04/05/05: FCST: Central Plains/Upper Mississippi Valley

[JHadorn]

I will be playing southeast Nebraska today, mainly Gage County due to my having to work today and getting off after the likely 2:00 PMish initiation time. My hopes for southeast Nebraska are elevated today as the RUC is forecasting a tongue of 60 tds to be in my area, surface CAPE of approx. 1000 - 2000 j/kg, and LI of around -3.

My main concerns right now are the likely strong inversion that will be in place, the lack of any real backing winds, the low helicity, and I'm slightly concerned that moisture may be mixed out.

Surface temps are forecasted to reach the 70+ mark, so hopefully that will help negate some of that inversion.

 

[Philip Flory]

Target area for this afternoon is Great Bend, KS. Window of possiblility of tornadogenesis does not appear to be very long however. Am looking for initiation by early afternoon NE of the SFC low currently west of DDC.

Am not impressed enough with the SE/E OK oppurtunity to warrant a trip down there, also factoring in forecast storm speeds/terrain. I do agree with SPC a couple isolated supercells are quite likely, especially first 2 hrs.

Best of luck to everyone heading out today!

 

[Tony Laubach]

Good morning again from Pratt, Kansas where the current temp/dewpoint is 57 over 54 with 14mph winds coming out of the southeast. I just got off the phone with Mike's Auto in regards to our car; we're expecting to hear back from them in the next 15 to 20 minutes in regards to the car, so hopefully that means we should be on our way. This would serve nicely so I could go back to bed! )

Early check of the forecasts seems to indicate us being in a good place. We're probably gonna stay to the northeast of the SFC low and hopefully have good position as storms fire. I imagine the window of opportunity for tornatic activity is going to be rather small, so we're going to try and get on storms on initiation. The vorticity associated with the low coming across southern Kansas will make up for the lack of shear and probably give us a chance for a couple small, short-lived tornadoes before storms congeal into a nasty blob. Moisture is already doing well with current Tds in the mid 50s, so hopefully on S/SE winds, the moisture can continue to increase a bit. Instability will be in good form with estimated CAPEs in the 1500-2000J/kg with temps closing in on 70. Right now, looking outside, I'm being blinded by the sun, so we're sitting in some clearing. Satellite right now indicating a stream of clouds all around us.

HWOs and AFDs over DDC are indicating this best chance lying northeast of a line from Ness City back towards Pratt, so I imagine any moving we do today will consist of us following a path right along that line. We have to be quick to be in position as these storms will fire quick and early and quickly congeal into a blobby mess, which will likely reduce the tornado threat and leave us sitting in the hail.

It's going to be a narrow window which I think we're in good position for; its just a matter of being in the right place in that narrow window we do get. I'm sure we're going to see some hail and maybe a couple weak, short-lived tornadoes. Initially, we're going to position ourselves east/northeast of the SFC low on a hill somewhere and wait for storms to start firing, probably moving in at them from the west.

This all assuming we can fix my car in time! ;o)

 

[Shane Adams]

Current 21Z & 0Z RUC models paint an interesting picture, with isolated precip forecast to breakout between 18-21Z in S/SC Oklahoma. What's interesting about this feature is that it doesn't move east much at all by the 0Z run. Now the question is, is the RUC out to lunch or is it picking up on a slowing trend regarding the LOW in SW Kansas? RUC also shows more favorable instability environment than the ETA (NAM), with 2500 CAPE values as far north as EC OK by 0Z. Perhaps the RUC is being over-zealous, but regardless, my target (per late night ETA analysis) is the Red River Valley area, bounded on the north by the Ardmore/Durant/eventually Hugo US70 corridor, and by the south along the Gainseville/Bonham/eventually Paris US 82 corridor.

Vertical shear is much more favorable for supercells in this area, the 500mb winds arc more SWerly than they do further north, closer to the LOW. Better fetch of moisture, slightly higher surface temps (hopefully), plus the aformentioned CAPE all point to this area IMO. Intiation looks to be in the 19-20Z range, and with semi-decent chase country in the target area, seems a good chance at an isolated supercell with room to move along, at least during the first few hours of initiation. Another plus is good NOAA coverage in this region. Most-likely be heading out the door in a few hours, to begin somewhere east of Ardmore.

 

[Karen Politte]

Fairly homogeneous airmass in place from Austin to ICT this morning. Dewpoints acorss this whole region ranging from 55oF to 61oF or so - give or take a few degrees. One thing that troubles me is that north and central Texas dewpoints still have 50-somethings mixed in with their 60s.......on the morning of a potential severe weather episode, that doesn't fill me with gallons of hope.

