3/30/06 FCST: IA/NE southward to central TX/LA

I know it is a long way out but it is already getting some media coverage and showing up under SPC experimental outlook.
Looking at GFS models temps in region in the 70's with dewpoints 60-70 with a strong surface flow from the south sucking Gulf moisture well north. Higher level winds are screaming and veering more to west in front of the approaching front. All this is anchored by a slow moving giant Low in the Dakotas.
At this point it is far enough out to plan to chase - will follow to see if consensus is if it will go linear and/or fast.
 
I am leaning towards the ECMWF and away from the GFS at the moment because the ECMWF more reasonably handles the shortwave ejecting into the Southern Plains later on Thursday, and actually develops a low, while the GFS just maintains the low to the north.

Looks like a possible round of severe weather in the Plains Thursday with a very active Friday attm to me. That being said...with the low developing late Thursday over the SP...could see the surface wind field back a little bit and give some decent evening chasing conditions.

Models far from consensus right now but expecting Friday to be the more active day attm.
 
OK looks like I will be wrong, but Thursday's risk area will need to be expanded to cover much of the midwest. SPC's 4-8 day outlook seems to be getting a relatively good handle on the situation. Tornado threat will follow real close to the low track I imagine, which is still somewhat in doubt given model uncertainty. At least they're converging on timing.

EDIT: Jeeez. Just wanted to point out that an analog of last night's GFS for Thursday that's coming up is May 8 1988 which was a record outbreak across the Upper Midwest and I believe it set the all time record for tornadoes in a day for Iowa. Still breaking down the analogs...will let you know if I find anything else interesting.
 
OK looks like I will be wrong, but Thursday's risk area will need to be expanded to cover much of the midwest. SPC's 4-8 day outlook seems to be getting a relatively good handle on the situation. Tornado threat will follow real close to the low track I imagine, which is still somewhat in doubt given model uncertainty. At least they're converging on timing.

EDIT: Jeeez. Just wanted to point out that an analog of last night's GFS for Thursday that's coming up is May 8 1988 which was a record outbreak across the Upper Midwest and I believe it set the all time record for tornadoes in a day for Iowa. Still breaking down the analogs...will let you know if I find anything else interesting.
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FWIW, I checked Severe Plot, it has 57 tornadoes recorded that day.

The 65-70°F air with the sfc Td of up to 60°F looks to punch all the way up to a line form Chicago to Sioux Falls Thursday-Friday. Right now, the LIs painted by the GFS are down to -6.40 around the Sioux Falls to Topeka line Thursday evening. Right now, it appears to me that most of the convection should go linear due to most unidirectional shear (GFS) As Alex pointed out, there may be a couple supercells near the sfc low, but currently, I doubt that there will be many of those.
 
AFTER OBSERVING MODEL RUNS FOR THE PAST FEW DAYS..THIS IS A
SYNOPTICALLY EVIDENT SEVERE WX EVENT...WHICH IS SEEN ABOUT 5 TIMES A
YEAR ACROSS THE COUNTRY.

-DVN-

I concur. This is looking like there will be an outbreak of svr wx somewhere in the Central US.
 
After looking at the latest GFS, I'm liking Kansas more and more. I was looking at going out Thursday, possibly into OKC, which I may still do. As mentioned before, models are already showing good LI values across a wide swath of the middle of the U.S. Timing of this system I believe is still up in the air, but it does appear more evident that Thursday is the day.
 
I think there are two main possible target areas at play: first is northeast of the surface low across northcentral Kansas into southeastern Nebraska, and the second area appears to be from Central Oklahoma into Eastern/Northeastern Oklahoma. Eastern and Southeastern Kansas looks horrible at this time, but if the shortwave digs a little further south or north both of these possible targets will change significantly.

I personally like Northcentral KS/SE NE; being northeast of the surface low with incredible positive vorticity advection, steep lapse rates, great localized low-level shear and slower moving storms.

Sometimes I will go for the second area, which looks to be Central Oklahoma; great shear, faster moving storms, larger area of instability (most of the time)

Either target looks good right now; historically in setups like this I've caught tornadoes in both areas, so it will be a tough decision come early Thursday morning......I'm just glad there is a good looking setup.
 
From my experience with this type of system I'd want to go where the upper level winds have a westerly component which is OK/TX. The wind field is advertised to be highly unidirectional north of there less the warm front boundary somwhere in NE where you at least get some backed surface flow. The NAM and GFS plant a solid dryline at 18z in OK/TX with robust upper flow and some turning with height. Main caviat I see is the potential for some morning convection which will need to clear out for some solar to destabilize the atmosphere.
 
