2/27/11 FCST: KS, OK, TX, MO, IL, AR, LA, MS

[Mark Sefried]

Both the GFS and European models are catching onto what appears to possibly be a strong system for Sunday for parts of the Southern Midwest and the South. The GFS this morning has the low down to 985 mb by 12 noon Sunday over Eastern KS and the European has a 986 mb low over SW KS at 6 PM . Too early to tell if its going to be a decent storm as far as severe weather, however if may be something worth keeping an eye on especially for OK and NW TX if the European model verifies.

 

[Skip Talbot]

This system looks like it could possibly be stronger than Thursday's Day 2 moderate risk. The 500 mb trough digs a lot deeper, is significantly stronger (110 knots on the 12z GFS!), and suface winds are stronger and back better across the warm sector. Significant tornado parameters are already plotting over 5 in the lower MS valley and over 3 all the way up by St. Louis at 6pm. Not bad for February! I'd like to see Thursday's system clear the area before I get too wrapped up in the details for Sunday. One awkward thing about this setup is the displacement of the low level jet from the mid level trough. The best 850's are over the MS river at 0z while the 110 streak is just rounding the base of the midlevel trough over central Texas. Still with 60 knots at the midlevels starting to overtake the MS valley warm sector by 0z, we should have enough lift and shear. This looks like it could be a big nocturnal event too as the extremely strong trough, which arrives overnight, creates a lot of dynamic forcing coupled with warm air advection from the low level jet. Unfortunately, from a chase standpoint this setup might suffer a lot of the same problems as Thursday's including fast storm speeds over unfavorable terrain and at night. The better directional shear may help slow the supercells down as they move against the flow, however, and we may see stronger, more discrete supercells with this setup with what looks like a little better forecast instability and the later arrival of the trough. The GFS is bouncing around with timing on this one, and that will affect the outcome of this event greatly, but this is one to watch very closely.

 

[Mark Sefried]

Agree with skip on Sunday's system being even possibly stronger than Thursday's Moderate risk. The European does not eject the system out into the Southern Plains as quickly as the GFS. So right now its just a matter of what model u want to trust as far as timing/location in concerned. Usually when both the GFS and the European are showing a strong system it verifies. It will be intersting to see what the models show the next several days. Since this appears to be shaping up on a weekend, I imagine there may be a few chasers itching to go chasing assuming it appears to be a nice severe weather producer with future models. Have fun tying to keep up with the storm forward motion though assuming they fire in the daylight hours. (~:

 

[jamesmseitz]

Robert Hurkes and I also think that this one has the possibility of being the one to chase. The winds are backing more on this one but the instability on this system seems to be poor as well and timing as Skip said is a issue. Still when the NAM come online tomorrow and the Thursday's system out of the mix both models will get a better hold on it. Still believe this one is the one to watch...... just wish the storms would slow down a bit

 

[Rob H]

With such a deep low progged (992mb) I'd expect to see some better backed winds closer to the low and better moisture advection, but I'm guessing subsidence from the converging jet over the Upper Plains is causing some issues with surface winds and moisture. There's a 'tongue' of higher Theta-E south of the warm front in S MO, and the LLJ really kicks in (60+ kts) around 00z - hopefully intersecting with some outflow boundaries from the junk going on in that area earlier in the day. At this point I think I'd want to be deep in the warm sector, and then move closer to the warm front as the night went on - but these storms will be cruisin' along and might not allow for that type of strategy.

 

[Brett Roberts]

The difference in timing between the GFS and ECMWF today is quite significant, with the latter being much slower. This is very reminiscent of the model discrepancies for several early-season events last year, if I remember correctly.

If the ECMWF is to be believed, the threat area on Sunday afternoon and evening could extend as far west as the I-35 corridor in OK and N TX, making the chase prospects much more appealing. Unfortunately, the GGEM is firmly in the faster camp, showing the H5 trough axis plowing through OK by 28/00z. Given this, the known bias of the European to hold energy back too long in the Desert SW, and the fact we're in a La Nina year, I'll reluctantly hedge towards the GFS solution for now.

