5/22/08 FCST: NE, KS, TX, MO, OK

[Bob Hartig]

I'm starting this thread because Thursday is actually the date I was eyeballing yesterday. Have to say, what a difference a day makes, and even a single model run. It's a massive system with a good, deep low, but while I want to get excited about the abundance of strong CAPE and rich dewpoints, it all seems to be well removed from upper level support. From 700 mb up, the wind fields just wimp out; H5 and H3 jets are well to the west of thermal energy. I want to head for the high CAPE and backing winds in southeast KS, but right now, the triple point seems like the best bet.

My hunch is, this'll work itself out in future model runs. I hope so. This Great Lakes chaser is hungry.

 

[Mike Hollingshead]

I'd about bet this is the one day that will probably not be changing a whole lot by the time it gets here. I'd assume the big trough will be out there and near enough by for some mid-level support. I'd also assume the low levels, including 850 will be highly backed this day. I'd guess sw NE into the NE panhandle and portions of ne CO will be the best bet this day. As crappy as the 12z GFS evolves it still looks really good out there on Thursday. Hard to beat the 500-850 crossover showing right now. Almost 40 knot ese 850 under up to 50 knot southerly 500(maybe ssw or sw...but I doubt it). I just doubt this one looks a heck of a lot different by Thursday(jinx).

 

[Mikey Gribble]

I was thinking the same thing Mike. If the trough stalls like the last two runs of the ECMWF shows, then one good side to that is that we'll maintain really good directional shear for several days. Thursday looks like the most probably day for good directional shear and breaking the cap. We should have good moisture in place after 36-48 hours of a backing LLJ, which should get a good fetch off the gulf. I still don't think the trough is going to stall as long as the ECMWF shows and I think it will move out into the plains on Friday, regardless of that Thursday should still be the day before the day event. The difference between this setup and most others is that the slow progression of the trough will allow for two days of moisture advection leading up to it. Typically with faster moving troughs we only get one day of moisture advection before the day before the day event, and as a result the cap is more difficult to break. This time it should be pretty soupy out there and I think breaking the cap on Thursday is a very real possibility. With excellent directional shear in place tornadoes would be a good possibility.

 

[Doug Mitchell]

Yes, it's 5 days out.
Yes, the cap will be an issue.
Yes, Hollingshead wants to poo-poo on the day because of a lack of upper-level support.
But here's my forecast for Thursday.

 

[Derek Weston]

Actually not a bad looking setup on the lastest run here... If the system slows up like the GFS seems to think -- GFS actually looking better here -- it's going to be Nebraska and maybe N Kansas three days straight. Good for gas tanks. And like Mikey pointed out....hey, directional shear, man.

 

[Warren Faidley]

After reading most of the AFD's and a few HWO's throughout the Plains, I'm sure the risk area will be moved south and west to account for the dryline which could be quite active -- overcoming the cap. Regardless, something BIG and unusual is likely to happen with this dynamic of a system in late May.

W.

 

[Mark Farnik]

This morning's Day 4-8 Convective Outlook put a huge smile on my face. After a seemingly endless spring of mostly unchaseable Southern Plains and Ozarks outbreaks, it looks like we are finally going to see our first widespread severe weather outbreak of the year in the Central and Northern Plains, and if what the latest runs of the EMCWF and GFS are showing come to fruition, it's going to be a BIG DADDY!
I think that the end of the week may bear witness to the first significant High Plains tornado outbreak since March 28, 2007, which may very well be a multi-day event, given the sluggish ejection of the upper trough. Thursday looks to be a western NE/KS day, with the dryline forming over eastern Colorado and pushing into Nebraska and Kansas by early evening. While Thursday will likely be a great chase day, and I'll undoubtedly be out, it is Friday that both excites and unnerves me.
In this morning's AFD from BOU, they mention the possibility of the dryline backing all the way up against to the Front Range on Friday, which would allow 50-55 degree dewpoints to surge as far west to the I-25 Corridor and 55+ degree dewpoints as far west as the Fort Morgan/Limon area. With strongly backed 40+ knot east/southeasterly surface and 850 flow, veering to south/southwesterly or possibly even southwesterly flow up to 50 knots at 500 mb, the directional shear is going to be somewhat insane. If the models are even remotely in the ballpark, and if the dryline does indeed retreat that far west, as it moves off the Front Range during the late afternoon hours, the cap will be overcome and the dryline will light up with supercells, with a very strong possibility of tornadoes over northeastern and east central Colorado.