I tend to agree with Simon on the idea of the two best areas based on the best dynamics. The shear will be incredible, no doubt, throughout East Oklahoma/Kansas/Nebraska. The key will be the best dynamics, and the main vort max and associated surface low is best area #1. There the low level shear will be maxamized east of the low and that's where the best tornado threat exists in my opinion. The other area will be wherever the upper jet streak is located (~250mb). The 27th 12z NAM has it moving through North Central/Northeast Oklahoma/SouthCentral Southeast Kansas, making that area best area #2. Either way there will be tornadic supercells all along the dryline, it's just the most long lived supercells will exist in those two areas. Unfortunately I'll be missing out on this event.
 
Judging from this morning's Eta and GFS, I'd have to say that E. KS will be dealing with an MCS due to an unfavorable shear vector orientation for isolated storms. Limited moisture at the surface spells trouble for any storms trying to become tornadic (high LCLs). However, further north (NE/IA) could have a much better opportunity for discrete cells, and in the high shear/low LCL environment, a better potential for tornadoes.

In my opinion, I'm glad the models have some more time to make up their minds, because right now, it doesn't look great (save for extreme wind fields).

Gabe
 
It certainly does appear as though moisture could very well be the limiting factor, which is relatively common for these early-season systems. Looking at the new 12z NAM output, the dryline appears to be nearly N-S along I35 and I135, which makes for a nearly 30-45degree angle between it and the deep-layer shear vector (Note: link will change when 12z data is replaced this evening). Now, this certainly isn't ideal, but it's much better than being parallel! With intense wind fields throughout the target area, keeping up with these thigns may be quite a challenge. Otherwise, if we assume some insolation to bump temps into the 70s, the dewpoint depressions will likely be in the 15-20F range owing to relatively dry upper-50 Tds. I'm also a little concerned about the fact that the all the models significantly overforecast moisture return with the last system we had (3-12), with the afternoon obs being 10 degrees lower than model forecast in many places. Current Surface Obs from the southern plains and the Gulf of Mex indicate that the true moisture is nowhere to be seen right now (or even much in the way of good modified cp air, with only 50-55F Tds in the northern Gulf), and the circulation pattern in the Gulf indicates that we won't see it.

Now, given the intensity and orientation of the vort max slamming through KS, I do think we may intense, linear upward motion that may try to force a squall line up there. I haven't looked too much farther north, since I'm not planning on chasing that way. However, as someone else has mentioned (Justin, IIRC), mid-upper level flow will be significantly backed in that area, which also tells me squall, or, maybe, supercells that cross the warm front quickly and become elevated.

My very, very prelim target? With more veered mid-upper level flow, slightly higher Tds, and a little more removed from intense forcing associated with DPVA from the vort max, I'm aiminig to stay in OK. I also hoping for something on Weds, as that looks pretty tasty if we can get initiation (but I'll save that for the other thread).
 
Jeff, you gave in! lol :p

Yeah, I didn't actually look at the shear vector map when I made my previous comment...I inferred a bad orientation based on the backed flow at 500 mb and the southerly LLJ. While this unfavorable orientation will be problematic in E KS/NE/IA, it looks as though most of OK east of the dryline will have an excellent shot at discrete storms.

As far as moisture is concerned, the T-Td won't actually be too bad. Eta indicates low 70s Ts with low 60s Tds. Assuming a well-mixed boundary layer yields an LCL height of 500-600 m. Not too shabby...

Gabe
 
I think there is enough low-level turning to make THUR a good cold-core day wherever the surface low finally settles (as of now, either southeast NE or northeast KS) with plenty of low-level moisture (helping to support a solid 500-750J/kg SBCAPE) and cold H5 flow (further steepening lapse rates) and very strong PVA. I do, indeed, hate to see that southerly 500mb flow -- but the low-level turning somewhat compensates for this (given the supercells will be shallow), and pretty much falls into a 'cold core' setting. I'll likely be leaving Detroit tomorrow, and play WED, and then head northeast for THUR (to the surface low).
 
I think mid-upper wind orientation is still somewhat favorable in southern Kansas for semi discrete activity and since I cant travel too far south into oklahoma and cold core setups (athough very tornado productive) arent somthing I feel like chasing right now, I think I will target Kan-Ok boarder region for now. If surface low ends up placing itself a little further south I may go Cold core though. Obviously we could use a little better moisture but low sixties have crept further north into central texas with latest surface obs and once that southerly wind kicks in as lee trough develops moisture will advect northward quickly so NAM moisture forecast may easily verify.
 
