Severe Potential March 2nd/3rd: OV, TN Valley, Mid-South, Deep South, Mid-Atlantic, Carolinas

[audioguy3107]

You would work at SPC before you make a statement like this, if you were a reasonable Met. Describe how the are WAY too conservative, knowing everything they know about their jobs. Thanks in advance.

Following the SE mets for close to 5 yrs now, I can assure you Cheez is a reasonable met. Based on what the models have been suggesting the last few days, would you have a threat area outlined in the longer term? If so why, and if not, why not?

[QVectorman]

Do you guys have any idea who ohleary is? If he is who I think he is you should have tremendous respect for him. And I absolutely back him on this. The models have not shown ANYTHING resulting in a 100 % tornado outbreak. Every run of everything has had the dynamics separated from the thermo dynamics. Not once have they matched up so why would the S P C commit this far out to an outbreak when clearly the models have yet to combine the ingredients? Not once have the models positioned CAPE lift and quality shear over the same location. Ingredients are there. Just not matching up

[Stebo]

Do you guys have any idea who ohleary is? If he is who I think he is you should have tremendous respect for him. And I absolutely back him on this. The models have not shown ANYTHING resulting in a 100 % tornado outbreak. Every run of everything has had the dynamics separated from the thermo dynamics. Not once have they matched up so why would the S P C commit this far out to an outbreak when clearly the models have yet to combine the ingredients?

A day 4-8 is for 30% risk of severe weather of any mode, not just tornadoes...

[Chicago Storm]

Do you guys have any idea who ohleary is? If he is who I think he is you should have tremendous respect for him. And I absolutely back him on this. The models have not shown ANYTHING resulting in a 100 % tornado outbreak. Every run of everything has had the dynamics separated from the thermo dynamics. Not once have they matched up so why would the S P C commit this far out to an outbreak when clearly the models have yet to combine the ingredients? Not once have the models positioned CAPE lift and quality shear over the same location. Ingredients are there. Just not matching up

lol

[Hoosier]

Do you guys have any idea who ohleary is? If he is who I think he is you should have tremendous respect for him. And I absolutely back him on this. The models have not shown ANYTHING resulting in a 100 % tornado outbreak. Every run of everything has had the dynamics separated from the thermo dynamics. Not once have they matched up so why would the S P C commit this far out to an outbreak when clearly the models have yet to combine the ingredients?

I believe SPC day 4-8 outlook is issued for 30% or greater severe probability.  I don't think it necessarily means 30% or greater probability of a tornado outbreak but someone can correct me if I am wrong. This lack of a risk area talk is a bit of a distraction anyway.  Based on the available 00z runs, I'd be shocked if there isn't one tonight.

[SmokeEater]

Do you guys have any idea who ohleary is? If he is who I think he is you should have tremendous respect for him. And I absolutely back him on this. The models have not shown ANYTHING resulting in a 100 % tornado outbreak. Every run of everything has had the dynamics separated from the thermo dynamics. Not once have they matched up so why would the S P C commit this far out to an outbreak when clearly the models have yet to combine the ingredients? Not once have the models positioned CAPE lift and quality shear over the same location. Ingredients are there. Just not matching up

The problem is, ohleary came in the thread not in good faith. He came in just to start with people, like he does in a lot of threads on this board. He discussed nothing about the upcoming event whatsoever.

[andyhb]

You would work at SPC before you make a statement like this, if you were a reasonable Met. Describe how the are WAY too conservative, knowing everything they know about their jobs. Thanks in advance.

They mentioned that an AOA 30% probability is possible in the last day 4-8.

[audioguy3107]

Do you guys have any idea who ohleary is? If he is who I think he is you should have tremendous respect for him.

You've piqued my curiosity......let the cat out of the bag.....who is it?

Not once have they matched up so why would the S P C commit this far out to an outbreak

I haven't read anyone on here thinking that SPC should be calling for a major outbreak.

[beneficii]

I believe SPC day 4-8 outlook is issued for 30% or greater severe probability. I don't think it necessarily means 30% or greater probability of a tornado outbreak but someone can correct me if I am wrong. This lack of a risk area talk is a bit of a distraction anyway. Based on the available 00z runs, I'd be shocked if there isn't one tonight.

Based on what I've seen tonight, on the next SWODY3 I'd probably put a slight risk approximately from Little Rock to Cape Girardeau to Lexington to Atlanta and back to Little Rock. What do you guys think?