The following is slightly off topic, so I apologize to the moderator's in advance for that.
I guess the reason I'm unnerved by this setup is the fact that a lot of high schools will be having their graduation practices and baccalaureates Friday afternoon and evening (mine is one of them). Also, where it is Memorial Day weekend, the campgrounds at the lakes and reservoirs will be swamped with hordes of campers and boaters.
My greatest concern stems from the fact is that we have not had a tornado outbreak in this area in almost a decade. The last time we had a significant, widespread tornado outbreak in northeastern Colorado was May 17, 2000. The last time we had a significant tornado in northeastern Colorado was also 8 years ago, an F3 on July 5, 2000 near the small town of Dailey.
We have not had a signifcant outbreak or a significant tornado since, and area residents have become EXTREMELY complacent in the last 8 years towards tornadoes. The combination of the timing of this potential outbreak, along with the complacency from nearly a decade without an outbreak, could have some very, very bad consequences if it occurs.

I'm not saying this is 100% for sure going to happen, obviously lots of things could change between now and then, but I personally have never seen a setup that could be so potentially favorable for a widespread tornado outbreak over eastern Colorado in many, many years, and the models have been fairly consistent in their handling of the evolution of this trough (for once).

And, of course, I can't chase on Friday, seeing as I have my high school graduation practice that afternoon and my Baccalaureate that evening.
I want to track down Murphy and strangle him with my grad tassle!

But who knows, maybe the tornadoes will come to me...

 

[Mike Hollingshead]

Yes, it's 5 days out.
Yes, the cap will be an issue.
Yes, Hollingshead wants to poo-poo on the day because of a lack of upper-level support.
But here's my forecast for Thursday.

Yes because that run of that model had the upper jet about 300 miles west of the dl, lol. Mid-upper was also running parallel with it. The area that could work well is north of the dl arc in the moist tongue stretching back west....IF there was a moist tongue with any n-s depth. Seems the very strong backing wants to advect in drier air and sort of hamper that idea...at least on that run of that model. I expect to need to be way west on these, but am hoping not...mainly to have a few road options to share with the billion others that will be out.

 

[Mikey Gribble]

I just copied and pasted part of the forecast from my blog...

A strong low level jet will begin advecting moisture northward as early as Wednesday morning. With good moisture in place over the gulf, 36 hours will be more than enough to advect low to mid 60 degree dewpoints into western Kansas by Thursday afternoon. With good surface heating surface temps should climb into the upper 80's over the warm sector with SBCAPE >3000J/kg. An extremely strong surface low located in the vicinity of NE Colorado will back low level winds across the entire warm sector. When combined with backing 850mb flow AOA 25kts and at least 90 degrees of turning in the 0-6km layer, the shear profile will be quite favorable for tornadic supercells. The biggest concern as of now is the cap. It is too early to speculate on whether or not the cap can break, but 850-700mb temps are toasty and it is making me a little nervous. If the cap can break along the dryline in western and nortwest Kansas, tornadic supercells will be likely. The cap may be a ***** though.

I haven't looked into it a whole lot, but I am seriously worried about the cap. I hope it can break a little ways down the dryline because the conditions should be quite favorable for tornadic supercells coming off the dryline in NW Kansas, where the warm sector will be narrow enough for storms to interact with the warm front (where SRH will spike). Along the warm front the GFS has the sig. tornado paramater up to 6 and 1km EHI is some where around 5. Not bad for the day before the day chase, but it won't do us any good is there aren't any storms.

