6/7/09 FCST: NE/IA/KS/OK

[Michael O'Keeffe]

Since it appears Fri and Sat may be moisture starved it appears we may actually have the moisture in place by Sunday and boy could it get pretty insane over E NE/W IA if tonight's 0z GFS verifies! A 993mb low, top with a powerful and compact negative tilt trough, a 50+knt. 850mb jet, 3500+ j/kg of CAPE, and upper 60-low 70 dew points is a dangerous combo for significant tornadoes and by the looks of it things could get very intense.

Check out 0-1km helicity and EHIs!
http://beta.wxcaster.com/models/gfs/central/CENTRAL_GFS_0-1KM_SRH_96HR.gif
http://beta.wxcaster.com/models/gfs/central/CENTRAL_GFS_0-1KM_EHI_96HR.gif

 

[Brandon Sullivan]

While I haven't given up on either Friday or Saturday yet, I totally agree Mike.. The last time I have seen the Sig Tor Parameter Spike at 37 was well... NEVER!

Aside from the composite indices though, from the 00z and the 6z WRF which go out to 12z and 18z Friday Respectively, I indeed see a very nice setup coming! Wind Fields are looking to be stronger in some places than previous days, including the surface and H5, and moisture already appears to be returning nicely by those times..

One must be cautious though with the GFS constantly having feedback issues, and it could be causing the maximas of many things over the area, although I would totally be happy if it were not..

After a talk with another chaser.. Vortex95 Recorded 5000+ CAPE and 1000 SRH just east of a violent tornado.. That STP was 30..

 

[Craig McPeck]

Latest GFS looks quite good with first storms developing in Eastern Nebraska. Have a nice 2000-3500 CAPE in Eastern Nebraska combined with good shear. Moisture doesnt seem to be a problem. With all these great parameters and finally some good moisture, it appears that Sunday will be a good tornado producing day

 

[jshields]

the 12Z run of the gfs has backed off on the intensity of the low and the wind fields, but still look good a little further east into iowa. i will be camping up in niobrara til sunday morning so i hope everything holds off til later in the day after i get home. i hadn't noticed 0Z runs until i saw this post. did anyone look at the skew-t/hodographs for northeast nebraska from the 0Z 6/4 run for 0Z 6/8? i have NEVER seen a hodo like that

(note: time sensitive but twisterdata lets you pull up previous runs of course)
http://twisterdata.com/index.php?sounding.x=476&sounding.y=295&prog=forecast&model=GFS&grid=3&model_yyyy=2009&model_mm=06&model_dd=04&model_init_hh=00&fhour=96&parameter=SHRM&level=500&unit=MB&maximize=n&mode=singlemap&sounding=n&output=image&archive=false&sounding=y&sndclick=y

 

[Adam Penney]

I certainly will be out chasing this day. 12Z GFS while yes it has backed off from last nights 0Z, still showing a good setup across C/SC Iowa. 50kts of bulk shear still with 3500+ SBCAPE at 0Z with (as Michael mentioned) a very nice negatively tilted trough plowing on in.

Still a few days out, but certainly at this time, looks like the best possible show of the weekend.

 

[Brian Stertz]

12Z NAM would say there are split targets for Sunday 6/7. Best target to me looks like Extreme NE Colorado into SW Nebraska. There is plenty going on there to get some legit tornadic supercells underway by late afternoon. The cap looks well cooled off in that area to let convection become sfc based in a hurry...plus a nice compact neg. tilted shortwave is in that area as well. Add in some good upslope and 50+ kts. of deep layer shear and things look quite good there. A more conditional supercell and tornado threat area looks to be over NC/NE Kansas into SE Nebraska and possibly NW Missouri and SW Iowa. This should hold off until the evening time as the cap looks pretty tough still up until 00z and possibly later than that. The severe wx parameters are pretty heightened in this area but again the cap is a significant factor. I am liking more and more the west target for tornadoes, and will continue to monitor that chase option.

I may take off Sat. night from KC to get out into the zone (NE Colorado) for conv. initiation. It would be nice if the closer in target verified with solid sfc based supercells, but it looks like a short window gamble at this point. Things are subject to change...the way this spring has gone.