[Hoosier]

Based on what I've seen tonight, on the next SWODY3 I'd probably put a slight risk approximately from Little Rock to Cape Girardeau to Lexington to Atlanta and back to Little Rock.  What do you guys think?

I'd extend it farther north/east into parts of IN/OH and maybe go with a 30% prob south of I-70.

[PatrickSumner]

I'd extend it farther north/east into parts of IN/OH and maybe go with a 30% prob south of I-70.

Hoosier...I will be heading back to Seymour around noon...should arrive in Seymour around 2:30 or 3. What is the main time for these storms? Will I be impacted on the way???

[TheWeatherPimp]

DAY 3 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0223 AM CST WED FEB 29 2012

VALID 021200Z - 031200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS OH VALLEY STATES TO

CENTRAL/SRN APPALACHIANS AND LOWER MS RIVER REGION...

..SYNOPSIS

WRN-CONUS SYNOPTIC-SCALE TROUGHING DESCRIBED IN DAY-2 OUTLOOK IS

FCST TO PROGRESS EWD ACROSS CENTRAL CONUS DAY-3. BY 3/00Z...TROUGH

SHOULD EXHIBIT STG POSITIVE TILT...EXTENDING FROM MID-UPPER LOW OVER

MN/ONT BORDER REGION SWWD ACROSS CENTRAL PLAINS TO BASAL SHORTWAVE

TROUGH OVER NRN NM. NEAR END OF PERIOD...CONSENSUS OF

OPERATIONAL/SREF GUIDANCE REASONABLY POSITIONS TROUGHING ALOFT FROM

N OF LH SWWD ACROSS PORTIONS IA/MO/OK TO SRN NM/FAR W TX REGION.

AT SFC...2/12Z CYCLONE SHOULD BE POSITIONED INVOF SWRN MO...AS

FRONTAL WAVE PERTURBED BY WEAK/LEADING MIDLEVEL SHORTWAVE. SFC LOW

IS EXPECTED TO MOVE NEWD AND DEEPEN THROUGHOUT DAYLIGHT

HOURS...REACHING NWRN INDIANA/WRN LOWER MI AREA BY 3/00Z. AT THAT

TIME...COLD FRONT SHOULD EXTEND SWWD ACROSS INDIANA...AR...AND

CENTRAL TX...WITH WARM FRONT SEWD INTO CENTRAL APPALACHIANS. THIS

WARM FRONT WILL BE SEPARATE FROM DAY-2 VERSION OVER SRN PLAINS/LOWER

MS VALLEY REGION...THAT WILL HAVE DISSIPATED BY EARLY DAY-3. BY

3/12Z...COLD FRONT SHOULD REACH WRN NY...CENTRAL/SRN

APALACHIANS...CENTRAL/SRN MS AND UPPER TX COAST.

..MS/GA/AL TO OH VALLEY STATES

GROUPS OF TSTMS MAY CARRY OVER FROM DAY-2 PERIOD OVER PORTIONS

MID-MS VALLEY TO MID-SOUTH REGIONS...MOVING NEWD TOWARD OH VALLEY

STATES. WHILE THIS ACTIVITY MAY BE ELEVATED INITIALLY...COMBINATION

OF DIABATIC HEATING AND STG BOUNDARY-LAYER THETAE ADVECTION SHOULD

DESTABILIZE FOREGOING AIR MASS ENOUGH TO YIELD SFC-BASED EFFECTIVE

INFLOW PARCELS. STG DEEP-LAYER SPEED SHEAR AND MID-UPPER WIND

SPEEDS INDICATE FAST STORM MOTIONS ARE LIKELY...POTENTIALLY AOA 50

KT...WITH DAMAGING GUSTS COMPRISING BULK OF SVR EVENTS...AND

TORNADOES ALSO POSSIBLE.

