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

[Skip Talbot]

Although still quite a ways out, models have been fairly consistent in setting up what could be a major event on Saturday, June 6.

If the GFS is correct, Saturday looks like it could be the main event of two days of good plains chasing. The forecasted trough should be well positioned over areas of strong instability, and moisture will have had plenty of time to advect with dewpoints approaching 70 through much of the southern plains. We should see areas with with strong to moderate instability under a 50-60 knot mid level jet from Nebraska south into Oklahoma. In addition, a low level jet will also provide good directional shear and strong low level shear. If this plays out, we'll have an environment favorable for a widepsread severe weather event with supercells and tornadoes. The setup looks similar to Friday's but should be the more dominant event as moisture and upper level support will be more established. Areas further east should be in play as the dryline pushes east with the trough, and areas further north into Nebraska as the moisture has had more time to advect. Also like Friday, the cap looks stout in Oklahoma, we might be struggling to get anything through it, but with the much better upper level flow we might have the dynamics in play for a loaded gun setup in Oklahoma. Definitely one to watch!

 

[cdcollura]

Good day all,

I am watching this (and Friday 6-5 as well) for a potentially "hot" day in W Kansas.

There should be a strong H3 (300 MB) 100 Know WSW flow over a 500 MB flow of up to 60 Knots from the same direction. At the surface, a 998 MB low is progged to form over SE colorado with a dewpoint gradient (dryline) / triple point with DP's from the upper 20's to the low to mid 60's in W Kansas.

About the cap, the 10 degree line pretty much intersects NW Kansas, but the large scale ascent (as the H3 and H5 winds will be difluent) should erode it and allow supercells to develop, especially near and ahead of where the stationary front / boundary intersect the dryline.

 

[Rob Wadsworth]

IF- I were out on the Plains right now - the NW corner of KS/NE corner of CO - is looking interesting. The orographic forcing, the surface temps, the great t/dp, the lapse rate, and the surface low. Modest helicity and CAPE/CINH are there. But - I'm still a beginner at this - so take it easy on me.

 

[Ken Johnson]

This is probably the best looking set up we've seen in over a month or perhaps the entire season. Mid and upper level jet look good. 996 sfc low over western Kansas, with WF stretching east across northern Kansas. There should be a nice dryline/WF intersection across northern or central Kansas. Low level jet looks good too. Both deep and low level shear look good enough for a higher end event..The only problem I see is very warm temps at 850/700 MB which will create a strong cap and that could hinder things a bit. But it's still a ways out and plenty time to watch it. Right now I like northern and central Kansas as well as southern Neb.

 

[Mikey Gribble]

After just looking at the new 00Z GFS I am pretty much getting sold on a tornado outbreak on Saturday over portions of southern Kansas and at least northern Oklahoma if the cap doesn't hold. I don't think it will, but I have no business saying that because I haven't forecasted nearly enough and am not qualified to make any sort of statement like that lol. Right now the wichita and OKC areas would be under the gun later in the night. I'm sure a lot will change, but god it's nice to at least have a chase with some decent tornado potential.

Saturday definitely looks like the more traditional outbreak, but Friday shouldn't be overlooked. It could be another capping issue, but there is some wicked directional shear on Friday in some places. I posted more on the forecast on my blog, but the post was made off the 12Z data. Here is the link if you are interested http://loadedgunchasing.com/blog1/

 

[Jason Boggs]

Saturday looks to be a pretty good day according to the GFS. Good speed and directional shear along with adequate moisture may spark off a few supercells. The cap may be a problem if the GFS is right. Temps of 12-14 at 700mb may inhibit all but the strongest updrafts. This may lead to very isolated storms, which is a good thing. Surface temps in the upper 80's and lower 90's along with deep moisture will help erode the cap throughout the day.

All in all, it looks like Saturday may be the best day (tornado wise) in a long time. Finally were getting good dynamics coming in, along with a fairly strong cap to cook the atmosphere. When and if it explodes, hopefully tornadoes will be the outcome.

TARGET: Right now, I'm liking the area around Ness City and Jetmore, KS.

 

[Bryan Stokes]

It looks like the ECMWF is starting to show a different outlook sending the front further south where the cap is forecasted to be really strong. I sure hope this isn't another wasted set up.

Bryan

 

[Skip Talbot]

Did this change in the ECMWF just appear in the last run? If so I would probably discount it. The GFS has been very consistent with this setup (for once). Also, the WRF and GFS out to 84 hours are very similar, which further instills confidence in me with this solution. Up and down the dryline from Kearney, NE to Salina, KS looks the best right now given the forecast cap strength.

