska today. The warm front should ride up north of GRI by late afternoon, but I'm hoping the storms to the south initiate first by mid-afternoon. The high shear environment should allow for tornadoes to the south of the WF.

 

[Jeff Snyder]

I'd be a little cautious with the RUC since it also forecasts >70F Tds from the SD/NE border southward, which will not verify. Current obs show the solid >=67F Tds from ICT southward, and I'm not sure I can believe that it will advect all the way to the SD/NE border. 64-67F Tds seem likely, so the overforecast of Td on RUC will likely lead to an overforecast of CAPE. Granted, potential instability will be relatively high, but probably not to the degree that the RUC is forecasting. Such an overforecast will also have an effect on SPC Mesoanalysis graphics since the RUC forecast is used as the first-guess field in the analysis.

Dan Dawson, Robin Tanamachi, Nick Biermann, and I are heading up to the KS/NE border region from OKC momentarily. We'll likely end up somewhere between Hastings, NE, and Osborne, KS. It's a little disconcerting to see the 4km EMC WRF congealing convection early into a squall line(s), and the NSSL 4km WRF does similar. It looks like the "initiating boundary" is a little more parallel to the deep-layer shear vector than I'd like, and modest dewpoint depressions may be aiding the generation of relatively strong cold pools. If it looks like convective mode will be short line segments, we'll probably drop south to play the tail-end charlie which may be as far south as central KS. If storm mode can remain discrete for several hours, I'd expect to see an appreciable siggy tor threat. I'd also like to see the 850mb flow back a bit (it's forecast to be from SSW to SW), since I've had little success this year with veered 850mb flow. I'm largely limited to the areas S of I80 today (by time constraint), so I haven't paid much attn to the NE NE and adjacent areas of SD and IA. As such, the exclusion of said threat area from my post should not be interpreted as my forecast of reduced threat in those areas.

On to the KS/NE border...

 

[David Draun]

Umm, I've never chased a HIGH risk before. Looks like I will get the chance to today. We are currently sitting in Salina, KS ready to leave for Grand Island, NE by 10AM. A series of shortwaves will track over eastern NE and western IA. A speed max is shown at 500mb over the area by 00Z as well. I'm a bit worried about cloudiness, but it appears the warm sector goes completely clear west of the dryline. I think storms will initiate between 2-4pm and with backed surface winds, they should turn supercellular/tornadic in a hurry. Stay safe out there everyone, and good luck.

 

[Edward Ballou]

Much like Jeff, I am limited to an area, except the opposite area - NE/SD. The NAM is showing high Tds (upper 60s).

Yankton at 0z

The models are probably blowing this forecast out of proportion. I think we'll position ourselves at either Lake Andes or Yankton with the option to pop south into NE.

Heat and moisture - that's key right now.

Road Construction Note: I've been advised that there may be road construction on the bridge over the Missouri by Yankton. The bridge is open to cars but closed to trucks.

 

[Aaron Kennedy]

Same boat as Ed... we'll be dropping south from Grand Forks momentarily. Tentative target is Sioux Falls (or at least as a data stop before refining even more). Wouldn't be surprised if we end up near Yankton or even into eastward into Iowa depending on how the WF sets up.

 

[Heidi Farrar]

Earl's NAM Skew-T page is showing some pretty crazy stuff from 21Z-06Z across NE & KS. EHI over 11 in Grand Island (03Z) and 9 at Beatrice (06Z). The GFS Skew-T isn't painting things quite so outrageously, but when it comes to EHI >4-5, that's still there. Seems like the GFS is pushing things a little more east, also.

 

[Chris Hayes]

Going to target a corridor from Grand Island to Lincoln. Dewpoints are already getting well into the 60s across southern Nebraska, with 68 at Holdrege. Watching a satelite loop, it's good to see the cloud cover eroding from west to east. Should allow instability to build with time.

 

[Brandon Sullivan]

The last time I thought models were over doing moisture and other parameters IA got an EF-5. So I try not to think that anymore

The environment looks very setup for the forecasted severe weather outbreak later today.. A quick look at the 13z RUC shows the stronger CAPE being confined into NE. Just from a look at last nights stuff and a look at GOES this morn, and ASOS I am looking around the Lincoln area or maybe into York again.

Good Luck All.

 

[David Wolfson]

Currently with others in York, NE (Stupid 8 Motel). The likelihood of nocturnal convection in north/northeastern NE and my respect for ua impulses that reflect in unusual severe, e.g. last evening's NM storms, made me doubt going too far north last night (Norfolk - Yankton) and wanting to keep a good west option open in case the picture painted initiation further west nearer the dry line.

So far this picture seems to be unfolding. Theta-E advection and clearing seems to be sweetening farther west and a subtle low is in place around Sydney. Add the above-mentioned ua feature and there's not much to say against at least going west to Broken Bow - Kearney to catch initiation moving a little north of west at 30+ kts. Oy, here we go again.

Final recommendation to the team a/o 14Z: Elm Creek, NE

 

[Paul Knightley]

Some models (e.g. ECMWF) are showing a somewhat veered surface flow across much of the high risk area (i.e. SSW) - a slightly backed surface flow seems, from ECMWF, to be across the NE/KS border area, SW of Hebron. Also, best 700 hPa LIs exist from Hill City to Hastings by peak heating. Am still considering options at the moment, but may head to Hebron or Hastings and take it from there.

 

[cdcollura]

Good day all,

Currently sitting in York, Nebraska. Conditions appear to be coming together for a major severe weather outbreak (including strong / violent tornadoes). Dewpoints here are already in the low 60's and may approach 70 by late in th day.

I will be targeting anywhere from York to maybe Grand Island and work my way northest depending on the evolution of the warm front, which should establish itself between York and Norfolk with time. A dryline will move in from the west later in the day.

Good luck to all out there today, and stay safe!

 

[Dustin Wilcox]

My forecast hasn't change from yesterday so it's still on page 1. I just wanted to chime in and say watch out for the flooding, much of the target area has seen excessive amounts of rain lately, rivers in the area are running higher than they have in many many years, throw more water on things and there is going to be major problems...

 

[Ben Prusia]

I will be departing from Gardner within the hour for a target as of the moment of Grand Island, Nebraska (will evaulate again at the truck stop at I-29 and IA Highway 2).

Surface OBs show dewpoints already getting in the mid 60's in central Nebraska with 64 at 9AM in Grand Island. Visible Satellite reveals cloud cover moving east away from the western fringes of the SPC's High Risk area for today. Models are different on placement on the warm front and feel that the triple point may be a fair game target to start out with. With the RUC model being sorta believable in terms of dewpoints and instability, it reveals that targets north of I-80 to the vicinity of the NE/SD border could be in for a long day, but it all depends ATM on where this warm front ends up heading to.

Good luck everyone.