2015-03-25 EVENT: TX/OK/AR/MO/IL/IN

MODS: Add states as needed.

Looks like the midwest could see its first round of severe storms Wednesday evening and overnight. Not looking like a big tornado threat at all but the GFS does show CAPE up to 1500 ahead of a southward advancing cold front with 60s tds ahead of it. Speed shear and forcing along the front seem more than adequate to get a linear complex of storms going.

Timing looks to be an issue as things look like they could light up just before dark when instability begins to wane, but with the forcing and shear in place that could be enough to promote a fast moving line of low topped storms capable of damaging winds. Given it is 5 days away I won't look into it more than that at this point.

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Too bad that depicted surface low isn't sitting about 500 miles off to the southwest instead of the upper Lower. Still, liking any potential at this point..
 
Is it sad that I will be happy for a rumble of thunder out of this? That's probably the most it will amount to at this point, anyway. Just can't see the instability getting in place here in time for much.

Naturally I hope I'm wrong.
 
Is it sad that I will be happy for a rumble of thunder out of this? That's probably the most it will amount to at this point, anyway. Just can't see the instability getting in place here in time for much.

Naturally I hope I'm wrong.
Interesting point you brought up, I had to look it up locally here in Detroit. The last time we had a thunderstorm was October 28th, almost 5 months ago. That in of itself is quite a streak.
 
MODS: Please add Oklahoma to the thread title.

Very, very interesting scenario unfolding on the latest runs of both the Euro and the NAM. The Euro has been gradually shifting the better moisture/lift further west right along and just west of 35. The NAM has been progging extraordinarily high MLCAPE values at or above 3000 j/kg which I'm not totally sure will unfold unless the dewpoints hit the mid-60s before 21Z right before peak heating. The low-level shear really ticked up on the last few runs of all three models (Euro, GFS, NAM) with the dryline being nicely positioned just far enough ahead of the cold front to be a big player for initiation in better terrain/roads back west. I wouldn't be surprised if March finally gets on the board tornado-wise from this.
 
MODS: Please add Oklahoma to the thread title.

Very, very interesting scenario unfolding on the latest runs of both the Euro and the NAM. The Euro has been gradually shifting the better moisture/lift further west right along and just west of 35. The NAM has been progging extraordinarily high MLCAPE values at or above 3000 j/kg which I'm not totally sure will unfold unless the dewpoints hit the mid-60s before 21Z right before peak heating. The low-level shear really ticked up on the last few runs of all three models (Euro, GFS, NAM) with the dryline being nicely positioned just far enough ahead of the cold front to be a big player for initiation in better terrain/roads back west. I wouldn't be surprised if March finally gets on the board tornado-wise from this.
I noticed that too, although it still looks like April 3-5ish will be even more impressive. The models have been really consistent with bringing in an impressive neutral to slightly negative tilt trough in around that time. All the ingredients look like they'll be in place for a decent sized severe weather event. For the models to be that consistent that far out has been enough for me to mark it on my calendar.
 
I am not really expecting too much out of this event in the Chicago metro area besides maybe some heavy rain and large hail. may even hear some thunder tonight (Tuesday). it will be a welcome sound after a winter that just wont end!
 
I am not really expecting too much out of this event in the Chicago metro area besides maybe some heavy rain and large hail.

I'd be willing to drive a few hours for large hail! But honestly - I"m not seeing what you're seeing... I would think that threat is at best into far southern Illinois. But you have my interest :) Whatcha looking at?
 

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NAM is still on the war path for Wednesday with the Euro in relatively close agreement. The GFS maintains a much more progressive front but still a somewhat distinct dryline down around Lawton and back into N Texas. NAM is still running a bit high on moisture just from my perspective, but low 60s well across the Red River looks pretty likely at this point. Forcing for ascent looks like it's gonna extraordinarily strong along the cold front that'll likely be positioned somewhere around El Reno by 00Z and continuing SE. Relatively consistent winds aoa 40 knots from 700-300 mb all day with a trailing impulse at H7 immediately following behind that straight jet that ejects across Kansas today. I'm still foggy on whether or not 3000+ j/kg of MLCAPE will be realized this early in the year, especially if moisture doesn't materialize as progged, but nonetheless it looks favorable coupled with the great turning in the lowest 1 km along the dryline and just east of the 1006 mb sfc cyclone. I'm betting on the northern end of this turning into a QLCS pretty dang quick, probably before 00Z with maybe some trailing supercells down on the northern end of the dryline closer to the sfc cyclone around 22-00Z. Might get lucky and have one rogue storm that spits out a tube.

Tentative Target
: Walters, OK
 
12Z OUN and AMA sounding showing 8.4 and 8.6 lapse rates respectively, and low 60 dews are showing up across southern Oklahoma this morning. I still have a hard time believing the 4000 CAPE advertised by the NAM, but even 2500 wouldn't be bad, especially for March. We'll see how quick the cold front is. If it holds off, we could see discrete dryline supercells. If not, squall line. Either way, it will be nice to have thunderstorms in OK again.

