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2014-04-02 FCST: KS / OK

Wednesday may end up being a "day before the day of" event, but does suggest some promise in it's own right and is now within the purview of the NAM, so let's kick off a forecast discussion, shall we?

In the big picture, first thing I noticed is it looks like a pretty good fetch of moisture up through the south/central plains. There's a sprawling high pressure centered just off the southeast Atlantic coast, so this air looks to be a lot more juicy than last week's tepid setup. NAM is currently suggesting around 65 tds advecting up through Oklahoma into Kansas. For once so far this season, the heat (theta-e) looks decent too. In the upper levels, looks like a 300mb jet streak of > 100 kts. rounding the base of a western trough and ejecting across the 4 corners. 500mb flow out of the WSW and 850mb flow out of the SSW indicates a decent crossover with height.

At the lower levels, perhaps the most prominent feature is a very sharp classical dry line extending down from a low pressure centered over SW Kansas. Instability looks nice, with ~ 2,500 j/kg indicated just out ahead of the dry line. Also, the temperature gradients and wind barbs suggest a warm front extending eastward from the surface low.

The cap may or may not be an issue. 700mb temps look to be around 5 degrees centigrade.

It's probably too soon for targeting, as that will depend on the latitude of where that lee low sets up. But, for now, south central Kansas and north central Oklahoma are worth keeping an eye on.
 
Wednesday may end up being a "day before the day of" event, but does suggest some promise in it's own right and is now within the purview of the NAM, so let's kick off a forecast discussion, shall we?

In the big picture, first thing I noticed is it looks like a pretty good fetch of moisture up through the south/central plains. There's a sprawling high pressure centered just off the southeast Atlantic coast, so this air looks to be a lot more juicy than last week's tepid setup. NAM is currently suggesting around 65 tds advecting up through Oklahoma into Kansas. For once so far this season, the heat (theta-e) looks decent too. In the upper levels, looks like a 300mb jet streak of > 100 kts. rounding the base of a western trough and ejecting across the 4 corners. 500mb flow out of the WSW and 850mb flow out of the SSW indicates a decent crossover with height.

At the lower levels, perhaps the most prominent feature is a very sharp classical dry line extending down from a low pressure centered over SW Kansas. Instability looks nice, with ~ 2,500 j/kg indicated just out ahead of the dry line. Also, the temperature gradients and wind barbs suggest a warm front extending eastward from the surface low.

The cap may or may not be an issue. 700mb temps look to be around 5 degrees centigrade.

It's probably too soon for targeting, as that will depend on the latitude of where that lee low sets up. But, for now, south central Kansas and north central Oklahoma are worth keeping an eye on.

I don't really have much to add, and agree with your assessment. It's nice to see abundant moisture and instability forecasted. Dewpoints in the mid 60's and CAPE in excess of 2,500 J/kg is definitely nice to see. There does appear to be a warm front running from extreme northern MO into northwestern and central KS. Speed shear and directional shear appear to be nice as well. There is a nice 850mb flow of 35kts underneath 50kts at 500 mb and around 80kts at 250mb. Hopefully the 12z NAM from this morning verifies. I agree this should be the "day before the day", but I am impressed so far with what is forecasted. Definitely looks like a two day event, and possibly three if you include Tuesday, but those days are better reserved for their own discussion thread. Too early for a target like you said, but appears to be a southern KS, northern OK, and central OK event, possibly even southern OK if there are no capping issues.
 
I feel like I keep hearing about how the low level winds, specifically the 850s are going to be an issue on wed. and thur. But I'm just not seeing that on only of the runs. Looks like decent shear to me.
 
Sounds like there very well may be capping issues, and with the sun setting before 8:00, convection might be around or after dark. Possibly a good lightning show, though.
 
It's probably too soon for targeting, as that will depend on the latitude of where that lee low sets up. But, for now, south central Kansas and north central Oklahoma are worth keeping an eye on.

Northern Oklahoma has been looking particularly nasty on the past few runs just south of the triple point. Deep-layer shear above 45 knots with a pretty decent amount of ESRH in place from 0-3 km going into 21-00Z. Boundary layer cooling heading into the evening doesn't appear it will be a problem like it will the day before with the strength of the LLJ and the overall thermodynamic environment. This is looking like a classic N OK/S KS dryline supercell day with storms going well into the evening if everything plays out like it has been.
 
