6/6/07 FCST: ND/SD/NE/KS/MN/IA/MO

[Dave Winslow]

I agree with the high risk potential for Wednesday. One thing that will be more favorable for discrete supercells will be the more robust CAP, and the orientation of the upper flow, more SW to the dryline than May 5 2007 when too many supercells formed and rained into each other with the upper level flow SSW.

My target for now is From Yankton SD to Hastings NE, then wait to see where these speedy storms go and which become dominant.

 

[cdcollura]

Good day everyone,

Looking at the models, I see lots in store for Eastern Nebraska into SE South Dakota. Right now, I am planning on leaving Dayton, OH to make Kansas City, MO for the night on Tuesday (June 5). My primary target is a couple of hundred miles into the Omaha, then west towards York for starters. Right now, trying to clear my schedule for the remainder of this week because after June 6, the "show" goes on until the weekend ;-)

 

[Chris Hayes]

Wednesday is deffinately looking good with extreme instability and shear, ahead of a sharp dryline. I was looking at the SRH on the COD website trying to figure out the storm motion. The storm motion speeds are kind of hard to interprete the COD website. Anyone got any webpages that show storm motion speeds a little more clearly? So far, my target is a triangle from Grand Island to Columbus NE, to Yankton SD.

 

[Chris Wilburn]

The new run of the NAM is out and nothing has really changed. Forecasted 977mb surface low in central SD by 00z with 65-70 td's and CAPE near 5,000 J/kg with a fairly sharp dryline extending from the surface low in central SD all the way through OK and into TX. Helicity and directional/speed shear looks really really good as well. The NAM breaks out precip by 00z in extreme southcentral SD. CAP still looks strong, but there is obviously enough very strong parameters to where the CAP should slowly erode as the day goes on. This could very well be one of those events where tornadic supercells continue to rumble on into the night well after dark. Towns in se SD and ne NE will be under the gun for sure with further activity down the dryline to follow into sc Nebraska into Kansas eventually. It's nice to see the consistency from model run to model run and it looks for sure that this will be a chase day in order for lots of people. I think the further north the better chance of seeing something before the sun starts to set. Early thought is to head to Kansas City tomorrow night and head towards a general area of extreme southcentral SD/extreme northcentral NE say near Valentine or more than likely points just to the east of there and adjust accordingly. I have never chased this part of Nebraska so it will be a nice experience for sure. Still a few more model runs to look at, but things look really good as they stand now. Of course the mentioned SPC moderate risk on the Day 3 is encouraging and I too expect an elevation to high risk at least by the Day 1 that comes out just after midnight and very possibly as early as the 1730 Day 2 run that comes out tomorrow. One more thing to mention is storm speed. Storms should be moving at a somewhat decent clip on the order of 40kts. Will be somewhat of a challenge to keep up at times. Maybe we will get lucky and they will be closer to 35kts.

 

[Jeff Miller]

Wow, what a day Wednesday is looking like according to the models, which have been quite significant.

Storm motion should be favorable for classic chasing with a SW-NE mean storm motion as well - unless of course the sups right turn which is of course typical sup behaviour.

Shear at the 850/500 looks terrific with south at the 850 and SW at the 500 providing more than enough shear for significant rotation - in fact, SRH is nearly off the charts according to the 60 run. Definately the potential for significant severe thunderstorm activity and agree with SPC analysis for the potential of strong to long track tornado activity considering the combination of shear and updraft intensity and low LCLs.

At this point, am thinking potential highest probability targets are going to be within a box from O Neill, NE to Sioux City NE to Sioux Falls, SD west to Mitchell, South Dakota. Early call for target bullseye currently stands at an O Neill to Yankton line for initiation and subsequent rapid tornadogenesis.

This system will be fed dynamically by an especially vigorous upper low for this time of year - and while conditions are always subject to change, confidence for this is high in my opinion.

If a chaser is to chase once this year, this would likely be the day if you're in it for tornadoes. Someone is likely going to bag a strong tornado Wednesday.

Charge the camcorders, get extra batteries, check the car, and see you in my neighborhood on Wednesday!

