Substantial tornado event, Tuesday 2/28 into Wednesday 2/29

[SmokeEater]

Pretty active pattern coming up, with 2 real shots of severe wx in the next 7 days. 2nd event looks to be in Dixie Alley. Discuss.

DAY 3 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0230 AM CST SUN FEB 26 2012

VALID 281200Z - 291200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS ARKLATEX...ERN OK AND

SERN KS TO WRN MID-SOUTH REGION...

...SYNOPSIS...

STG SHORTWAVE TROUGH...MENTIONED IN DAY-2 OUTLOOK OVER WRN

CONUS...IS FCST TO CONSOLIDATE INTO COMPACT MID-UPPER CYCLONE DURING

FIRST HALF OF DAY-3 PERIOD...WHILE MOVING ENEWD FROM CENTRAL ROCKIES

ACROSS ADJACENT HIGH PLAINS. BY 29/00Z...500-MB CYCLONE SHOULD BE

LOCATED OVER NEB/SD...REACHING IA/MN BORDER REGION BY END OF PERIOD.

TRAILING SHORTWAVE TROUGH IS EXPECTED TO EXTEND SSW OF MID-UPPER

CYCLONE CENTER...AT SOMEWHAT LOWER AMPLITUDE THAN PROGGED BY

PREVIOUS MODEL CYCLES.

AT SFC...DEEPENING CYCLONE WILL EJECT NEWD FROM CENTRAL HIGH PLAINS

TO SRN MN...BECOMING NEARLY STACKED WITH RESPECT TO MID-UPPER LOW BY

END OF PERIOD. ATTACHED COLD FRONT SHOULD MOVE EWD OUT OF

CENTRAL/SRN ROCKIES EARLY IN PERIOD...REACHING ERN KS...CENTRAL OK

AND PERMIAN BASIN REGION OF W TX BY 29/00Z. COLD FRONT SHOULD REACH

CENTRAL/SRN IL...S-CENTRAL AR AND S-CENTRAL TX BY 29/12Z.

SUFFICIENT MOISTURE SHOULD INFUSE WARM SECTOR TO YIELD DRYLINE BY

EARLY AFTERNOON FROM NRN COAHUILA NNEWD TO SWRN OK. THIS BOUNDARY

THEN WILL BE OVERTAKEN BY COLD FRONT FROM N-S THROUGH REMAINDER

PERIOD.

...PORTIONS ARKLATEX...ERN OK AND SERN KS TO WRN MID-SOUTH REGION...

SCATTERED TSTMS SHOULD FORM DURING AFTERNOON/EVENING ALONG/AHEAD OF

SFC COLD FRONT AND NE OF DRYLINE...AS SRN FRINGES OF MOST VIGOROUS

LARGE-SCALE ASCENT OVERLAP INCREASING LOW-LEVEL MOISTURE...WITH SFC

DEW POINTS REACHING 60S F. ACTIVITY MAY GROW UPSCALE WITH

INCREASING COVERAGE IN 29/00Z-29/06Z TIME FRAME. ALTHOUGH SFC FLOW

IS FCST TO VEER WITH TIME AHEAD OF COLD FROPA...SPEED SHEAR SHOULD

BE SUFFICIENT TO SUPPORT ENLARGED LOW-LEVEL HODOGRAPHS. LINEAR AND

SUPERCELLULAR MODES ARE POSSIBLE...WITH FULL SPECTRUM OF SVR

THREATS...MAINLY IN FORM OF WIND AND TORNADO RISK. SVR POTENTIAL

SHOULD DIMINISH GRADUALLY WITH TIME AND WITH NEWD EXTENT AS

CONVECTIVE REGIME MOVES INTO PROGRESSIVELY WEAKER BUOYANCY.

FARTHER NE...TSTMS ARE EXPECTED TO OCCUR IN ZONE OF ELEVATED

LOW-LEVEL WAA OVERNIGHT...MOVING NEWD OVER OH VALLEY REGION. FCST

SOUNDINGS SUGGEST WEAK LAPSE RATES ALOFT WITH ELEVATED MUCAPE AOB

500 J/KG AND EFFECTIVE SHEAR MAGNITUDES IN 30-35 KT

RANGE...PRECLUDING ORGANIZED HAIL THREAT.