The RUC is having a hard time nosing 60-anything degree dewpoints past Paris, TX until around 0Z, when it finally manages to get them over the border near Idabel or Broken Bow, OK. However - I'm wondering if it might be under-doing moisture, as looking right now I see that places around Ardmore, OK are reporting current dewpoints of around 60-61oF.

Dryline is currently in Oklahoma around Weatherford, with good veering/drying behind it.

The CAPE axis seems to get sucked up I-35 until around noon, and then it gets shunted east with the dryline. It DOES try to wrap CAPE signature around the low in SW KS/NW OK by 0Z - but whether this will be sufficient for any 'real' fireworks or not is still anybody's guess.

There has been a lot of optimism about the length of time we have had return flow with this coming system - but what people seem to have overlooked is the fact that the Gulf can suck and suck and suck until it's blue in the face at this time of year.......that doesn't mean that we will be having quality moisture return. It's all relative - and has to be put into perspective with the previous beatings that the GoM has suffered over the past 2 or 3 weeks.

Rather than hope for last-minute-miracles, I'd rather bide my time and wait for long-term pattern change. Like May.

I guess that's why I'm not chasing today.

KR

 

[Jeff Snyder]

Agree with Shane... I started to write up my post, but realized that it would be merely a combination of my previous posts and what Shane wrote in the above post. I have a hunch that we'll see a semi chaser-convergence along Hwy 70 in OK (Ardmore to Durant to Hugo) or Hwy 82 (Gainesville to Sherman to Bonham to Paris), seeing how those are the only two main routes east of I35 if you want to stay out of the Dallas metro area (meaning stay north of Hwy 380 and I30).

At any rate, the 12z soundings from OUN and FWD (and SHV and DDC for that matter) show a very impressive elevated mixed layer (EML), which I like quite a bit. With this type of situation, you really do see either boom or bust, since the dry adiabatic lapse rates evident on the soundings from ~850mb to ~500mb (and nearly dry adiabatic from 500mb to the trop.) make for awesome instability potential (assuming you can get sufficient surface T and Td). On the other hand, it also means a very stout cap, which can put a dagger in initiation attempts. All models have shown that Cinh will become negligible by mid-late afternoon, so I'm hoping for the former...

 

[Mike Hollingshead]

However - I'm wondering if it might be under-doing moisture, as looking right now I see that places around Ardmore, OK are reporting current dewpoints of around 60-61oF.

With the shallow moisture you mention after this, you will likely see many of these morning dews mix out once the sun starts working on them. I try not to put much stock in morning dew obs when you know the gulf is likely not 'restocked' yet.

 

[Glen Romine]

However - I'm wondering if it might be under-doing moisture, as looking right now I see that places around Ardmore, OK are reporting current dewpoints of around 60-61oF.

With the shallow moisture you mention after this, you will likely see many of these morning dews mix out once the sun starts working on them. I try not to put much stock in morning dew obs when you know the gulf is likely not 'restocked' yet.

-

Excellent point Mike - but this is where looking at the regional soundings can offer you some key information to anticipate what is likely to happen. Note that both OUN and DFW show decent low-level moisture - though not particularly deep - but capped by a very stout inversion. Such a stout inversion will greatly limit the amount of vertical mixing and thus should limit the maount of drying. However - the moist layer in both cases shows a decreasing water vapor mixing ratio with height - so dews will lower from deeper mixing - perhaps several degrees from current values. We can also see from these sounding that winds are likely to veer with mixing to around 190. Further west - the MAF sounding shows a very shallow inversion and 50 knot westerly winds just off the deck - so expect a very rapid moving surface boundary, particularly near the Red River. RUC forecasts of the dryline reaching the I-35 corridor by 18Z looks quite feasible.

Glen

 

[Shane Adams]

RUC newest runs still consistent with a slowing trend for today's convection along and north of the Red River. A recent satellite view clearly shows the LOW retrograding SW slightly, which would seem to indicate the RUC solution is closer to "true" than the current ETA solution. Windfields look great for supercells, and dews continue to slowly rise. Yes, I'm well-aware of the mixing and tainted nature of the current Gulf air, but it's April so I'm expecting it.