 

[Jeff Snyder]

Wednesday certainly looks pretty good from many perspectives, but I have a one significant worry. My primary concern pertains to the degree of forecast moisture return. Current surface observations indicate that one must go all the way to the Gulf coast to find a batch of >70F dewpoints, north of which there are widespread northerly surface winds. Looking at the NAM progs, it appears that some locales in NE and KS see a 8-10F dewpoint rise between 12z and 18z Wednesday, with a huge batch of 70F Tds showing up rather mysteriously. It doesn't look like those 70F tds are advected in from the south (though, looking at the 850mb Tds, there will be strong northward transport of moisture above the surface Tues night, moisture this is mixed down to the surface as the convective boundary layer develops Wednesday morning), so I can only assume that a good deal of the moistening is related to evapotranspiration. This isn't bad, obviously, since we're in June near the corn belt, but I don't like to depend upon evapotranspiration when we have as strong of low-level flow as we'll have (tends to increase mechanical mixing, which may wipe out some of the Td contribution from ET). This will obviously have implications on cap strength, and it will affect LCL height. With temps in the 80-90+F range, I think we really need >68F tds to have manageable LCLs (and a manageable cap).

Otherwise, I agree with everyone else. Potential for long-track significant tornadoes is relatively large, as it looks now. If Tds don't reach the upper-60s or higher, I think this potential will be reduced, however. That moisture has an awful long way to go, unfortunately. With cap and moisture questions attm, I'd stick with a MDT.

 

[Darren Addy]

Just a couple of other things to keep your eye on, as Wed. approaches: Nebraska is not going to be completely dry between now and Wed. so it will be interesting to see how rainfall and possibly outflow boundaries enter into the mix by Wednesday's event.

I also find it interesting that the LBF (North Platte) forecast discussion today is anticipating cap breakage by NOON on Wed. with storms moving INTO the moderate risk area in NC Nebraska (as opposed to initiation within the mod. risk area). They also seem to anticipate a SLOWING of the system as it comes out of the Rockies (and thus a corresponding movement of Wednesday's moderate risk area somewhat west of where it is is showing today). Full text of the Nebraska office's forecast discussions here: http://www.weather.gov/view/prodsByState.php?state=ne&prodtype=discussion

This one is going to be fun to "dial-in" on between now and Wed. morning.

 

[Donald Giuliano]

I think Jeff makes some great points about the moisture return, LCL height, and associated capping--looking at the way dewpoints plummet Wednesday night in the warm sector is enough to make my toes curl. I share his concerns, and would add to that that even with dewpoints in the 68-70 degree range, the capping is still very, very substantial, with only a narrow corridor of low CIN, even over SD/NE. To really kill the cap and allow for sustainable convection into the nighttime hours a la May 4/5 of this year, mixed-layer dewpoints more in the 71-73 range are necessary, which is not going to happen.

So given that it looks like moisture return won't be stellar given the strength of the cap, what if the models are overdoing 700mb temps and the cap is not really what it's advertised to be? This would hardly be unprecedented, but this time the cap looks all too realistic. After baking under a ridge Tuesday, all the hot air from the Rockies is rapidly advected east by intense 700mb flow ahead of the trough on Wednesday. That's obviously favorable for steep mid-level lapse rates, but in this case is too much of a good thing, I think.

As a consequence, I think Wednesday will not be a record-breaking, monster outbreak, simply because there won't be enough storms for that to happen as the cap is too much of a limiting factor. That said, the shear and instability are obviously out-of-control, so wherever storms are able to fire and sustain themselves (most likely a few cells in SD/northern NE), I'd certainly expect them to tornado in short order. Wish I could go up there, but there'd have to be no obvious negatives to get me to go to SD during the week. With the models forecasting a huge cap in place over the vast majority of the warm sector despite a bullish moisture forecast, I'm going to have to take a pass.

 

[Al Leese]

I am planning on leaving Dayton, OH to make Kansas City, MO for the night on Tuesday (June 5).)