...CENTRAL PLAINS...

WIDELY SCATTERED TO SCATTERED AND LOW-TOPPED TSTMS...PERHAPS WITH

SUPERCELL STRUCTURES...ARE POSSIBLE MIDDAY INTO LATE AFTERNOON INVOF

KS/NEB BORDER...IN ZONE OF STG DEEP-LAYER ASCENT. STG COOLING

ALOFT...AND NARROW CORRIDOR OF FAVORABLE SFC THETAE AIDED BY

DIABATIC HEATING...SHOULD WEAKEN CINH AND SUPPORT CONVECTIVE

DEVELOPMENT NEAR FRONTAL ZONE. MLCAPE NEAR 500 J/KG IS

POSSIBLE...WITH ENHANCED LOW-LEVEL SHEAR NEAR BOUNDARY. THREAT

APPEARS TOO CONDITIONAL AND MESOSCALE IN NATURE FOR CATEGORICAL

OUTLOOK ATTM.

..EDWARDS.. 02/26/2012

[JoMo]

Will be watching this closely to see what happens. The GFS is quicker at moving the front through when compared to the Euro/NAM. A slower frontal passage would allow more moisture and instability to gather.

[Jim Martin]

This is the 12z NAM sounding for Paris, Texas valid at 9pm cst Wednesday. I know the STP is overused. However, 8.4 on the STP here has my attention. Plus the winds are clearly changing direction with height.

[brettjrob]

Intriguing setup. My initial reaction over the past 24 hours is that it's being slightly overhyped in some circles. The two primary weaknesses are obvious: first and foremost, the veered low-level flow; and secondarily, the terrible low-level lapse rates which wreck the thermodynamic profile, despite otherwise-decent moisture return for late winter. The area affected Tuesday afternoon/evening is far enough east that you don't always need backed winds all the way up to 850 mb to see tornadic supercells, but I'm not sure I've ever seen them there when even surface winds are SSW. AL or MS, yeah, but not E OK or even W AR/MO. If surface winds verify more SSE, then I could see talking about a decent low-CAPE/high-shear supercell event over NE TX into the Ozarks. Keeping an eye on it for now.

[JoMo]

Intriguing setup. My initial reaction over the past 24 hours is that it's being slightly overhyped in some circles. The two primary weaknesses are obvious: first and foremost, the veered low-level flow; and secondarily, the terrible low-level lapse rates which wreck the thermodynamic profile, despite otherwise-decent moisture return for late winter. The area affected Tuesday afternoon/evening is far enough east that you don't always need backed winds all the way up to 850 mb to see tornadic supercells, but I'm not sure I've ever seen them there when even surface winds are SSW. AL or MS, yeah, but not E OK or even W AR/MO. If surface winds verify more SSE, then I could see talking about a decent low-CAPE/high-shear supercell event over NE TX into the Ozarks. Keeping an eye on it for now.

I haven't looked at the 18z but I smelled more of a squall line threat with the cold front and dry mid-level air. The only place that looked interesting for a tornado threat was over NW AR and points south where winds looked like they were more southerly.

[Chicago Storm]

Intriguing setup. My initial reaction over the past 24 hours is that it's being slightly overhyped in some circles. The two primary weaknesses are obvious: first and foremost, the veered low-level flow; and secondarily, the terrible low-level lapse rates which wreck the thermodynamic profile, despite otherwise-decent moisture return for late winter. The area affected Tuesday afternoon/evening is far enough east that you don't always need backed winds all the way up to 850 mb to see tornadic supercells, but I'm not sure I've ever seen them there when even surface winds are SSW. AL or MS, yeah, but not E OK or even W AR/MO. If surface winds verify more SSE, then I could see talking about a decent low-CAPE/high-shear supercell event over NE TX into the Ozarks. Keeping an eye on it for now.

This.

I have been watching the potential for several days now, but there has yet to be anything that looks worth the drive.

[Jim Martin]

0z NAM sounding for Paris TX at 9pm cst Tuesday evening. That one kilometer helicity is staggering to say the least...