I'm looking forward to getting out for my first chase.
Target: Wichita Falls, TX
 
12Z OUN and AMA sounding showing 8.4 and 8.6 lapse rates respectively, and low 60 dews are showing up across southern Oklahoma this morning. I still have a hard time believing the 4000 CAPE advertised by the NAM, but even 2500 wouldn't be bad, especially for March. We'll see how quick the cold front is. If it holds off, we could see discrete dryline supercells. If not, squall line. Either way, it will be nice to have thunderstorms in OK again.

I'm looking forward to getting out for my first chase.
Target: Wichita Falls, TX

Agreed, the uncertainty was pretty well reflected in the AFDs from DFW and OUN respectively. DFW is thinking the front will hold off long enough for semi-discrete supercells on the northern end of the dryline while OUN is leaning towards the forcing for ascent along the front being too strong. I'm leaning more towards OUN's solution but they've also been very wrong before.
 
I am not feeling particularly optimistic about this setup at all for two reasons. The first is the severe lack of good, deep moisture available. It may be March, but the 12 UTC CRP, BRO, DFW, and OUN soundings don't have me thinking about severe weather. The moisture is shallow and the 16 UTC surface charts only show a few stations across Oklahoma and Texas that have the dew point above 60 F. Surface observations show that the air mass down near Brownsville looks better, but the BRO sounding shows that it's really not that deep of a moist layer. Combine that with the speed the cold front is forecasted to move through Oklahoma, and I become more and more likely to throw out models like the NAM that are advertising large CAPE values and nice supercell environments. In addition, I can only see one or two high-based supercells developing out ahead of the cold front only if they can develop via splitting early enough and fast enough to develop a right mover that will stay ahead of the front. That might be difficult to achieve given the moisture issues at hand. Having a supercell might be a good show, but it'll be short. Meanwhile, anything else will run straight into the front or develop along the front in a linear fashion. I think it's going to be a small window for any supercell activity, otherwise you'll end up chasing linear storms.
 
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Taking a look at morning data, the 12z observed OUN and SGF soundings + forecast skew-T profiles do show favorable hydrolapses and suitable WBZ/freezing levels to justify the threat of large hail later today. I think there is a small time frame early on this afternoon, namely across central/northeast OK, where the tornado threat will likely be maximized just ahead of the surface low. I'd be watching that theta-E axis in the region of enhanced SRH where, combined with ample CAPE values and a favorable LLJ, if a few discrete storms emerge in the first few hours after initiation there ought to be at least a few tornado reports.

The frontal boundary appears to foster the amalgamation of cells into less discrete structures within a few hours after initiation, and this is supported by short-term convective forecast models. The area proximal to I-35 and south of I-40 appears to be the initial favored zone for discrete storms, possibly extending ENE towards KTUL, especially in vicinity of the effective warm front.
 
I too have looked at the 12z sounding for OUN and its is shaping up to be a stone throwing kind of day. The shear profiles do suggest a chance for a tube or two. The SFC-03km SRH really sticks out along with the backing winds.
 
TARGET: OKC First chase of the new year for me ! PROS: Classic set up of a surface low in OK with warm front and dryline. Should be a triple point around OKC around 7 PM. Ample upper winds with short wave should make for some long anvils. CONS: I don't like some of the veered surface winds on some of the forecast models tonight. Also, strato-cu was not very thick over the Dallas area this morning, so the quality of surface moisture is in question (Rich T: Look at the source region !). Expect mostly hailers. Lots of seeding along the warm front will keep me farther west-southwest. Expect to dive south this evening as storms build toward the Red River.
 
The morning stratus and stratocu have mixed out over much of central and south-central Oklahoma, with clouds hanging tough across northern and much of eastern Oklahoma. The morning model forecasts have been a bit better in terms of keeping winds north of the front a little more veered (i.e., from the east) and delaying the backing of the winds (from east to northeast and, eventually, north) a few hours. As a result, the area north of the front across northeastern Oklahoma and perhaps far southeastern KS, southwestern MO, and northwestern AR looks to have favorable wind profiles for a tornadic threat this afternoon. South of the front, the models are a little less consistent in terms of whether the 2m/10m winds will stay out of the south or veer to southwesterly. Current obs show solid 61-63 F Tds across much of the warm sector in OK, which, with abundant insolation at least across central and south-central Oklahoma, will lead to moderate or high CAPE by this afternoon (2000-3000+ j/kg). Dewpoint depressions will be a little suboptimal for a siggy tor threat, but we'll see how the moisture evolves during the day.