Regardless of timing and location, the quality of moisture available for this system looks to be notably better than tomorrow's, so perhaps a more chaseable setup will unfold in the lower MS River Valley if we get lucky in those two categories.

 

[Mike Smith]

Just looked at the 00Z NAM valid 6am Sunday and I'm pretty impressed. CAPE is forecast to already be ≥1,000j over a good part of KS and OK. Pressures falling rapidly. The 250mb jet is 150kt over far NW Mexico.

While this might not be a good chasing situation because of fast storm movements, it could -- potentially -- be a potent tornado producer with the very fast movement making effective warnings a challenge.

 

[Trey Alvey]

This system certainly looks stronger and more widespread than tomorrow's. Moisture will be more plentiful for a couple reasons. Tomorrow's system will act as a primer and help bring better moisture content/quality further north from the GOM and Carib. This will be more easily accessible for Sunday/Monday's episode, since the front will stall along the Gulf Coast and doesn't have a strong high pressure behind it.

Another interesting feature is the extensive EML/dry punch across much of the warm sector unlike tomorrow's severe event.

Also, models have trended faster and I'd lean towards a faster solution as opposed to the slower solutions shown earlier in the week. We're in a progressive La Nina pattern and nothing is blocking the system downstream. I believe someone already mentioned it, but the EURO does tend to have a slow bias with systems ejecting out of the SW.

Finally, this system will have better directional shear particularly in the lower levels.

 

[Mark Sefried]

I am starting to side wth the GFS more with that low ejecting into the southern plains quicker than the European. Looks like a nice little system to test your equipment for the year for people from near I-35 Eastward across far Southern KS, OK, and into N. TX. Still concerned about stuff firing during the daylight hours but there is still plenty of time to watch this. Hopefully things set up a little further WEST so you OK chasers can stay out of the jungle.

 

[Kevin Crawmer]

This day certainly has caught my eye given the proximity for me and the setup that has been taking place. There certainly seems to be enough to 'get it done', but I do have some concerns with temp/dewpoint spreads and weather the warm air and moisture will in fact make it as far north as forecast. I have seen some comparisons to 3/12/06 being thrown out there. I remember that day that there was more warm air in place. As a matter of fact, there were isolated strong storms the day before the event that led to a lot of large hail and I believe a few tornadoes. There are rain/snow chances in the northern target area on Saturday where the warm front is expected to lie on Sunday. There was widespread CAPE in excess of 2000 in the warm sector and this is not the case for Sunday (as of right now). It definitely has my eye and I have my fingers crossed for an early season chase. Here are a couple links from 3/12/06 for nostalgia purposes and maybe for historical comparisons as far as how similar the days may or may not end up being:


http://www.stormtrack.org/forum/sho...ST-Southern-Great-Lakes-to-Western-Gulf-Coast
http://www.stormtrack.org/forum/showthread.php?8145-3-12-06-NOW-KS-MO

Edit--my eyes are in MO/E KS....not further SW into OK.

 

[Trey Thee]

This day certainly has caught my eye given the proximity for me and the setup that has been taking place. There certainly seems to be enough to 'get it done', but I do have some concerns with temp/dewpoint spreads and weather the warm air and moisture will in fact make it as far north as forecast. I have seen some comparisons to 3/12/06 being thrown out there. I remember that day that there was more warm air in place. As a matter of fact, there were isolated strong storms the day before the event that led to a lot of large hail and I believe a few tornadoes. There are rain/snow chances in the northern target area on Saturday where the warm front is expected to lie on Sunday. There was widespread CAPE in excess of 2000 in the warm sector and this is not the case for Sunday (as of right now). It definitely has my eye and I have my fingers crossed for an early season chase. Here are a couple links from 3/12/06 for nostalgia purposes and maybe for historical comparisons as far as how similar the days may or may not end up being:


http://www.stormtrack.org/forum/sho...ST-Southern-Great-Lakes-to-Western-Gulf-Coast
http://www.stormtrack.org/forum/showthread.php?8145-3-12-06-NOW-KS-MO

Edit--my eyes are in MO/E KS....not further SW into OK.

