2012-05-23 FCST: KS/NEB/CO/IA/SD/MN

[Ian Miller]

With the advancing low in north west Kansas aiding the moisture return to the central
plains and current dews at 55 to 60 in the corridor between the dryline and the high to the east
the strong LLJ would bring the points up by afternoon and provide the frontal lifting with
enough to work with,south central Neb would be first call if the frontal bondries keep
tracking east and dont stall out.

 

[Jesse Risley]

The 12z suite of RAOB data, along with surface observations, do show that the deepest moisture is well south of the Red River Valley. Between daytime mixing issues and the current (southerly) placement of the deeper moisture, I do think more shallow moisture profiles will be somewhat of a limiting factor in today's setup.

However, of note is the strength of the surface low, which is currently sitting at 992 mb, yet is forecast to deepen a bit to 988 mb late evening, along with backed surface winds in relationship to the surface frontal boundary. It does appear that forcing for ascent associated with the mid-level perturbation should promulgate convective development this afternoon ahead of the surface low/frontal boundary, with CINH also eroding after 20z.

Forecast RAP Skew-t profiles across parts of NC KS and NE (and points E/NE) are progging the evolution of steep lapse rates, notable hydrolapses and WB0 levels around 600-700 mb, with notable T/Td spreads as well. Consequently, large hail, some significant, and damaging winds appear to be the primary threats. However, of particular note is the region of backed winds in the warm sector, which should enhance streamwise vorticity in the PBL such that, despite higher LCLs, a slightly enhanced tornado threat could evolve, particularly just upstream of the triple point and also along the slower moving frontal boundary, as storms may initially remain discrete before congealing into clusters and lines.

 

[Bill Hark]

I am currently sitting in Kearney and am not in a big hurryto leave as I check data. I think there is a decent chance of some nice supercells and possiblytornadoes early in storm development. There is decent SW flow at the 500 mblevel of 40-50 through Nebraska as the day progresses. The dewpoints are stilla little low (50’s) and I am hoping they will improve. I am also concernedabout some potential veering of surface winds as the day progresses except insoutheast Nebraska and eventually storms being undercut by the approachingfront. The 13Z RAP has an area of precip by 22Z extending to near Grand Islandand slowly shifting eastward while the NAM shows the precip extending just pastthe Kansas border, maybe just west of Concordia. I am awaiting the 12Z WRF butthe 00Z init shows a nice area of precip on the Nebraska-Kansas border. Unlessanything changes, I’ll probably head to Hastings and eventually wait in RedCloud.

Bill Hark

 

[JamesCaruso]

2012-05-23 FCST: CO

Having just arrived in Denver last night to start my chase-cation, I am leaning toward taking my chances for a pleasant surprise in northeastern CO rather than drive 6 or 7 hours to northcentral KS / southcentral NEB. If KS/NEB were the only game in town I would go for it, but I am not sure it is worth the drive if there is another option, albeit marginal, close by. Being on my own today without a chase partner to share the long drive also plays into this decision.

Although there may be supercellular structures in KS/NEB, I believe they are likely to be embedded and not at all discrete, with the 500MB flow parallel to the boundary. There will be good CAPE but in a relatively narrow band. Just don't like the idea of chasing cold front setups, and staying southwest closer to the low / triple point is going to be under a stronger cap.

In CO, moisture will be at a premium but as we all know things can happen in CO with much lower dewpoints. Shear could be quite strong, with northeast upslope winds overtopped by southwest flow and the region will be closer to the jet max coming over the Rockies so there should be some stronger forcing for ascent. The NAM shows some nice 3KM EHI over the region, and actually breaks out more convective precip over northeastern CO compared to the areas of interest in KS/NEB. The Denver AFD seems relatively optimistic about the potential for severe weather, particularly for Douglas, Elbert, and Lincoln counties, and even mentions a tornado threat.

I will be targeting Limon initially and watching for development in the region just south of I-70, depending on where the frontal boundary sets up. While I'm waiting, I will be anxiously eyeing the situation in KS/NEB to see what I'm missing

Jim Caruso

 

[Timothy Finn]

With the combination of the forcing feature, the CAPE value, the moisture, and EHI values, I'm pretty happy with the possibility of a SC NE event. My only concern is if the cap will erode as forecast, but still, I like it enough to go chase it. Thinking action will be between Phillipsburg, KS, and Geneva, NE. Probably going to stage in Hebron, NE

Tim

 

[TrumanBoyer]

For whatever its worth -- to those of you playing close to the triple point.

I've found that you need to stay where there are strong SE surface winds.
Its easy to get into a SW flow if you get distracted by a good looking storm.

If you get in the zone where winds are the slightest bit westerly, jog a bit farther
East and/or North, sometimes 30-40 miles makes all the difference in the world
with a tight low.

I'm sitting in Maryland playing armchair quarterback. Had to leave the Plains early.

Get some for me. I am calling for SE Nebraska - I think Hebron looks like best shot.

-Truman

 

[Dean Baron]

I think the tornado threat is minimal at best today. Temperature-dew point spreads are 25+ degrees in Nebraska and northern Kansas and that will probably only get worse with daytime heating. You are going to have a helluva time getting a tornado in that kind of environment. On top of that, at least for the northern end of the setup in eastern NE/western IA, it looks like storms will fire behind the front. Not that you can't get decent storms out of a setup like that, but combined with limited moisture and high LCL's, I don't see this being a big storm day unless a storm can locally enhance its own environment.

 

[JamesCaruso]

Situation in northeast CO not looking as good based on obs, updated DEN AFD, and SPC 20Z outlook. Sitting tight in hotel lobby near Denver Airport, keeping an eye on obs and radar. Some convection beginning off the foothills so will hold out hope for something. This is the first day of my chase vacation so anxious to get out onto the Plains. Not feeling in "chase mode" quite yet, being in the outskirts of Denver and spending most of the day working to kill time when not analyzing weather data!

Situation in NEB doesn't look much better, so I'm at least feeling better about my decision not to drive 7 hours there today.