The 850s are looking somewhat weak in all of today's NAM runs. Looks like 25-30kt seems to be in order. Of course I'd like to see them a lot more out of the SE, but then again I'm used to how things work on the Caprock. The latest run of the NAM is draping that warm front right over OKC and goes up roughly I-44. I didn't want to see this that far to the east because that area east of 35 is difficult to chase in. The GFS is still holding hope, however, of the triple point more to the north and west (roughly Enid). Regardless I do believe supercells will exist on Wednesday, but the models haven't nailed down where at exactly.
 
NAM is more south and east with the surface features, as there will likely be a nuisance front with typical early season cold air lurking to its north attempting to barge its way into Oklahoma, however the persistent low pressure to the west seems to be fighting back and helping to keep it at bay. GFS is farther north with the surface features and TP. I think the NAM has a better handle on this as it is more in tune with those finer mesoscale features than the GFS.

I like the overall evolution and placement on the GFS though, so Ill be rooting for that. All models have capping concerns, especially the GFS. Its never a good thing to see the CINH fill in so rapidly around sunset. Too many times you end up with turkey towers that just start to get going around 6pm only to be choked off as the sun goes down by the increasing CINH. One thing working in our favor though is the forecast strong instability. 3000 j/kg is pretty significant for early April, and that might just be able to pop the cap earlier in the day, and with such favorable shear parameters in place (despite some less than favorable 850s) storms could be nice and isolated and very chaseable.

Given the day before is a potential chase, as well as the day after. It seems foolish to ignore the potential here. Time to gear up for the first plains run of 2014. Gentlemen, start your engines!
 
If I lived in the area, I would probably plan on chasing. However, this setup is defintiely not worth driving a long distance for me. I was more impressed a few days ago with the models. While 2500+ CAPE will ahead of the dryline, low-level shear is modest due to weaker 850 mb winds. The other thing I am seeing for Wednesday evening is 500 winds weaken across the plains ahead of the main shortwave. So, your forcing is weakening during the evening hours, you have a cap to worry about, and low-level winds are not that impressive. Plus, since it's still early in the season, you have to hope things pop before 7 PM if you want to see anything. Not a bad setup for the first week of April, but I am going to hold onto my PTO and money for warmer, sunnier, and later setups.
 
Well, now that the NAM is showing some decent run-to-run consistency, it's time to start thinking about some preliminary targeting. Although the latitude of that surface low has still been bobbling around, it seems to be hanging back and hanging tough. So, I'm going to go ahead and call that front a warm front (even though SPC is still referring to it as a stationary front.) There is a pronounced dry line bulge in north central Oklahoma, probably reach somewhere around Enid by 00z. Moisture and instability continue to look good just east of the dry line - you could even call it ideal.

So, where will convection initiate? Right now I'm thinking Alfalfa and Grant county, Oklahoma and Harper, Kingman, Sumner county, Kansas. The lid strength index is weaker there and hanging around just northeast of the dry line bulge is often a good bet. After initiation, I think the warm front will serve as the main boundary for the storms to latch onto. And I love the good-looking low level helicity suggested by the models. I could see a general path up along the Kansas Turnpike or perhaps a little more south towards southeast Kansas as the evening progresses. I realize it's dangerous to focus in too much on bullseyes, but you have to admit some of the severe parameters around Wichita are eye-catching.

Would love to here from others as I think this setup looks too legitimate to ignore.
 
Too legitimate to ignore, indeed, especially when your target hour is within two hour's drive. I really like south-central to southeast Kansas on this one. However, there are some issues. The first being that most upper-level forcing is displaced well west of any target area, although 500 mb shows up to 60 kts in some areas. The second is low-level shear. Helicity doesn't look particularly impressive ahead of the cold front, and speed shear isn't great either. I'd like to see more than 30 kts of 850 mb flow. East of Wichita, however, 0-1km Helicity values are ~150 m^2/s^2 and capping doesn't seem to be as much of an issue there. In fact, I don't see much of a cap there from 4 pm through 10 pm, and the NAM even has cells initiating around the Emporia, KS area.