As others have noted, there may be a relatively narrow window of an hour or two for a discrete or semi-discrete supercell to develop or mature near the front, before the front barges southward by very late afternoon and into the evening. If the front can lift into far southeastern KS as a warm front this afternoon, that may not be a bad place to be. Another option is near the triple-point, which the latest 15z HRRR has WSW of OKC by late afternoon. The stronger 850 mb flow will reside east of I35, with better shear profiles likely to be located near the longitude of Tulsa and north of the warm front (at least as long as it remains a warm front before it transitions to a cold front). The 12z 4 km NAM lines out the convection in OK pretty quickly by late afternoon, but the recent HRRRs seem to keep some quasi-discrete convection around for a few hours, particularly in central OK with storms that develop near the dryilne. Since I'm in Norman now, my plan is to hang around and see how the front evolves during the early afternoon. If the winds stay easterly near and north of the front, I may hedge northward (that's closer to home anyway). If the winds back to northeasterly north of the front, I'll hang around here longer.
 
What are folks' thoughts on the ongoing convection up in S. Kansas laying down some boundaries and how that might impact some of the plans for later?

The cloud deck here in central Osage Co. has not yet started to thin and it is still chilly, so it will all depend upon what time the stratus clears whether I get a backyard chase or not. My work-schedule inflicted target is the Pawhuska/Bartlesville cooridor.

Best of luck all.
 
The moisture is pretty thin over Texas per the 12z soundings. Models, particularly RAP, are cratering the dewpoints this afternoon...particularly south of the Red River. I put together a quick image of the Fort Worth, Del Rio and Corpus Christi soundings. I'm staying home today even if a nice storm pops up west of Mineral Wells per the latest HRRR. 30F+ dewpoint depressions and resultant high based cold outflow-dominated storms are something I've chased far too much of the past few years. I'll pass :)

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I'm liking the better-than-forecasted surface dewpoints and wasn't disappointed by the 12Z sounding at OUN. Mesoanalysis is showing an area of faster 500mb winds coming into SW OK here around 1230 and water vapor shows the edge of the shortwave entering the western Texas Panhandle. I think timing should be good for a show this afternoon in Central and Southern Oklahoma.

I'm not liking the SW surface winds along I-44, which is where I was initially hoping to target today. It appears all the backed surface winds are east of I-35. Nevertheless, I still am liking the dryline play today.
 
I'm targeting Minco today at the triple point with the RAP nosing 60 dewpoints just south of I-40 at 22z, although as mentioned the surface winds look to be from the SW more often than not. Another concern for me is trying to keep up and navigate rush hour traffic in OKC and not fall behind. Part of me is hoping it develops a bit to the north so I can avoid the immediate metro area.
 
From my ATL armchair....

I like the END- TUL area based on the latest Mesonet obs, temps north of the front are warming up, T-TD spreads are lower up there and the winds are more backed. HRRR has the best UH signal up there as well. Supercells are likely, at least at first, all the way to the Red River, but to me the best tornado chance seems to be NE Oklahoma right now.
 
I'm not 100% sure what to make of what appears to be some impulse crossing Oklahoma as I type this. A notable mid-level cloud deck has formed and pressed east. As it encroached on the OUN/OKC metro, well defined mammatus could be seen underneath it. There is a dramatic wind burst in the mid levels associated with this feature (wind speeds have increased from upper 30s to near 50 kts as per SPC mesoanalyses over the last 2 hours). There is an appearance of some weak lift from this feature on water vapor satellite, but mesoanalyses and vapor satellite show the main trough is still to the west, generally back into central CO and eastern NM, although winds weaken between the OK feature and the trough axis. I'm a little worried this feature will try to initiate convection before the atmosphere is primed and thus result in a less than impressive main show. Also, there could be subsidence behind it, and shear looks to weaken behind it as well.

For those reasons, I think the area near the warm front across N/NE OK and into SW MO is probably the best place to consider for a tornado play. I'm sure storms will fire along the front to the SW across C/SW OK later this afternoon, but I think a combination of large T/Td spreads and weaker shear will result in a non-supercell mode being favored. Also, the cold front will surge southward faster in this area compared to near the warm front. I have been thinking Stillwater all day, despite the poor chase terrain in the area. Something behind trees is better than nothing if you ask me. I'm just not going anywhere near the OKC metro.
 
The moisture situation (and the related LCL situation) is quite a bit worse than the 2m sfc obs suggest according to the 20z OUN special sounding. Lapse rates in the commonly-used layers look great thanks to the warm 2 m T and cold middle troposphere, but "bleh" to the moisture. The storms that developed to the immediate northeast of OKC a couple hours ago have moved up towards Tulsa with some cylonic shear aloft noted with mesocyclones associated with a couple of the storms, but nothing has yet to develop in the "secondary" area where the HRRR had been forecasting CI W or SW of OKC.

The storms in Osage County look well positioned for a low-level mesocyclone threat in the near term, but it may get slammed by cold outflow from the supercell nearing Tulsa soon.
 

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Here is the 6:40PM KOKC reflectivity of the Moore, OK cell showing quite the wrap-up.
 

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