Definitely looks fairly decent according to the GFS in BUFKIT for areas of SW Iowa and NW Missouri. I'm afraid that the low wont make it quite that far east on thursday though. The main limiting factors i see in the forecasted soundings right now is the over abundances of mid level moisture, keep the air from cooling fast enough to along for large amounts of instability. Definitely looks like there is potential along the dry line, but keep in mind that there are several instances of there being no tornadoes on the dryline and several near the surface low / boundary interactions when dealing with cold core systems. I think this one is going to be tough to forecast so far out, but definitely worth watching as it has potential for sure.
 
I like the central to northern Oklahoma target as of now. Relatively speaking, the only thing the surface low target has going for it is more backed surface winds. Central to northern Oklahoma should have stronger instability and better deep layer and low level shear. My primary concerns are moisture and cloud cover. If we can get good insolation along the dryline(in OK.) and realize something close to the 60 dewpoints the NAM is calling for, then I think tornadic supercells are a reasonable possibilty.
 
12z to 0z forecast only: Looks to me like a definite tornado day at this point. I'd say probably moderate risk, potential high especially if more higher quality air can get up further north closer to the sfc and mid level low. I prefer the dryline - probably eastern KS, or north eastern OK, but with strong 850 jet in place MO will definitely be under the gun toward the end of the day and throughout night with potential strong tornadoes and long track supercells. Potentially tornadic areas: eastern OK, ne AR, all MO, eastern KS, parts of eastern NE, southern IA.

I do note in some ways this is similar to last weeks big system, but coming in a bit more north, and right now a bit further west. As I recall the last system had better dewpoints too (anyone remember?) I'm thinking it was 60's whereas many northern areas here are showing 50's. The dynamics do look similarly very strong though.

Either way even if then northern area with big dynamics (edit: and lower dewpoints) bust a bit, I don't see how the southern area along the dryline such as ne OK could. The last run of the NAM shows the sfc low positioned a bit further east than previous influencing MO quicker. We'll see how the dance of the models goes in the hours ahead.

EDIT: Thinking about this I may have given a bit too much credit to the northern areas showing 50's dewpoints. I think they will still have some torn potential, but this will be diminished some because of lack of moisture. I'm still thinking at least a moderate risk though. For my area (based this far out and subject to change), I'd probably be tempted to go down into the juicier air with 60's dews rather than right on top of the sfc low and mid-upper level forcing direct pathway; however this might still end up being eastern KS, and ne OK. SPC now mentions change for early forcing to cause convection early with possible stabilization and outflow boundary conditions. It will be interesting to see how this plays out. I'll have to look a bit further into Jeff's idea of northern Tx - that of course would be more preferred for me since closer to home. I haven't yet checked today 12 run, but may comment further in a bit.

EDIT2: Also I mention MO and chance for long track supercells and torns....hmm with lower dewpoints this maybe a bit questionable, but perhaps still possible. Areas further south may find it possible also. I'll have to look closer as this thing approaches; however MO and night torns - seems to go together.

EDIT3: Wow looking at forecast ehi for thur is surprising - it is all along the red Tx/Ok (se OK and ne TX). With so little further north this may impact my forecast and drag me further south.
 
Well assuming we can clear out the precipitation the synoptic setup is actually quite similar to the November 12th outbreak of last year. I plan on playing near the triple point, and if that looks to bust fall a little further south onto the dry line, however I do think that the big show for "surprise" tors will fall just east of the Surface low. Looking at 21z output from the 00z NAM shows a far more than ample 1500j of sbcape! Of course this all depends on clearing out of morning convection. For fun though, just compare the synopic setup advertised by ETA with this SPC storm data from November 12th....

http://www.spc.noaa.gov/exper/archive/even...1112/index.html
 
As a relatively quick note, I'm actually liking the area in northern TX better on Thursday than areas to the north. The 0z NAM has sped up the progress of the vort max on Thursday, such that I could see relatively widespread convection initiating by early afternoon as the intense vort max slams into the warm sector. Farther to the south, the southern end of the strongest forcing aloft should skirt northern TX and southern OK. The 0z NAM indicates ~65-67F tds down there (I'm highly suspicious of that, but it's a signal nonetheless), which will help boost CAPE a bit. Low-level and deep-layer shear shouldn't be a problem anywhere given the strong, veering winds in the vertical, but the slightly weaker mid-level flow in northern TX will favor slower, more manageable storm motions (Bunker's motion of 40-45kts in that area), while still maintaining 50-55kts deeplayer shear. Depending upon how insolation goes up north, I'm concerned with both the intensity of the forcing aloft and the relatively marginal instability.

