5/21/07 FCST: SD/NEB/CO/KS/OK/TX

[Ray Walker]

Monday looks interesting for much of the High plains and parts of nebraska. However I am having a hard time picking a target thanks to the mid and upper level wind feilds being farily weak over a large area. Instability is lower the further north you go, but wind feilds are better, and instability is higher the further south you go but wind feilds are much weaker. Right now I would thing Dodge city Kansas is a good starting point.

 

[Justin Turcotte]

Just took at look at the 06z NAM which now looks more like the 00z GFS and GEM in terms of boundary location and QPF placement. Shortwave moves through the Dakotas during the day. NAM 925mb wind exceeding 30 kts so 15-25 kt south/southeasterly surface winds likely in the Northern Plains. This combined with solid southwesterly midlevel flow should produce some nice looking hodographs. Moisture return not real juicy up north but recent rains in Dakotas along with more rain possible before this system should aid evapo-trans and dews in the low to mid 60s not out of the question. NAM is already spewing out EHI values in the 3-4 range over the Dakotas. Cap is not very strong in Dakotas so seeing a storm should not be a problem. What may be a problem is getting a lot of cells popping up early and fairly quickly which may leave a small tornado window. Looks like a stormy afternoon in eastern ND, central/southwest SD, and the NE panhandle. Further south, a stout 600 mb shortwave and associated mid-level speed max could lead to some robust supercells along the dryline in the TX panhandle.

 

[Kurt Hulst]

I only have one day to chase this week and I am sitting in shamrock, TX My target for tomorrow is for the area around Amarillo, TX. I am anticipating on playing the dry line. It shows a weak disturbance coming through. possible Ofbs from this evening storms might bring some nice interactions. 12z Skewt for AMA was showing nice LCLS as well near 850mb. I might post something tomorrow. The effective shear is reasonable coming upon the 21-00z hours based off the 18z run NAM.

Edit: Now looking at the 00z.

Still looks reasonable but it places the dry line west of AMA a bit further than it did. NAM shows a pocket of 40-50 Effective Shear. Cape 1000-1500, and small areas of 2,000 J/kg. Dew points in the upper 50's with a few hopeful areas of lower 60's The LLJ strengths around 21-00z in northern Pan Handle. There is not much upper level support above 500mb.
However i wouldnt be supprised to see this area in atleast a 5% tor tomorrow.

Well I have a long drive a head of me tomorrow as i need to head home after the chase, so i am going to get some rest.

 

[Mike Hollingshead]

I was thinking nw SD, but am now starting to lean to simply going to western NE and hoping for something very deviant out there(to help with the crappy mid-upper level flow). The general area just loves to have those kind of surprises for a person when they don't bother heading out, and I guess I figure the chance is there.

 

[Bill Schintler]

Chase target for Monday, May 21

North chase target: Mobridge, SD
South chase target: Wakeeney, KS

Synopsis:
At the upper-levels, the WRN CONUS trough will continue to amplify Monday while too the south of the main flow a number of compact pieces of energy will translate from W to E across the SRN and SWRN states and Mexico. In the NERN US, the closed low will weaken and move off to the NE as ridging builds in the SERN US into the Great Lakes. At the SFC, low pressure will strengthen along a N/S oriented CF in response to forcing from the upper-level flow in WRN SD while a secondary low will begin to form in WRN KS late in the period. A DL will also become established to the S of the developing KS low during the afternoon hours.

Discussion – north target:
Gulf moisture, with dewpoints into the low 60s, will surge NWRD with the aid of a 35kt H85 LLJ. Further north from NEB into ND, similarly high SFC dewpoints will develop primarily from evapotranspiration. Steep lapse rates; as noted on RIW, SLC, DNR, and GJT soundings; will advect EWRD over this moisture in NEB and SD and contribute to MLCAPEs in excess of 2000J/kg to the E of the northern low. In this area, a strengthening and veering 45kt LLJ over backing SFC flow will increase directional shear. A significant negative may be that the ULVL forcing and strongest H5 flow might be well to the west of the instability axis throughout the daytime hours. However, a narrow axis of veering 35kt H7 winds above backing SFC flow may result in sufficient speed shear for storm organization. Overnight, A strengthening LLJ should aid in the maintenance of one or more MCSs which will track E across the Dakotas.

Discussion – south target:
Models continue to advertise a compact, elongated S/WV well S of the main ULVL flow which should move into WRN KS during the afternoon hours. This feature, in combination with convergence along the aforementioned developing SRN low and dryline in addition to strong SFC heating, should result in SFC-based convection during the mid-afternoon hours. A potential negative is that this wave may move through the area too early in the period, followed by subsidence and warming mid-levels with H7 temperatures increasing to nearly 10C by early evening. Hodographs will be impressive as 35kt SWRLY H7 flow surges over increasingly backed 20kt SFC flow.

[FONT=&quot]- bill [/FONT]

 

[Angie Norris]

Haven't had much time to work on any detailed analysis, but I'm leaning towards the AMA area as well. Did notice a small OFB a bit ago near the Borger area, so that may provide a nice little focus for later this afternoon. It does concern me that the dryline looks like it will hang back near the NM/TX border...I really don't want to be that far west, but we'll see later today.
Preliminary target...Pampa. Hope to finally see a forecast verify through my viewfinder instead of watching on TV.

 

[Wesley Luginbyhl]

Considering I have a 5% tornado over my house for tomorrow, hopefully my drive may be limited to a few counties for the first time this year. The dryline looks to hold back by the WRF, but the GFS has it sitting on my house here in Borger (I prefer the GFS in this case). If you go by the WRF though, the 3km helicity looks to have a bulleyes on AMA with values over 450. CAPE is a little low for my taste according to the WRF, but if it is clear like sunday was I would expect widespread 2000+ CAPE valves all over the panhandle. Its a shame the upper level winds are a few days out, because the low level winds look to be rockin tomorrow.

A weak line of storms rolled up through the central panhandle overnight. I was gonna get some lightning pictures but they completely fell apart around midnight. If this left behind some boundaries, it may help set up something later today. With the season the Panhandle is having, I dont think I would want a storm anywhere near my house, even if it is just marginal day at best.

 

[Ilya Neyman]

I agree Wes!

12z NAM looking more impressive for today throughout the board, not only has it increased 850 winds further (now 35-40kt by 00z) but is now advertising the dryline to surge eastward vs. the stationary axis near the TX/NM line it was depicting before. There are currently 2 DL bulges to consider per the NAM - one pushing across the OK panhandle and into far SW KS...and another one across the SW TX panhandle around the vicinity of Lubbock. Furthermore, the fcst precip. fields look more promising for discrete supercells up and down the panhandle by late this afternoon/evening (I believe this is a combination of the factors discussed previously). Gotta like the helicity, moisture and the winds with this one. Also 300mb flow is progged up to 30kts (big difference from 5-15 it was depicting just a couple days earlier). Will this pan out? I guess only time will tell but in my opinion it is definitely worth going out for, keeping in mind that panhandle elevation does do things sometimes! Anyway, Curtis McDonald, Matthew Chatelain, Eddie Natenberg and myself are gearing up to head out, with the preliminary target being somewhere in the central part of the Panhandle at this time and open for reassesment later this afternoon. Also, we are looking into getting into position for tomorrow's setup as well.

Good luck to all chasers out!