4/04/11 FCST: TX, OK, KS, MO, IL, IN

[Matt Hunt]

Monday is looking like a better day than Sunday for a potential severe outbreak. Dewpoints into the upper 60s from TX all the way up to IN. The dryline through central OK and a warm front extending from SE KS to central IN. 12z GFS shows CAPE above 2000 for central OK east of the dryline and up into the Ohio Valley south of the warm front. Very nicely curved hodographs as well. I'm pretty amateur in forecasting, but it looks to me like a good chance for an outbreak along the dryline in OK and TX, and even a chance for some activity along & south of the warm front up into the Ohio Valley. That's what I'm hoping for so I get a chase within a few hours of home! Southern IN isn't great chase country, but it's better than nothing!

 

[Derek Weston]

Monday is looking like a better day than Sunday for a potential severe outbreak. Dewpoints into the upper 60s from TX all the way up to IN. The dryline through central OK and a warm front extending from SE KS to central IN. 12z GFS shows CAPE above 2000 for central OK east of the dryline and up into the Ohio Valley south of the warm front. Very nicely curved hodographs as well. I'm pretty amateur in forecasting, but it looks to me like a good chance for an outbreak along the dryline in OK and TX, and even a chance for some activity along & south of the warm front up into the Ohio Valley. That's what I'm hoping for so I get a chase within a few hours of home! Southern IN isn't great chase country, but it's better than nothing!

Major issue I see is unidirectional shear.

 

[David Reimer]

4/04/11 FCST: TX, OK, KS, MO, IL, IN, KY, TN, AR, LA, MS, AL

While I was skeptical at first, I'm beginning to agree that Monday has the potential to bring huge implications to a large part of the SE United States (not to forget the Great Lakes) based off the 12Z GFS. The one thing I don't like off this morning's 12Z GFS is the rather SSW flow at 500 MB. This makes the wind profile rather unidirectional by Monday evening across AR/LA, however 850's seem to be more backed as you head a little further east. At this point, I'm not going to get down into the details of the LLJ as we're not even within 84 hours yet. While this may reduce the tornado threat slightly, I'm becoming concerned that we could have a widespread, significant severe weather event across a large area. With the widespread warm sector and progged instability values, not to mention the open gulf, this event has the potential to be rather ominous.

I've posted a discussion over at www.TexasStormChasers.com - Click here to read it.

 

[Jim Parsons]

The 700mb temps look pretty high on both the 18z & 00z runs....Poss another capped event or is there something I'm missing that would break this???

 

[James Gustina]

Looks like the warm front is lifted well to the north here on the 18Z (but its the 18Z so we'll see). Surface winds are nice and strong out of the south for most of the day over IL/IN/OH with dews around 65+. Like David said, the gulf opening up like this with strong moisture return is definitely going to make this an event to watch. For the southern half of where this svr outbreak could occur, it looks like the dryline'll be into eastern OK/TX and cutting Missouri in two before the cold front overtakes it in the mid-evening. The shear profiles do look undirectional for most of Indiana, Ohio, and Kentucky but theres a lot more turning the further south you go into the warm sector. Interesting setup and definitely gonna be a big one for chasers I think.

 

[Jim Parsons]

Mon 18z seems to be showing a weakening of the cap around central MO east into IL....It seems to be getting into the area of Skip's magic number of -3, needed to have initiation.

 

[Skip Talbot]

Mon 18z seems to be showing a weakening of the cap around central MO east into IL....It seems to be getting into the area of Skip's magic number of -3, needed to have initiation.

Well, 0 or less means there's no cap at all. A negative cap index actually means the air is unstable (just as a negative lifted index does). The cap is a double edged sword. Its going to burn us on Sunday, preventing initiation on the dryline (maybe), and now on Monday it looks like too little of a cap is probably going to result in a huge linear mess that goes up way too early. Last night's GFS and this morning's NAM indicate the cap burning off by noon. The fast moving cold front is going to result in a ton of forcing. Too much forcing + no cap = too many storms before the environment can destabilize. The cold front starts its push on Sunday night too though. I expect storms to fire Sunday evening across most of the warm sector, and they will be ongoing across eastern IA/IL/MO/AR on Monday morning. This elevated activity may eventually become surface based as low level instability/surface temps increase. However, given the veered surface winds, fast moving, undercutting cold front, and interference from what may be a nearly solid line, I expect mainly a linear mode with perhaps a few embedded supercells. Tornadoes are not out of the question, probably more so in the southern MS valley if stuff can stay more discrete and where the instability is greater, but for the most part this setup is probably going to be a huge crapshot with messy storms everywhere and a few isolated tornado reports.

I'm pretty surprised at how progressive the models have become. I was expecting the models to actually slow down and Monday would become the main event across eastern IA/western IL/MO/AR. Now its looking like the lined-out, sloppy seconds day with Sunday taking precedence, and Monday shifting more and more east with each run into the OH river valley southwest to jungle of LA/MS.

 

[Matt Hunt]

Exactly what I was thinking looking at the latest runs. It just keeps looking less and less promising as we get closer. Plus the little bit of directional shear that was present in earlier runs is now turning even more unidirectional. There might be a chance at some embedded tornadoes, but it looks like primarily a straight-line wind event, if anything.

 

[James Gustina]

Its starting to look really squall-tastic right now. Cold front is swinging through by 19Z with weak directional shear and upper level winds. I'd definitely agree with whats been said so far: sloppy, squall line/MCS with embedded tornadoes.