4/10/08 FCST: OK/TX/MO/AR/KS/TN/IL/KY

[Michael O'Keeffe]

Thursday looks like a pretty good chase day if the 12z GFS verifies. It is showing a 999mb low in NW Oklahoma along with a nice dryline in C OK stretching into Texas as well as a warm front near the OK/KS border. The dewpoints are ridiculusly high with widespread 65+F across much if not all of C&E OK and TX. A strong 500mb trough looks to be punching into the region as well as a 30-50knt 850mb southerly jet. Couple that with temps in the 80s and good upper level support I would assume we would see a pretty good chase day! Something to watch closely.

 

[Mike Hollingshead]

Anyone check out today's 12z ECMWF on this one? Yikes.

850mb 12z Thursday Morning.

850mb 12z Friday Morning.

500mb 12z Thursday Morning.

500mb 12z Friday Morning.

Talk about a powerhouse. Hopefully the dews after the Monday into Tuesday system will be left around Oklahoma or so. Hopefully it can slow a hair and keep things out of the hills of MO and AR.

 

[Derek Weston]

Apparently the ECMWF is a bit slower with this than the GFS at this point. Certainly hope the slower take wins out... perhaps get a decent second day of chasing in.

At any rate, Texas has been under the gun with this one in any model run I've seen. Continually strong directional shear and CAPE.

 

[Kevin Crawmer]

I will put my two cents in on this one...

The GFS seems to want to keep the bulk of this system to the south while the ECMWF ejects the low on a similar track to the one on Tuesday. The severe parameters available for the GFS seem to put a big bullseye on AR....which is unfortunate given what happened in Little Rock last week and the terrain there is just awful for chasing. The forecast offices in AR and MO seem to advertise more of a heavy rain event, but I am sure this is because of the high QPFs and the recent flooding in both states.

Shear/helicity values are both very high in MO and into IL, but CAPE and LI values struggle to get anywhere near these areas. The GFS did the same thing with Tuesday's system before coming around and feeding some energy up ahead of the low in the last day or so. It seems like the GFS has been speeding up with it of late which isn't good.

 

[Mike Hollingshead]

It'd be nice to get the GFS and ECMWF to come into a bit better agreement on the handling of this one. The 0z ECMWF just came in on COD and it's still sick for Thursday(and maybe even more-so Friday......ouch). Moisture issues should at least be squared away by Thursday. One potential problem is if the 500mb winds back too much. They get close on the ECMWF but I am not sure they will too much, especially since they get better into Friday.

 

[Adam Lucio]

I just signed on here to say I like the ECMWF solution much better. Shows a more agressive and yes, slower system than the GFS. Plus on a local bias level the storm track would make a chase for me a better possibility

The precip levels on the GFS are almost scary, especially for areas that dont need the rain. Regardless it seems someone is going to have an active day Thursday into Friday, very anxious to see what the later runs bring. Id like to see GFS line up with ECMWF.

 

[Karen Politte]

Anyone coming to chase AR Thursday? I mean......you get the odd flooded road here and there...a few mountains...quite a bit of trees...but apart from that it's great!

Joking aside......I would always remind folks that the eastern and southeastern portions of AR are quite chaseable......as you get towards the Mississippi delta area you find yourself in very flat Plains just like OK and TX - only over a smaller area. The biggest damper right now really would be the flooding......you don't want to be chasing that elusive elephant's trunk and then have your road disappear under a new Bayou that just popped up.

As far as Thursday's FCST - quite impressive to say the least. The real kicker of a longwave trough is progged to finally move out into the Plains and points east of there during the forecast period concerned. HUGE divergence in the flow aloft can be seen which is centered at 500mb right over the eastern half of OK by 12Z Thursday. The ETA has a corresponding rip-snorting 995mb low developing in response to the upper system which barrels across central OK by 0Z. The warm sector is progged to maintain good southeasterly surface winds throughout the whole day - and this coupled with ample moisture for severe weather tells me that Thursday is the big day to watch......although every day this week holds potential good chasing for anybody who's out.

Anyways, living in central AR and not wanting a repeat of last Thursday night......I will be keeping tuned quite fervently.