Kevin, that is a good point. Based on my past experiences, I am also concerned about moisture return for this system. I can remember instances where models showed a substantial system moving through, then moisture return did not materialize and resulted in a few isolated storms and some hail. At this point I'm not counting on strong moisture return even for my area (Tulsa metro). I do think south of the OK/KS line we will have some significant storms, at least that is the way it appears at this point, but how widespread and what the tornado threat will be is too hard to nail down at this point. Sometimes these early systems don't get nailed down until the last minute.

 

[Kevin Crawmer]

A couple things that stood out to me about 3-12-06 were the morning cells that fired along the warm front in KS and MO and produced tornadoes and also that monster cyclic supercell that I believe started in KS and died in OH.

As far as Sunday goes, the northern target may have up to 6" of snow tonight and temps are forecast to stay low until Sunday in these areas. I would believe massive amounts of dense dfog would be present given the snow melt and small temp/dew spreads. The more photogenic storms may lie in OK where the best parameters appear to be juxtaposed anyways at the moment.

 

[Donovan Gruner]

I'm still not very convinced about this setup. Models aren't in agreement regarding instability at all. The only target I really see at this point would be near the low. We'll see how it pans out in the next few days, but my hopes aren't up quite yet.

 

[Jeff House]

Agree with the moisture bears here. Front is clearing the Gulf Coast, which is really bad news for an event in just 48 hours. We would want the front to stall in Texas, which would lead to quick and excellent moisture return. Not the case today. I believe even Deep South Texas will dry out later today.

Also agree the northern target is out due to snowcover. I would target the DL bulge in Oklahoma. Current progs show a just right Goldilocks cap there. 850 winds might be a little veered, so it would have to be watched as the day approaches. Things can change, esp with a strong low. Another problem, regardless of the above, is strong surface winds that would tend to mix out sfc moisture.

Closing on a positive note, it should be a dynamic system capable of producing if the thermodynamic set-up is favorable.

 

[Skip Talbot]

We might be entering a race here to break the cap before the sun goes down. The last three runs of the NAM have been showing a stout cap that starts to erode at 0z. That wouldn't be a problem in late spring when we've got more daylight to work with, but in this case the sun is going down ust after 6pm (0z) in OK/KS so you're looking at night chase if this is the case. NAM actually holds off initiation until somewhere between 9pm and midnight and over western AR. With the inhibition erosion starting hours before then, a ridiculously strong trough, and sharp frontal boundaries, I'd expect initiation a little sooner than that given the lift and forcing. GFS isn't much better with the cap. The cap index isn't too bad between 21z and 0z with values getting down to about 1 on the 12z NAM. That's more than breachable given the lift we should have. Lingering CINH may cause initial updrafts to struggle, however. Moisture looks decent if the return amounts being forecast actually verify. Instability is pretty modest and along a fairly narrow axis, but that's to be expected this time of year. Otherwise a very impressive setup with great looking hodographs, speed and directional shear, and a high risk type trough with 110 knots being plotted at the midlevels! If we had the thermodynamics on this setup locked into place I'd go out on a limb and say this has a good chance of seeing a high risk. But alas, capping issues, questions about timing of initiation, and available instability put this setup into question. For the best chance at a decent chase I'd probably stay near the triple point in south central KS for late afternoon/early evening initiation of potentially tornadic supercells. If the cap doesn't break though, you're looking at following that triple point east towards MO/AR and setting up for another nocturnal outbreak in the jungles (not fun).

Cap index, showing breakable values along dryline/warmfront:
http://68.226.77.253/models/eta/central/CENTRAL_ETA212_ATMOS_LSI_57HR.gif
http://68.226.77.253/models/eta/central/CENTRAL_ETA212_ATMOS_LSI_60HR.gif

Inhibition lingers on through 0z:
http://www.twisterdata.com/data/mod.../25/12/NAM_221_2011022512_F57_CIN_SURFACE.png
http://www.twisterdata.com/data/mod.../25/12/NAM_221_2011022512_F60_CIN_SURFACE.png

NAM holding off initiation until afte 9pm:
http://www.twisterdata.com/data/mod...25/12/NAM_221_2011022512_F63_CREF_SURFACE.png
http://www.twisterdata.com/data/mod...25/12/NAM_221_2011022512_F66_CREF_SURFACE.png