One fly in the ointment is the veering of surface winds gradually eastward, but the moisture continues to build and rotating storms are a sure bet, given the h85-h5 windfields in place, be they tornadic or not. If storms can develop right on the windshift line currently in EC OK generally east of 35, I think local enhancement of backed flow can be a possibility for any significant isolated supercell. At any rate, it's the best we have to deal with today.

Worst case, I think we'll get a nice sup with photgenic qualities. A consolation prize perhaps, but with the magic of mesoscale, anything is possible. So why not? We're out the door....

 

[Karen Politte]

The dryline has mixed east of Norman. We have lost our racing strato-cu that we had this morning, and are now as clear as a bell. Our dewpoint is currently 37oF - whereas two counties to our east the dewpoints around Seminole county are in the 60's.

KS targets look rather impotent right now. I suspect that a line will develop fairly quickly in eastern Oklahoma - so you'll need to be on stuff out there as it goes up and try and keep up with it until that line does form.

I'm surprised there's not more talk about the NE TX target - where there could possibly be a tail-end-charlie.

It will be interesting watching what happens today - but I'd rather be watching it from the office than out on the road spending all that gas money which I'd rather have for May.

KR

 

[Karen Politte]

Also - I'm suspecting that Mena, AR's dewpoint is in error - as it reads 68oF. Considering that there are not any 68oF dewpoints in Texas - even along the Gulf coast - or in Louisiana.......I would regard that ob as highly suspect.

KR

 

[Glen Romine]

Signs of new convective development just ahead of the dryline surge in southcentral KS (northern Kingman County). Surface conditions there are in the low 70's with mid 50's dewpoints, just north of a weak sfc trough aiding in somewhat backed winds from about 160@10. Overhead, SPC mesoanalyses suggests strong diveregence overspreading the region combined with cooling at 700 mb. Could see SPC finally issue a watch in this area with increasing coverage of potentially sfc based convection. Farther NW, deep layer shear may not be adequate for sustained updrafts, and cloud bases will be higher, but nevertheless vigorous convection there has been occassionally triggering the shear algorithms.

edit:

Ok, new watch out. SPC has gone with a svr for KS.

http://kamala.cod.edu/offs/KWNS/0504051903.wwus20.html

Also a new MCD out as well, suggesting potentially rapid southward development ahead of the line - primary mode rapidly becoming linear.

http://kamala.cod.edu/offs/KWNS/0504051858.acus11.html

edit 2 (~2:25 CST):
Another SVR watch issued by SPC covering much of OK and parts of AR,KS and MO for the rapidly developing line of convection east of the dryline. Southern extent, based on vis sat, will likely extend at least to the DFW metroplex, so additional watches may be needed. Further, the availability of mid 60's dews shear oriented more perpindicular to the forcing in that region may improve odds of more discrete convection. Additionally, the persistent cloud cover over ne TX is starting to slide east which may allow for some reduction in the large CINH over that area. Based on the obs just ahead of the dryline - temps will need to warm at least 7-8 degrees to allow for sfc based convection further east. Seeing now that SPC is issueing a tornado watch for portions of AR OK TX - in agreement with the above assessment.

Glen

 

[Karen Politte]

Dryline has already lit up extensively and surprisingly quickly about 50 miles east of OUN, in a line extending north to south through the whole state. For those chasing, this may be bad news - forcing/mode appears to be favoring linear already.

Square severe thunderstorm watch issued for ne'rn quadrant of OK.

KR

EDIT: Line of storms is visible from downtown Norman - I just stepped out to sweep the sidewalk in front of my office after having seen the wall of convection to my east and southeast out of my large (nice!) office windows which face that way. Convection appears "average" right now but it's early. Looks like a pretty solid line with no one cell really taking the initiative yet. On radar - storm over the Canadian River around Byng Oklahoma looks to be the most intense as of now.

 

[Mickey Ptak]

Also a new MCD out as well, suggesting potentially rapid southward development ahead of the line - primary mode rapidly becoming linear.


Glen

That is becoming very apparent here in OKC. I was going to leave and head east here shortly, but the line of CU are becoming linear as I write this. So I may change my mind.

Mick

 

[Glen Romine]

That is becoming very apparent here in OKC. I was going to leave and head east here shortly, but the line of CU are becoming linear as I write this. So I may change my mind.

Mick

It could be tough to catch. Local dryline surge west of more vigorous cell in Pontotoc County could aid that cell to further intensify in the short term - and there is somewhat of a gap to the south if it survives a few short term mergers with lessor cells. Doubt many folks will be in Hughes county to greet it - but it could look pretty good by then.

Glen