KP

 

[Kevin Crawmer]

Well I guess I will be the first to chime in on the day 3 moderate. It looks like an explosive situation is setting up for Thursday. The models are starting to get along better now. The GFS has dews approaching 70 degrees to the bootheel of MO, SB & ML CAPE close to 1500, an LI of -5, and SR Helicities 500+ over a broad area. If I did my calculations right the storm motions will be NNE at a screaming 85-90 mph. Obviously that is not right, but the winds are at 85 knots at 500mb from the SW and 70 knots from the SE at 850mb.

Anyways, the 06z NAM is even more aggressive with this taking SB and ML CAPE upwards to 2000+ and SR Helicities in the 600-800+ range. The SPC talks about storm mode being “quasi discrete supercellsâ€￾ (whatever that means), quasi-linear bows, and LEWPS. Combine that with the storm speeds, mountains/hills, and flooding and this does not look like a fun adventure for anyone.

My brother-in-law basically quoted Karen about the terrain in eastern AR. My preliminary target based on chaseability as much as probability would be somewhere along the Little Rock to Jonesboro (please not again) corridor on 67 (Karen…how is that terrain?). If the warm front looks like it may surge further north I may stay up in MO/S IL.

Hopefully things change a little and progress this up into central MO and S IL where the sky opens up a bit more and the roads are better. The day 3 outlook for March 12, 2006 had the bullseye in a very similar place and then by day 1 it was centered over the entire state of MO, so it would not be unheard of for the risk to move several hundred miles one way or the other.

 

[Heidi Farrar]

On the issue of chase terrain, the area east of the Black River (in northeast AR) is flat, mostly treeless farmland with a decent network of county roads, provided they aren't still under water (more on that in a sec.). ... Basically you can count on anywhere east of HWY 67/167 and north of I-40 as being flat or reasonably flat. With that said, there is Crowley's Ridge which runs north/south from north of Paragould to Jonesboro. That's still not as bad as chasing in the Ozarks, though, mostly because it's rather narrow. I would like to point out that flooded roadways is still an issue, especially in Lawrence & Randolph Co. Here's a story that ran last night on KAIT, Jonesboro: http://www.kait8.com/Global/story.asp?S=8131705

Otherwise, 18Z-6Z looks like a scary situation for the state of Arkansas, specifically extreme northeast AR (and into the Missouri bootheel as well), where it would appear that CAPE and shear will come together the most between 0Z-6Z, and with LI less than -4. Lets hope we can avoid the third Federal Disaster in less than 3 months.

 

[Dustin Wilcox]

Given that I have exhausted a decent portion of my chase funds, as well as my "skip class days" the more Southern play is likely out of the question for me, not that I would really want to chase that area anyway. Though I am watching what the NAM depicts as a decent little setup in NCNTRL MO near and just east of a progged 987mb sfc low. The NAM has 60+ DP's advecting all the way to the MO-IA boarder with 1500 j/kg capes and a HIGHLY sheared atmosphere, while quite conditional on many factors yet to be played out (i.e. Convective debris), I see some potential for a tornado or two in N MO.

 

[Ryan Pfannkuch]

Due to work commitments in Nebraska lasting until late Wednesday evening...its looking like my only shot at getting out this week is gonna be Thursday...so thought I might as well start chiming in on this one.

Due to the whole drive time/distance factor...I am becoming more intrigued by the possibility of playing along the WF east of the surface low, which at this time appears to focus on the northern 1/3 of MO.

The 12 NAM/GFS are in pretty darn good agreement depicting a 992-ish sfc low near KC at 0z, with a pretty sharp E-W boundary extending out along or just south of the IA/MO border. Although its far too early to make out of the details regarding complications from overnight/morning convection...it appears a decent mid level dry punch should overspread the region by mid-day...with the NAM depicting a solid 1000-1500 j/kg MLCAPE along I-35 northeast of KC at 0z...which is a notable shift northwest from the 0z run.

Below is the NAM depiction of Siggy TOR parameter valid at 0z, which clearly latches on to the strong LL shear along the WF. Although the 9z SREF data is maintaining a more southern focus across southern MO into AR...I would not be surprised to see the higher SVR probabilities tugged a little farther northwest on the upcoming Day 2 outlooks if the latest model trends persist. Still lots of uncertainties though, especially with regard to the degree of destabilization that far north.

Needless to say, "race-chasing" northern MO is not typically my first choice But it might be my only play to get in on this week's action.

Edit: Hey Dustin, looks like you beat me to it by half an hour while I was looking over data Glad to see someone else took notice of this possible northern target as well.

