6/6/09 FCST: NE/CO/KS/OK

[Bryan Stokes]

There seems to be some discussion in this thread for Friday the 5th when it is a forecast thread for Saturday the 6th. It would probably be best to start a new thread for Friday. (besides being a rule, we're talking about what will undoubtedly be two different chase set-ups)

For Saturday, it seems that things are getting pushed further and further east with each model run. It also looks like the cap will be a major concern along the dryline in KS.

Bryan

Edit: My mistake, Skip started a thread for Friday a couple of days ago. I was just confused by all of the cross-talk going on in this thread in regards to Friday. I think I better get some sleep!

 

[Bill Tabor]

When I first saw some of the mid level flow returning I thought for sure Fri/Sat would be good chase / tornado days, but I've been looking and re-looking at the WRF/GFS (12z run) for these two days and it just looks to me like problems for tornadoes IMO. The primary issues as I see them are the cinh due to 700mb temps far north and the lack of strong/sufficient sfc winds in the areas which otherwise would be favorable for torndoes assuming convection breaks out and supercells form. Another issue I see is NAM/GFS placement of low and frontal boundary on Sat are fairly far apart. Appears SPC is leaning to GFS solution with severe further east in IA,MO,eastern NE, and eastern KS, but the NAM is western KS, western NE, CO. I almost always prefer the NAM solution as the GFS always burns me. NAM on Sat would put favorable area in nw KS or sw NE but best sfc winds are in southern KS - go figure - how to make a tornadic storm? Guess the next run is out to make me scratch my head some more. I'm just wondering if we are going to get back into a decent flow without huge inversions to prevent convection this season or will this stagnation continue. Seems it's been awhile since I've seen it this bad. Also a bit hard to get back into chase mode after the 3 to 4 week lull.

 

[Patrick Marsh]

I guess I must be missing something...

The Gulf of Mexico will have northerly winds across the western half of it very soon (at both the surface and H850), if not already. These winds are likely to persist until at least Saturday morning...and it takes until very late Saturday into Sunday to setup any kind of decent moisture transport back into the plains.

The LLJ is forecast to be oriented SW to NE. This will not aid in advecting the deep, rich moisture from the Gulf of Mexico into the plains. Furthermore, a SW to NE LLJ is not typical in a large tornado outbreak. The LLJ should be oriented more S to N. A SW to NE oriented LLJ favors linear evolution.

The trough moves into the plains with a very positive tilt. This results in a more west to west-southwest wind pattern at H700 and H500. Considering that the SW will have been baking for awhile, this will advect a substantial EML a considerable distance to the east. Thus, most of the southern half of the plains should be well capped. To the north of the cap, whatever moisture transport that may take place Friday night with the LLJ should lead to considerable nocturnal precipitation in Nebraska. Convective outflow should prevent the front from retreating north any...and in a worst case scenario...push it further south.

A strong cap, meager boundary layer moisture (by June standards), and a more unidirectional wind profile don't give me confidence in a large tornado outbreak. In fact, if isentropic lift over the warm front is necessary for parcels to reach their LFC (which even the SPC hints at in the Day 4 - 8 outlook) then this will most likely be a bowing line segment growing upscale into a MCS tracking along the warm front event. Even this won't work if the warm front isn't of decent stregth.

With all this said, there might be an isolated tornado threat after 00Z Saturday with any storm that remains isolated at this time along the triple point. Surface and H850 winds should strengthen and back slightly with the loss of daytime heating. This backing will help curve and enlarge low-level hodographs...more so than hodographs to the east.

Just my initial $0.02 from three days out...

 

[Craig McPeck]

After glancing at some data, I would target Southwestern Nebraska, probably North Platte. 3500 CAPE and Shear of 50-60.

 

[Brian Stertz]

I've been watching (and hoping) to see some glimmers of hope Sat. but the cap looks to be a spolier for much of the Plains during daytime hrs. The only hopes that I can see (a target out of reach for me at least) would be across SE Wyoming and the W. Nebraska Panhandle. Here too the ingredients for tornadic supercells do not seem to all be there if the 00z NAM is to be taken for face value. Looks like things will have to wait for Sunday to get me out on the chase trail again....

 

[Rich Thompson]

Patrick M. pretty much covered in a couple of posts back. Relatively meager moisture (certainly by early June standards), the persistence of some form of ridging from TX-KS, and lots of flow from the EML source region suggest many cap problems in the coming days.

If I had to target somewhere for chasing, I'd lean toward the extreme NE CO area on Friday, N of the warmest EML. Saturday looks more problematic because even though moisture will likely increase some from Friday (though the operational models may be overestimating evapotranspiration a little bit), the core of the warmest EML plume will be solidly over KS by then. I know most parameters point toward n central KS Saturday evening, but I'd seriously consider the NEB Panhandle for similar reasons to choosing NE CO on Friday.