ANOTHER AREA OF TSTMS WITH WIND DAMAGE/TORNADO POTENTIAL SHOULD

DEVELOP ALONG/AHEAD OF SFC COLD FRONT FROM LATE AFTERNOON INTO

OVERNIGHT HOURS...OVER PORTIONS KY/TN/MS...IN FAVORABLE

BOUNDARY-LAYER MOISTURE. THIS ACTIVITY EVENTUALLY SHOULD EVOLVE TO

QUASI-LINEAR GIVEN NEARLY PARALLEL NATURE OF MEAN FLOW WITH RESPECT

TO ZONE OF LOW-LEVEL ASCENT. HOWEVER...VERY STG LOW-LEVEL AND

DEEP-LAYER SHEAR...ESPECIALLY DURING EVENING OVER PORTIONS KY/TN AND

NRN MS/NWRN AL...INDICATE FIRST FEW HOURS OF CONVECTIVE REGIME MAY

INVOLVE FAST-MOVING/SFC-BASED SUPERCELLS AND ACCORDINGLY ENHANCED

TORNADO POTENTIAL. EXTENT TO WHICH THIS REGIME WILL LINK WITH

EARLIER/OH VALLEY CONVECTION IS UNCERTAIN...AS ARE IMPORTANT MODE

CONSIDERATIONS SUCH AS PACE OF LINEAR EVOLUTION. UNCERTAINTY

REGARDING HOW FAR SW BACKBUILDING WILL OCCUR...INTO PROGRESSIVELY

STRONGER CAPPING AND WEAKER LOW-LEVEL CONVERGENCE...IS MANIFEST AS

DECREASING UNCONDITIONAL PROBABILITIES OVER LA AND E TX.

..EDWARDS.. 02/29/2012

[Cheeznado]

The 06Z NAM has some incredible forecast soundings in the OH valley Friday afternoon. This would be a very nasty outbreak,probably some violent tornadoes.

[Stebo]

The 06Z NAM has some incredible forecast soundings in the OH valley Friday afternoon. This would be a very nasty outbreak,probably some violent tornadoes.

Yes IN/OH/KY all really would be under the gun if the NAM is right.

[QVectorman]

The 06Z NAM has some incredible forecast soundings in the OH valley Friday afternoon. This would be a very nasty outbreak,probably some violent tornadoes.

Yes IN/OH/KY all really would be under the gun if the NAM is right.

Yup have to agree...the 0z GFS really brings everything together and has good moisture...it would be a nasty storms with an isolated tornado possible over west Tennessee into northern Miss. if that solution were to verify. Still not the best lift over those areas but the thermodynamics and dynamics would compensate some what. The NAM has crazy/wicked profiles along southern IL and southern IN for 18z and then for SW OH at 0z but the moisture and lift isn't as abundant on the 0z NAM relative to the GFS. I will say on the 0z NAM if the lift and moisture improved and kept everything else the same it would be a good day to chase across southern IN and SW OH

[Stebo]

This is an upward trend... Also I would argue SPC's outlook might need to be shifted a bit West, which I expect with time it will be.

[andyhb]

Yup have to agree...the 0z GFS really brings everything together and has good moisture...it would be a nasty storms with an isolated tornado possible over west Tennessee into northern Miss. if that solution were to verify. Still not the best lift over those areas but the thermodynamics and dynamics would compensate some what. The NAM has crazy/wicked profiles along southern IL and southern IN for 18z and then for SW OH at 0z but the moisture and lift isn't as abundant on the 0z NAM relative to the GFS.

I saw your edit

[QVectorman]

I saw your edit

Ya I'm not seeing good vv's over Tenn or Miss on the GFS like I would like to see for tornadoes and strong storms but with that forecasted environment on the GFS the dynamics and thermodynamics should be enough to generate a rouge tornado or two so I had to factor that in

[Fred Gossage]

Ya I'm not seeing good vv's over Tenn or Miss on the GFS like I would like to see for tornadoes and strong storms but with that forecasted environment on the GFS the dynamics and thermodynamics should be enough to generate a rouge tornado or two so I had to factor that in

The fact that you're not seeing stronger vertical velocities probably means that things are much more likely to stay discrete, instead of lining out. Most supercell tornado events from the MS Valley eastward are associated with a weakly capped environment and very subtle forcing. If those stronger vertical velocities were present, there would likely be either not enough storm spacing and/or a quick transition to linear mode.

-------------- Onto the discussion I came here to post ---------------

Here's my big concern for down this way....

Yes, the main surface low goes north, but.... by late in the afternoon, a powerful 140-150 kt upper-level jet streak is approaching the Deep South and Tennessee Valley from Arkansas and Louisiana, and this spawns a secondary 50-60 kt 850-mb jet max over Mississippi late in the day that shifts eastward across Alabama during the overnight. All of the models are trending closer and closer toward closing off a secondary surface low somewhere between Little Rock, AR and Clarksville, TN in response to this second upper-level disturbance. However, even without them actually showing a closed off surface low yet, pressure falls extend down the cold front and surface winds are almost due south beneath the southwesterly (but with trajectories still off the Gulf of Mexico, unlike last week) low-level jet that very rapidly intensifies after dark. So, while the main surface low goes northward into the Great Lakes... another very potent disturbance approaches our area by late afternoon and evening, and we have shear profiles rapidly ramp up toward dark, with deep-layer shear vectors of 60+ kts and almost due west to east... strongly favoring discrete supercells.