 

[Michael O'Keeffe]

The latest WRF looks VERY good for Thursday. I am quite impressed with the look of the system. As of now I'm throwing the GFS down the toilet and looking at the WRF it is amazing. The trough is really coming out of the Rockies by Thursday. Man I hope this verifies! As of right now W NE into W KS down into W OK/E TX Pan look best as long as the cap breaks.

Here are the 500mb winds for 00z Thurs. What a trough!!
http://www.rap.ucar.edu/weather/model/eta84hr_500_wnd.gif

 

[Jim Leonard]

Michael, I agree. I like the area near Goodland Ks. as a starting point for Thursday. Your right the gfs needs a good flush..

 

[Brian Stertz]

The WRF sure looks pretty incredible up for EHI there by Sidney NE on Thursday. I am also liking along the dryline for maybe some evening development from SW Nebraska into extreme NE Colorado and NW Kansas. The parameters are pretty much on the high side if a supercell or two does fire there. Time to keep a watchful eye on how that cap is handled. Looks like the cap surely is breakable up there east of Cheyenne WY by afternoon. That would be my target area if I was able to chase.

 

[Gabe Garfield]

The latest WRF looks VERY good for Thursday. I am quite impressed with the look of the system. As of now I'm throwing the GFS down the toilet and looking at the WRF it is amazing.

Forget that! I'm going to disregard both the GFS and the WRF and I'm going to draw my own system!

It'll look something like this:
http://www.spc.noaa.gov/publications/thompson/3may99/cfig10a.gif

Seriously, though, Thursday looks very good (per the WRF forecast). I'd be even more optimistic if the GFS generated such a solution, since it is a global model (it has a larger domain and accounts for features outside of the CONUS). Be that as it may, I think Thursday has good potential regardless of what model you take into consideration.

Right now, it seems as though western Nebraska and northwest Kansas will be the hotspots on Thursday. Moisture/instability should be fantastic by then, and shear profiles should also be fantastic, provided the upper low is as progressive as the WRF suggests.

 

[Mike Hollingshead]

This has seemed like the safest day, since it seems certain you'd have the strongly backed low levels, and better juice by then. It also seems like it's been the day the trough really deepens(or becomes the most nicely established), and before it does much of any retrograding(or splitting apart). I agree with Brian about Cheyenne'ish as good op, but am still reminded of March 28, 2007 on this one. Winding up around Imperial NE wouldn't surprise me, closer to the ne side of the DL arc.

 

[Mark Farnik]

I agree with everything that has been said about Thursday in the last few posts. I would expect the most concentrated area of tornadic activity to be in a corridor along and east of a line from Bridgeport, NE to Sterling, CO to Sharon Springs, KS. I'm going to take a gamble and say there will be four to eight isolated tornadic supercells, some possibly cyclic, over the course of the evening in this area.
Given the awesome predicted moisture/instability/shear combination which will be in place across the target area, and given the extremely high EHI and SRH values depicted by the WRF along the dryline and in/of the dryline/warm front intersection, I think there is a good possibility of a few strong tornadoes across western NE/far northeastern CO/northwestern KS, especially in the early evening hours as the LLJ kicks in.


I'm not gonna lie, Thursday's potential has me extremely excited.
A potentially significant, chaseable tornado outbreak in my own High Plains backyard? Oh yeah, baby!

EDIT: Mike, excellent observation - this setup does indeed bear more than a passing resemblance to the March 28, 2007 outbreak. Same general area, very similar setup with deep, powerful trough emerging from the Rockies and the dryline draped across far eastern CO and then arcing back northwestward into the NE Panhandle.
As such, my tentative preliminary target for Thursday is Big Springs, NE - that way I can head west on I-80 to intercept any potential convection that fires in the Cheyenne/Scottsbluff area, or head east on I-80 to Ogallala and drop south on Highway 61 towards Grant and Imperial if need be.