Of course, you can take my forecast with a truckload of salt because I will be working and unable to chase

 

[Jeff Passner]

The trend for this system is already set --- it's the upper low in NW Florida and the northerly flow in the Gulf. It's early June and the Thursday dew points will be in the 40s after the moisture mixes at Abilene, Texas. That is amazing... And it's depressing. The trajectory of the Abilene parcel will head toward Kansas... The only way I think this system works for Saturday is to chase the upslope storms in eastern Wyoming as they move into Nebraska because the cap in Kansas looks difficult to break. The shear profiles are excellent north of the warm front but the original parcel (easterly wind) is diverging from the high pressure in Michigan and it looks like low clouds might persist all day and inhibit heating north of the front, if one believes the WRF-NMM. As I said, the upslope component in eastern Wyoming is impressive and a storm could easily rotate there and produce a very nice tornado. However, given the road network in the region (and the mere 900 mile drive for me) I'm going to probably skip this. And to clutter up this situation, the models have been bringing in a fair amount of high-level moisture (cirrus) in nearly each model run....

 

[Warren Faidley]

Glad someone else noted the overall lack of RH, as the low over AL closes the Gulf off for the extended. Looks like the season (in terms of good moisture and tornadoes) is once more shut down until maybe next week if the Gulf can open up. I guess there is the possibility of up-slope pooling in the foothills of NM, CO and WY. I think this will be the play for the near future.

W.

 

[cdcollura]

Good day all,

I guess there is the possibility of up-slope pooling in the foothills of NM, CO and WY. I think this will be the play for the near future.

Moisture will indeed be a problem ... But I never laugh at a 50-55 degree DP in high (upslope) terrain that is 5000 ft+ MSL (Palmer Divide in CO and such). That is going to be the importance if this setup is in W Kansas or NE Colorado.

I see the low in the Gulf is very weak, and should move NE (not stall, hopefully). Opening up the Gulf Friday and get the proper moisture in place for Saturday.

Sunday, moisture issues disappear altogether farther east towards W Iowa.

 

[Sean McMullen]

12z NAM introducing an interesting scenario for Saturday evening. Sometime around or after 0z the NAM develops a storm in central/n. central KS on the dryline bulge. It appears to start off elevated not producing much precip until the evening around 3z. As a 997 low moves into n. central KS the storm seems to become surface based on the nose of a 50 kt low-level jet. It then tracks the storm from n. central KS into southeast NE. Parameters in this region will certainly become more favorable for tornadoes in the evening due to increasing low-level wind shear and moisture pooling. However, it's very conditional because of the strong cap and I'm not a fan of chasing monster tornadoes at night but this is one scenario that needs to be considered.

 

[Skip Talbot]

Parameters in this region will certainly become more favorable for tornadoes in the evening due to increasing low-level wind shear and moisture pooling.

That's how this setup was looking a day or two ago. The WRF has been trending more and more towards a cap bust, however. After 0z the cap index surges up to 5-7, which is completely solid. The 3km cape also drops off to nothing after 0z. This does not bode well for any storm that manages to break the cap in south central NE or KS... its going to be elevated. I think we're looking at a nice clear evening out in the plains on Saturday. I'm reevaluating my plans to chase this day, potentially looking at CO or the NE panhandle where the cap isn't ferocious.

 

[Larry J. Kosch]

NAM 500 MB Loop Looks Good!!

I was looking at the NAM 500 MB loop today. And I was happy to see that the long-awaited upper level low in the Pacific has arrived!

The upper level low will do three things:

1. Break up the high pressure ridge that has kept the Midwest relatively tornado free. It will promote a SW-NE flow across the Midwest by Saturday.

2. Engage the jet stream that has been flying high in Canada and pull it down into the US. Once it does that, it will basically dissipate and a new cut-off low will form right over Florida. It will also allow frontal systems to come into the Midwest.

3. Allow the return of Gulf moisture into the Midwest and create drylines in front of the frontal systems that will be coming down.

Without going into technical specifics, I will say this could be our tornado outbreak of the season coming up. Good hunting chasers! I will probably be bogged down by yard work, etc. But I will be watching the skies this weekend!!

 

[Ken Johnson]

The 00z NAM is starting to look up a bit for extreme northern Kansas and SE NEB. Cape values of 3000 and weakening CIN may lead to a few sfc based supercells. Mid level flow looks good, but low level flow does not. Not until after 00z. The low level jet should strengthen and we should see 0-1KM SRH increase. If storms can remain sfc based then there could be an opportunity for a tornado. If you buy what the NAM is showing, then Concordia up to Seward may be the play...

 

[Melanie Metz]

I like the 00Z WRF run for S Central to SE Nebraska. While I realize the cap is strong I'm hoping something will go before dark. I may be too optimistic but I think we're leaving Friday for a weekend of chasing!

 

[Scott Weberpal]

I'm in agreement that SE NE, based on tonights NAM, will be the place to be. The NAM shows initiation around 00z, however, a worry I have is that the overdone moisture has something to do with the NAM breaking out precip in SE NE. Fortunately, H85 temps are in the low 20s C, and H7 temps around 10c which is doable. Of course, I'm looking forward to the NAM showing a completely different solution tomorrow morning