 

[cdcollura]

Good day all,

I sure hope this isn't another wasted set up.

Now-Now ... Let's not get negative guys on the first really positive "chance" in a long time!

I feel that the ECMWF is over estimating the front surging south due to the high to the north. The GFS looks more accurate IMO.

If cyclogensis os ocurring to the west at or below 1000 MB, then it would be very hard for a front to it's east to surge that far south!

I think that with better moisture for this day (6/6) in place, and upslope winds (W KS) and dryline / triple point forcing, the cap has to break, regardless of how strong it is.

 

[Michael O'Keeffe]

The 12z GFS looks very nice with an obvious target near the TP in C NE along I80, say Kearney as a prelim. target at this point. Still a long ways away but as of right now that's where I'd go. The C NE target is also good because much lower LCLs, helicity along the WF will be 400+ m2/s2 at 0-3km and 200+ m2/s2 at 0-1km which is nice to see. The hodos look great up there and the best CAPE is nosing into this region as well as a nice dryline bulge. I like the more breakable cap and good 0-3km CAPE. It is nice to be able to have an slight idea of a target well in advance unlike nearly every setup this season which has consisted of staying up all night trying to find a target!

 

[Chris Allington]

Given that is local and per tonight's 00z runs... even closer to me I have already put in for a day off on Saturday. Both the NAM and GFS are in pretty decent agreement all the way up through the NAM's 84 hours on Twisterdata, which gives me not a whole lot of reason not to trust the GFS beyond that. I havent gotten a chance to look at the Euro yet.

Surface temps in the mid 80's and dewpoints in the upper 60's should give us some pretty favorable t/td spreads. I suspect we will have less mixing problems than we have had in recent weeks due to the rain yesterday. Also, instability values at 00z peak between 3500 and 4000 j/kg. LCL heights in the same area look to be between 750 ft and 1000 ft AGL. The one thing I'm not liking is the largely unidirectional look above 850mb... but SEly surface winds and some speed shear in the mid levels look to offset that somewhat, with about 45 kts of bulk shear. If I were to say now... I would probably start somewhere SW of LNK, say near Wilbur, Nebraska around 3-4pm. This can definately change as we are still 4 days out, but if worst comes to worse I will visit some college buddies in Lincoln and go have some dinner only 60 miles from home.

 

[Derek Weston]

The cap really worries me with this one. Latest GFS run spits out areas of + 12C temps into Kansas. (with borderline 10-12.5C temps overspreading the rest of the favorable chasing region)

Latest GFS run would have me favoring NE quadrant of KS closer to the low.

Could be a big day if things do pop in a timely manner.

Don't like how this system has been inching further east. Nobody wants Missouri and or Arkansas.
(though we've got a fair bit of space before that happens)

 

[Skip Talbot]

12z GFS and WRF are in fairly good agreement with only minor placement differences. I'd say the I-80 corridor in central and western NE looks primed. We've got a stationary front here and a dryline extending down through KS. The moisture looks like its going to wrap around the surface low, destabilizing the atmosphere all the way to the CO/WY border. This area could be a big tornado producer as this area will be highly sheared with enhanced directional shear. I'd also be looking at where the dryline buldges out in south central NE. This looks like a good place for initiation, where storms can fire, mature in the warm sector, and then tap the enhanced directional shear on the stationary boundary. I also really like how the models continue to back the surface winds and advect moisture past 0z Sunday. Conditions will only be improving as the day goes on. Further south, however, a forecasted cap index of 5 from all of KS through OK might keep the dryline pretty quiet. Right now, I'm eyeballing Kearney to McCook, NE where we should have cape over 3000 J/Kg, 60 knots effective shear, and locally enhanced directional shear from the triple point for tornadic supercells.

 

[Ken Johnson]

18z GFS and NAM both continue to show the cap from hell over most of the central states. The only exception is across Nebraska. This area will be north of warm front and just north of strong cap!
Up slope areas in Kansas/Neb may be best bet for tornadic sups,before MCS forms late in the evening at this point...STill time to change, but as a rule, the cap wins out without a good forcing from a decent short wave...

 

[Eddie Natenberg]

When I saw the GFS earlier this week I knew I should be down in the plains, now I have two plane tickets betting on it. I am really liking the 18z gfs its shows strong vorticity advection, I think the cap will be a major issue for the warm sector so I am targeting the northern most part of the warm front on "Saturday". Great shear and good dynamics, I think this will lead to a low coverage event with solid isolated sups, more detailed discussion tomorrow. Hmmmmm...