 

[Kevin Crawmer]

I too echo your thoughts. I have been talking with some friends about the possibility of this. Strictly speaking on an SPC standpoint, the MOD is a safe play there because everything comes together down there, but I can see it being shifted well NW and possibly being upgraded to HIGH in most of MO.

On a forcasting standpoint, I don't see how MO can't be in big trouble with this. Adequate dews, somewhat marginal CAPE that seems to be coming around in recent runs, crazy shear, warm front/triple point followed by cold front, etc. I do worry about the need for clearing though from the precipitation Wednesday night. With the CAPE being in question that far north that could be the only fly in the ointment. Arkansas on the other hand has tons of shear and instability, but doesn't get the benefit from the warm front/triple point. I would guess these storms would just fire off the cold front and give the bows which aren't that chaseable anyways.

 

[beaudodson]

I wonder if we could add KY/TN/IL to this thread?

Paducah is talking about the potential for a significant outbreak, including long track tornadoes. Looking at the 850 wind charts, they are showing three maxes on Thursday afternoon and evening. One of those across southwest Missouri and the other over the Bootheel of Missouri into western Kentucky and southern Illinois.

CAPE values coupled with the dynamics should provice ample fuel for tornadic supercells across the region. The 500 mb map is impressive - for those who have not looked.

One note - the EC is slower (by about 12 hours) with this system. It hangs the front back in Missouri into Friday. Other models are a tad quicker. Something to watch as we move forward. Also, according to the northern Indiana, NWS Office, there has been some errors on the sampling of the trough along the west coast. Perhaps significant errors. They are concerned that the models do not have a handle on the evolution of the trough.

(THE GFS AND ECMWF BOTH DISPLAYED WIND SPEED ERRORS OF OVER 30 KNOTS IN SOME CASES...LEADING ONE TO WONDER IF THE MODELS REALLY DO HAVE A CLUE ON SUBSEQUENT TROUGH EVOLUTION. IMPRESSIVE BACKSIDE MID AND UPPER LEVEL FLOW...ONE WOULD ANTICIPATE TROUGH DIGGING WOULD BE CRUCIAL IN THIS TYPE OF SETUP...SOMETHING THAT LOOKS TO BE WELL UNDERPLAYED IN MODEL PROGS. - NWS Northern Indiana)

I am expecting a larger moderate risk than what SPC is showing. I agree with the other poster that they went with the best bet for now. Later forecasts will likely expand the size of the moderate risk and perhaps add a high risk contour somewhere in Arkansas and Missouri.

 

[Donald Giuliano]

Although I'm more interested in Wednesday from a chasing perspective, Thursday looks like the real show to me. Assuming the model forecasts continue to look as they do now, I would be very surprised if SPC did not issue a high risk on the Day 2, because if this situation doesn't warrant it I don't know what would.

If the NAM/GFS verify, we're talking about a persistent and large area of 50-70 kt 850 mb winds over an unstable, uncapped warm sector throughout the entire day! I can think of only one tornado outbreak case I've examined that exhibited this areal magnitude of extreme low-level shear superimposed over what is likely to be 1000-3000 CAPE. Of course this system has a little ways to go yet before verifying and I can't see any way the situation can get any more ridiculous than this, as there's not really anywhere to go but downhill at this point, so perhaps the next model run or two will back off a bit on the insanity.

As things stand right now, however, April 3-4, 1974 is probably the closest comparison I can come up. Although I haven't had the chance to make a detailed comparison, a quick glance shows interesting similarities between archived maps for 00Z 4 April 1974 and this morning's NAM forecast for Thursday evening.

 

[Adam Lucio]

Your not alone in the warm front chase thoughts. I too was pondering a more northern chase, hoping that it can light up in southern or perhaps central IL as well, tho I agree MO looks better, I dont think IL can be ruled out just yet.

The best moisture seems to be in MO, with the backing of the winds near the center of the low I would put money on a few tornados from northern MO into central IL, especially if the warm front can move through earlier in the day which has much better terrain. I have to make this a one day chase, so heading too far south is not an option to me.

GFS seems to have slowed down and placed the low further west than in previous runs. It also puts the best CAPE into SErn MO it seems. Id like to see it bring it to the east a bit to put the better target into more chaseable terrain. Especially with the insane storm speeds that are likely.

Right now that is the card im "wishcasting" for. Future runs will paint a clearer picture.