This hodograph from east of Wichita at 00z caught my attention:
http://www.twisterdata.com/index.php?sounding.lat=37.4444&sounding.lon=-96.5308&prog=forecast&model=NAM&grid=221&model_yyyy=2014&model_mm=04&model_dd=01&model_init_hh=12&fhour=36&parameter=DPTF&level=2&unit=M_ABOVE_GROUND&maximize=n&mode=singlemap&sounding=n&output=image&view=large&archive=false&sounding=y&sndclick=y

As for initiation, like I said the NAM currently doesn't show much of a cap in the southeast quadrant of Kansas throughout most of the day. I don't think storms will have much of an issue firing off the stationary front that could nudge a bit east during the afternoon. If anything does initiate, they shouldn't be screaming fast storms and they will be in an environment supportive of supercells.

Overall I'm pretty excited about this opportunity to get my feet a little wet tomorrow. I'm not a huge fan of the chase territory down there, but I'll probably set up somewhere between Emporia and Wichita on I-35 and go from there.
 
I've only been monitoring this setup off and on, but my two cents: convection in central OK is really going to rely on a small-scale shortwave that's currently not well-observed to initiate convection. The 850 mb temperature on this evening's KMAF sounding is 23 C, which is going to mean a pretty hefty cap to overcome tomorrow, given no obvious synoptic-scale mid-level ascent to cool it. The northern OK/southern KS target might be slightly better, but still toasty at 850 mb. If I were chasing (which I won't be; other commitments), I'd set up near the triple point and hope that you can get a discrete cell to fire along the warm front. My guess is that the warm front is going to be a mess and the dryline is going to be capped. I'll be monitoring when I can because I have family in Wichita, but not expecting much to worry about.

EDIT: After looking at the 00Z NAM, it appears that the mid-level height falls are probably where the vertical motion (and therefore mid-level cooling) are coming from in the NAM. If that is indeed the case, dryline convection might not be so hard to come by.
 
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Western Oklahoma looks like it might overcome it's little supercell drought soon. RAP mesoanalysis and 12Z H7 charts had a weak impulse over the northern TX PH which is encouraging for an extra boost of lift/diabatic cooling ahead of the dryline later. I've heard qualms about sfc convergence along the dryline, especially with it being near stationary all day, but I'm still encouraged by some of the higher-res stuff that localized moisture convergence coupled with at least modest lift from the approaching trough will maybe get it done.
 
Oy, it's a challenging forecast for today. The 11z and 12z HRRRs have shown a compact wave riding along the frontal boundary (readily seen in the sfc wind field near ICT by 16-17z). The effect of this seems to be significant veering of the low-level winds through morning and into the early afternoon before the winds back by late afternoon(not an unusual diurnal trend, mind you). The effect of this is to mix out the boundary-layer moisture -- the 11z HRRR, for examples, has the 60 F isodrosotherm essentially along I44 at 20z, with Tds mixing out into the 40s farther north. In addition, it seems to drive the sfc front southward a bit in northwestern OK. Again, this reverses course by late afternoon and early evening, but the sfc pattern forecast by the HRRR would tell me to get to southeastern KS to stay ahead of the frontal wave. I don't want to trek to southeastern KS on a day with questionable initiation (amongst other reasons), so I set my sights back towards the dryline.

The 12z RAP is showing a very similar evolution to the sfc flow today, although it mixes the BL considerably more deeply (with >90 F temps in north-central OK later today). Importantly, though, it too shows a frontal wave moving along the OK/KS border through mid-afternoon. I have no idea what the real impact this will have on low-level Tds, but I can't imagine it'll be favorable. The forecast of the sfc front lifting rather rapidly northward after 22-23 UTC likely will remove that feature as a source for strong sfc convergence.

12z NAM shows WSW 850 mb flow until ~21 Z. Yuck! Shear profiles are forecast to improve rapidly as we approach 00z (again, this is pretty common), but I have no idea what the storm(s), if any exist, will look like given depleted near-sfc moisture from deep mixing this morning and early afternoon.

My current plan is to hang around OKC, but I suspect I'll head north or northwestward at some point... Everything looks to be about 6-12 hours too slow today (i.e., I'd rather see the 9-12 z forecast for tomorrow at 21-0z instead).
 
Amateur observations

RAP 13Z run... makes the Kansas shear not seem as promising until into the evening hours.. To me it seems as SE KS will not be discrete cells. Best play may be I44 mid afternoon in OKC following to Joplin by nightfall.
 
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