Likewise, I just bought my plane ticket (from D.C. to K.C.) for Tuesday night. Target as of now is SE NEB. Might be quite a convergence!

Safe traveling to all!

 

[Craig Maire II]

6/6/07 FCST: ND/SD/NE/KS/OK/TX

I will be taking off tomorrow afternoon and getting a hotel room near Sioux City Iowa or Sioux Falls South Dakota tomorrow night. I do believe that there will be a significant tornado outbreak on Weds and that the extreme shear, instability (I believe that there will be plenty of moisture for strong tornados and significant supercells) strength of the low etc. will provide a very nice chase event for the folks who go chasing on this date. Will someone include Iowa in the above title please?

 

[MatthewCarman]

Wensday looks like it could be asome but it is still several days out.

With chasing on Wensday the MOD risk looks to be around the MO river. Is there alot of places to cross on the MO river? I have read before that people dont always like to play near the MO river and that is why I ask.

SPC already has a moderate risk and all of the conditions appear to be favorable besides mabey dew points not getting as high as forcasted so if the cap breaks I would still expect alot of severe weather. When storms are able to break the cap in a area and move into a capped enviorment will that kill the storms or will they beable to break any capped area they move into?

This is a day to keep your eye on and so is Thursday,Friday and possibly Saturday for parts of the Midwest and Mideast area.

IA/MN/MO/WI should be added to the title and TX should be removed. Could the mods please fix the title.

 

[Josh Richardson]

I have already taken the day off as well and am targeting a Yankton to O'Neill area, make my decision later on as of course its still aways away.

 

[Mark Farnik]

I will be chasing with my new chase partner Carey Walton on Wednesday. We plan on leaving Fort Morgan about 8 a.m. to reach our target of Ainsworth, NE by 3 p.m. CDT, which will allow us a couple hours for target adjustment before initiation. I'm very excited about the tornadic potential for Wednesday afternoon/evening, despite the prominent cap. I think the shear/instability and moisture will be more than adequate to breach the cap by late afternoon.
I anticipate isolated supercells will initiate in north central NE/south central SD between 5 p.m. and 7 p.m. CDT and will rapidly become tornadic. Cyclic supercells as well as strong/long track tornadoes look probable.
I'm pretty sure the chaser convergence in northeastern NE/southeastern SD is going to be absolutely ridiculous Wednesday afternoon...
Happy hunting to all; it looks like it's gonna be one helluva chase day!

 

[David Wolfson]

The new GFS is -- surprise, surprise -- pulling everything majorly backward. 700mb 12C+ over eastern SD and NE combined with best low-level shear and upper diffluence further west now points toward [V] target of Pierre, SD. I think finding the point somewhat southeast of the rapidly deepening surface low will be the best for discrete supercells, so dialing-in to use Darren's word will be the job first thing Wednesday morning.

 

[Skip Talbot]

With chasing on Wensday the MOD risk looks to be around the MO river. Is there alot of places to cross on the MO river? I have read before that people dont always like to play near the MO river and that is why I ask.

You are going to be playing the western region of that Moderate risk if you want to get on these storms at initiation. Given that the dryline is forecasted to be in central NE/SD, the MO river should not be a problem unless you are chasing into the overnight hours. If the system is slower than the models depict, as often is the case, you'll be even further west.

IA/MN/MO/WI should be added to the title and TX should be removed. Could the mods please fix the title.

SPC specifically mentioned Texas in the outlook for more isolated activity. Some chasers opting for a more local chase, may have a shot at some discrete, isolated supercells if they play the southern portions of the dryline.

If the inhibition plots remain as the WRF is currently displaying, I think an area anywhere from central SD south to I-80 is fair game for storm initiation. CINH values between 25-50 and a cap index of 1 in this region can easily be overcome by the strong moisture convergence, and lift from the strong diverging flow aloft. The WRF is plotting positive vertical velocities into central Kansas. Helicity values are actually more favorable south of SD. I'm targetting an O'Neill to Grand Island, NE line for a 0z initiation with the capping inversion being the greatest influence on where this target settles.