 

[Skip Talbot]

I can't get into this forecast too much yet. There are still big differences in the models. The GFS is screaming Iowa and has no play further west at all. The GFS has a triple point up by Sioux Falls with a dryline extending south from there and a warm front east. The best jet energy has moved off the western plains. The WRF, however, is slower in moving the trough and has moisture pooling up against what appears to be a sagging cold front extending all the way back to Colorado. I think we're going to have to wait and see what goes down Saturday before we can really nail down a target for Sunday.

 

[Dan Rupnow]

Thinking WI and IL should be added to this thread as well. Todays 12Z NAM shows surface temps of 75-80F in SW WI and NW IL at around 21Z sunday, along with copius boundary layer moisture in the form of 65-70F surface dewpoints thus creating favorably low LCLs over this area. Weak surface cyclogenesis over C IA should aid in 15kt S/SE surface winds over SW WI and NW IL at around 21Z. Winds show good turning with height in the low levels, and solid 50kt W 500mb flow over the area, along with 60kt W/SW flow at 250mb providing good upper level support. SB CAPE is progged to be at 1,000 to 1,500 j/kg and unlike saturday, it doesn't look like a bullet proof cap, as the NAM shows it gone around 21Z in SW WI and breaks out precip there at that time. Not exactly the best chasing country, but I will definately take it at this point!

Edit: 18Z NAM is out and moves the boundary S into IA and perhaps W IL. No CAPE at all in WI, NAM cant even make up its mind. Just hope it doesn't end up being another cap bust!

 

[Andrew Pritchard]

the 12Z run of the gfs has backed off on the intensity of the low and the wind fields, but still look good a little further east into iowa. i will be camping up in niobrara til sunday morning so i hope everything holds off til later in the day after i get home. i hadn't noticed 0Z runs until i saw this post. did anyone look at the skew-t/hodographs for northeast nebraska from the 0Z 6/4 run for 0Z 6/8? i have NEVER seen a hodo like that

(note: time sensitive but twisterdata lets you pull up previous runs of course)
http://twisterdata.com/index.php?so...put=image&archive=false&sounding=y&sndclick=y

That hodograph and the extreme composite parameters were largely lying due to enhancement from feedback issues on the GFS. Still a very dynamic and potentially potent system on hand, but you have to be very careful how quickly you fall in love with such high output numbers like that.

GFS right now is pointing towards a Fort Dodge, IA. Good 50 knot jet at the mid levels, but the low level jet has really tanked on this morning's run. That's a big downer for any hopes of significant tornadoes. The best low level jet is now placed over Illinois and Wisconsin, making me think the warm front should be watched in those areas as well.

 

[Craig McPeck]

Is it me, or does the newest gfs runs that came out look much further south then any earlier model runs today. NAM has remained consistant with this system bringing it further north. So we shall see what tonights data brings.

 

[Adam Penney]

If tonights 0Z NAM verifies, there will likely be no show across the warm sector. What looks to be a very strong CAP will hold strong throughout the day Sunday and through the evening as well.

 

[Craig McPeck]

Too me this set up looks a bit familiar to the Hallam Nebraska Tornado Outbreak. Most of the warm sector in KAnsas also didnt have many reports of anything, as to what you are saying above.

 

[Ken Johnson]

The 00Z NAM does break out precip after 00z, which makes since since the mid level cooling should weaken cap. I like the area from DDC north in SE Neb.

 

[Melanie Metz]

After looking at 00Z NAM I still like OMA area in general for Sunday, at this point anyway. It will be a fun weekend of chasing with targets in SE Nebraska (give or take a little) both days! Hoping for a "boom" one of the 2 days.

 

[Scott Lincoln]

Too me this set up looks a bit familiar to the Hallam Nebraska Tornado Outbreak. Most of the warm sector in KAnsas also didnt have many reports of anything, as to what you are saying above.

And on that day, there was more than just the monster tornado at Hallam, there were tornadic supercells forming all along the warm front and a nearby outflow boundary. I believe there was almost 20 tornadoes in IA/NE that day.

I remember the warm front being a bit more defined during the May 22, 2004 outbreak, however. It also looks like the NAM is slowing the system down according to this run, and the system might still be hanging around the interior plains into Monday.