For those of you worried about that main surface low ejecting to the northeast... on November 10, 2002, the main surface low was in southern Canada that morning... with south-southwest surface winds over the warm sector down here... but we had pressure falls down the cold front and a second jet streak come out of AR/LA into TN... and we had major tornadoes down here in MS/AL (with SSW sfc winds and only a 40 kt 850mb jet... and 1 km SRH values around what the NAM is progging them to be, and we know how the NAM almost always underplays the low-level shear this far out). Also, the Candlestick Park F5 tornado in MS in March 1966.... the surface low with that event... was in central South Dakota. If we get a secondary surface low or even pressure falls down the cold front, it's not going to matter where the first surface low is... with that new upper-level disturbance and second low-level jet max coming through.

I have a feeling that some people may be significantly caught off-guard by the Mississippi-Alabama-Georgia portion of this threat for late Friday afternoon through early Saturday morning.....

[wxsmwhrms]

The fact that you're not seeing stronger vertical velocities probably means that things are much more likely to stay discrete, instead of lining out. Most supercell tornado events from the MS Valley eastward are associated with a weakly capped environment and very subtle forcing. If those stronger vertical velocities were present, there would likely be either not enough storm spacing and/or a quick transition to linear mode.

-------------- Onto the discussion I came here to post ---------------

Here's my big concern for down this way....

Yes, the main surface low goes north, but.... by late in the afternoon, a powerful 140-150 kt upper-level jet streak is approaching the Deep South and Tennessee Valley from Arkansas and Louisiana, and this spawns a secondary 50-60 kt 850-mb jet max over Mississippi late in the day that shifts eastward across Alabama during the overnight. All of the models are trending closer and closer toward closing off a secondary surface low somewhere between Little Rock, AR and Clarksville, TN in response to this second upper-level disturbance. However, even without them actually showing a closed off surface low yet, pressure falls extend down the cold front and surface winds are almost due south beneath the southwesterly (but with trajectories still off the Gulf of Mexico, unlike last week) low-level jet that very rapidly intensifies after dark. So, while the main surface low goes northward into the Great Lakes... another very potent disturbance approaches our area by late afternoon and evening, and we have shear profiles rapidly ramp up toward dark, with deep-layer shear vectors of 60+ kts and almost due west to east... strongly favoring discrete supercells.

For those of you worried about that main surface low ejecting to the northeast... on November 10, 2002, the main surface low was in southern Canada that morning... with south-southwest surface winds over the warm sector down here... but we had pressure falls down the cold front and a second jet streak come out of AR/LA into TN... and we had major tornadoes down here in MS/AL (with SSW sfc winds and only a 40 kt 850mb jet... and 1 km SRH values around what the NAM is progging them to be, and we know how the NAM almost always underplays the low-level shear this far out). Also, the Candlestick Park F5 tornado in MS in March 1966.... the surface low with that event... was in central South Dakota. If we get a secondary surface low or even pressure falls down the cold front, it's not going to matter where the first surface low is... with that new upper-level disturbance and second low-level jet max coming through.

I have a feeling that some people may be significantly caught off-guard by the Mississippi-Alabama-Georgia portion of this threat for late Friday afternoon through early Saturday morning.....

The new GFS is actually showing what you are talking about with secondary surface low development along the front from eastern AR moving into middle TN Friday evening. While I continue to have some concerns about the fact that the 500 mb system is lagging the front so much, I agree that I think the impressive moisture/instability will allow development with subtle forcing, and the jet support looks to increase from late Friday afternoon into Friday night across MS/AL. Could very well be looking at a dipole kind of event where you get a primary max of severe over the Ohio Valley and a secondary max over MS/AL/GA with a "relative" min in between.

[QVectorman]

The fact that you're not seeing stronger vertical velocities probably means that things are much more likely to stay discrete, instead of lining out. Most supercell tornado events from the MS Valley eastward are associated with a weakly capped environment and very subtle forcing. If those stronger vertical velocities were present, there would likely be either not enough storm spacing and/or a quick transition to linear mode.