The recent dprog/dt from the NAM is a little interesting, since there's a general bias for models to bring systems out of the southwestern US too quickly, which is the opposite of the recent NAM trend from 12z-0z runs. I'm very interested in seeing what the WRF has to show, since it's done pretty well, IMO, this season.

EDIT: There are some similarities to the overall pattern from 11-12, but this one will be several 100 miles south of 11-12 in terms of the low aloft. In addition, the midlevel flow on 11-12 wasn't closed, while it appears that we'll be dealing with a closed low this time around.

EDIT2: I should say that since I'm basing out of OUN / Central OK, I'm not planning on heading to play the triple point to the north unless is looks a LOT better than areas nearer me, which doesn't appear to be the case right now. So, don't take my discussion to be a big discouragement for areas nearer the sfc low, but I do like the southern target better based on current model output.
 
After taking a closer look at the 00Z ETA I have to jump on board with Jeff. The Red River area looks better than points farther North. I am sure things will change again, but right now Ardmore looks good.
 
One thing that must be mentioned and which those who don't live up here might not realize is that we still have a significant snowpack up here from the 17-28 inch snowstorm that blanketed more or less all of Nebraska and northern Kansas last week. I'm not sure that it will all be melted by Thursday... I somehow doubt it. I reckon that will depress the temps here a bit. Dunno what that will do to the chances of surface based convection, but it sure can't help.
 
Im with Jeff as well. Unless things change and NC OKlahoma NE towards SE Kansas begins to look better I will be looking at an area anywhere from OKC South Towards Gainesville Texas (hopefully even a bit further west of this) on Thursday. We havent had a real good dryline set up in this area yet this season but now is the time to start. I also think moisture return in this area is more likley than points North. This will be a good area to chase also after chasing what could be a bust due to the cap along the Texas Oklahoma border on 3/29. Hopefully not and we will get 2 days of Supercells for Oklahoma and or North Texas.
Im also hopng things can fire early enough for a few good hours of chasing and no more of this storms firing at 5pm or later. Depending on Moisture return and cloud cover I could see a moderate risk along the dryline over a fairly large area Thursday from SE Kansas accross the Eastern Half of Oklahoma and into North Central & NE Texas. Anyways jsut my 2 cents.
 
i also have to say iam in agreement with everyone on this issue looks like the prime
target region will be the i-35 area okc to maybe the denton,tx area on thursday, dryline
setup as we all know though will be key to this, so iam saying at this point i-44 east
with best area rightnow for me being i-35 area... also i do see a mod risk day possible
on thursday, with the chance there of a couple large long lived tornadoes in my opinion
if this pans out right, esp along the red river valley area of sc ok into nc tx...

Edit 1: Just also to add looking at some of the latest models i think this could be even
a bit further east then we were thinking but we will just have to see... which would put
most of the svr wx e of okc to e of adm in ok but iam not so sure of this idea i have
a feeling the dryline will stall and we will have a good setup from sw ok into central ok up
along i-44 to close to interstate 35.. could be wrong but thats way i feel.. think models
are proggin it to the east abit to fast but we shall see =) i still think we have a good shot
of something big but still attm have my doubts, gotta see some more runs before i get to
locked in
 
61 td in Waco at 10:45 with a temp of 64. I think higher dewpoints by Thursday might come into play this time. Gfs is still showing LI values around -4 along the Red River for Thursday, with some 0-3 km srh values in the 250-350 range.
 
One thing that must be mentioned and which those who don't live up here might not realize is that we still have a significant snowpack up here from the 17-28 inch snowstorm that blanketed more or less all of Nebraska and northern Kansas last week. I'm not sure that it will all be melted by Thursday... I somehow doubt it. I reckon that will depress the temps here a bit. Dunno what that will do to the chances of surface based convection, but it sure can't help.
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We had a differential heating boundary here in central Iowa on November 12th and that was likely the cause of the sudden turn from non-tornadic supercells into tornadic supercells with large tornadoes.
Lots of things may come into play here than some may not be looking at. The dynamics near the low have been looking better with passing runs. This is similar to the Nov 12th event when people were saying OK and that area for that day, then it kinda pulled a surprise on everyone.
Its the big scale stuff that gives us the greatest potential for chasable storms, but its the almost unforecastable subtle things that turn that potential into reality.


The days leading up to Nov 12, it was looking like a cold core low scenario, then changed as it got closer. What we have is a strong low pressure area with lots of support and dynamics for intensification, that with minor changes could cause severe weather in a number of places.
 
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