No, it means I'm seeing subsidence over those areas in the mid/upper levels from mid/upper level features...therefore updrafts will be impeded/retarded hindering the development of most of the thunderstorms from reaching their maximum potential and reducing the vertical velocity gradient within individual storms reducing the possibility of development of a tornado within said vv gradient. It has nothing to do with caps or them becoming linear or choking each other out. If strong vv's were present through the entire atmosphere the updrafts would be maximized along with the directional shear and a strong vv gradient within each storm and have the ability to produce tornadoes. I was not banking on supercells to produce the tornadoes, so I was not worried about them having to stay discrete. I was focusing on the probability that a squall line could produce a couple tornadoes which would then be more dependent on the individual vv gradients within each cell of the squall line.

[Hoosier]

NAM really bombing this thing. The wind fields are disgusting OV/northward.

[TheWeatherPimp]

If the NAM/Euro solution is anywhere close to being accurate, it is going to be a big day from Illinois into Indiana and Ohio.

[Hoosier]

If the NAM/Euro solution is anywhere close to being accurate, it is going to be a big day from Illinois into Indiana and Ohio.

NAM seems to be alone with its superbomb scenario. Not downplaying the threat on the other runs though.

[Stebo]

If the NAM/Euro solution is anywhere close to being accurate, it is going to be a big day from Illinois into Indiana and Ohio.

Yeah I could see this lasting into the overnight, even as far North as here, Instability doesn't wane too terribly quickly after dark and the wind fields only strengthen the later on you go into the evening/overnight. The NAM would not only depict an active cold front but an active warm front too as it lifts NEward through IN/OH into S MI

[wxsmwhrms]

No, it means I'm seeing subsidence over those areas in the mid/upper levels from mid/upper level features...therefore updrafts will be impeded/retarded hindering the development of most of the thunderstorms from reaching their maximum potential and reducing the vertical velocity gradient within individual storms reducing the possibility of development of a tornado within said vv gradient. It has nothing to do with caps or them becoming linear or choking each other out. If strong vv's were present through the entire atmosphere the updrafts would be maximized along with the directional shear and a strong vv gradient within each storm and have the ability to produce tornadoes. I was not banking on supercells to produce the tornadoes, so I was not worried about them having to stay discrete. I was focusing on the probability that a squall line could produce a couple tornadoes which would then be more dependent on the individual vv gradients within each cell of the squall line.

Trust me, I have been hesitant to get too excited about the southern area because of the potential for the upper support to lag the front. But the 12Z GFS is showing plenty of upward motion from MS into AL and middle TN from late Friday afternoon into Friday night now as the upper jet support gets quite favorable. Looks like a strongly diffluent right entrance region with good ageostrophic response and strong upper divergence across the region. Combine that with as Fred says increasing LLJ response and pretty strong instability could be a pretty good setup in that southern area. GFS is also showing 40-60m 500 mb 12 hour height falls across the region during Friday night. Will be interesting to see the EC, but overall the 00Z run supported this idea although the new GFS seems a bit more robust in the secondary cyclogenesis.

[Hoosier]

This is only a snapshot at one location (Indianapolis) but it shows the model differences. NAM still has a favorable environment for severe weather at 00z Saturday while the GFS has already moved the cold front through.

[SluggerWx]

This is just serious rotation in Eastern Kentucky. This cell just keeps on going....

[Hoosier]

This is just serious rotation in Eastern Kentucky. This cell just keeps on going....

http://www.americanwx.com/bb/index.php/topic/32957-february-28-29-severe-threat/page__st__105

[QVectorman]

Trust me, I have been hesitant to get too excited about the southern area because of the potential for the upper support to lag the front. But the 12Z GFS is showing plenty of upward motion from MS into AL and middle TN from late Friday afternoon into Friday night now as the upper jet support gets quite favorable. Looks like a strongly diffluent right entrance region with good ageostrophic response and strong upper divergence across the region. Combine that with as Fred says increasing LLJ response and pretty strong instability could be a pretty good setup in that southern area. GFS is also showing 40-60m 500 mb 12 hour height falls across the region during Friday night. Will be interesting to see the EC, but overall the 00Z run supported this idea although the new GFS seems a bit more robust in the secondary cyclogenesis.

I was referring to the 0z. 12z GFS is has transferred best lift east of the best thermodynamics and shear in those areas. But there are a few areas they overlap so I would expect some decent wx over cn. tenn and n. miss. based on this prog.