[NrnILStormChaser]

:EDIT: Crap the image came out like garbage... here is the link http://beta.wxcaster...&STATIONID=kict

Better cooling aloft sneaks in throughout the afternoon, good speed and directional shear, but shallow moisture and meager instability have me questioning the risk up on the "northern" play of this system. I've liked southeast KS into SC NE all along but haven't really seen anything to make me want to jump at this one.

[Ozarkwx]

@TedKeller (KOLR 10 in SGF) had a good livestream discussion on the threat. He is thinking that the greatest threat is further south over eastern TX and SW AR and NE toward central AR, with a more brief window further north, and decreasing north of the AR border. My sense is that he was not overly impressed, but was worth keeping a close watch on. Indicated he would do another broadcast around 830pm Monday, he will post the link on Twitter.

[JoMo]

New Day 2.

DAY 2 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1256 AM CST MON FEB 27 2012

VALID 281200Z - 291200Z

...THERE IS A SLGT RISK OF SVR TSTMS MAINLY EVENING AND

OVERNIGHT...PORTIONS ERN OK/NE TX TO LOWER OH VALLEY AND

MID-SOUTH...

...THERE IS A SLGT RISK OF SVR TSTMS -- AFTERNOON...PORTIONS NRN KS

AND SRN NEB...

...SYNOPSIS...

ACTIVE UPPER-AIR PATTERN WILL CHARACTERIZE WRN/NRN CONUS THROUGH

PERIOD. MOISTURE CHANNEL IMAGERY ATTM INDICATES TWO SHORTWAVE

TROUGHS/VORTICITY MAXIMA -- OVER COASTAL PAC NW AND OFFSHORE CENTRAL

CA. THESE RELATIVELY LOW-AMPLITUDE FEATURES SHOULD PHASE DAY-1 AND

MOVE INLAND. BY 28/12Z...HIGH-AMPLITUDE SHORTWAVE TROUGH WILL

RESULT OVER GREAT BASIN...PERHAPS WITH EMBEDDED 500-MB LOW OVER

UT/NRN AZ. AS UPSTREAM TROUGH NOW OVER BERING SEA MOVES SEWD AND

INLAND PAC NW...GREAT BASIN TROUGH/LOW WILL EJECT ENEWD ACROSS

CENTRAL ROCKIES/PLAINS. 500-MB LOW SHOULD REACH VICINITY IA/MN

BORDER BY 29/12Z...WITH TROUGH SSWWD ACROSS WRN IA AND CENTRAL/ERN

KS.

AT SFC...STG LEE-SIDE LOW SHOULD DEVELOP BY 28/18Z OVER NERN CO/NEB

PANHANDLE REGION...WITH PAC COLD FRONT SSWWD ACROSS ERN PORTIONS

CO/NM. LOW WILL DEEPEN AND MOVE ENEWD TO BE NEARLY STACKED BENEATH

MIDLEVEL CYCLONE CENTER BY END OF PERIOD. COLD FRONT WILL MOVE EWD

ACROSS SRN HIGH PLAINS...WRN/CENTRAL KS AND MUCH OF WRN OK INTO

EARLY EVENING...OVERTAKING PRE-EXISTING DRYLINE FROM N-S OVER SWRN

OK AND W-CENTRAL/SW TX. BY END OF PERIOD...COLD FRONT SHOULD EXTEND

FROM WRN IL ACROSS SERN MO...WRN AR...AND CENTRAL TX.

MEANWHILE...WARM FRONT INITIALLY MAY BE DIFFUSED BY

PRECIP/CONVECTION OVER ARKLATEX AND SRN PLAINS EARLY IN PERIOD...BUT

WILL BECOME MORE SHARPLY DEFINED WITH TIME. WARM FRONT SHOULD MOVE

NEWD ACROSS LOWER MO VALLEY AND LOWER OH VALLEY...REACHING PORTIONS

OH/INDIANA/NRN IL BY 29/12Z.

...ERN OK/NE TX TO LOWER OH VALLEY AND MID-SOUTH...

SVR THREAT FCST TO INCREASE FROM LATE AFTERNOON THROUGH EVENING OVER

THIS REGION...WITH MOISTURE...BUOYANCY...AND SHEAR ALL BECOMING

FAVORABLE. SUPERCELLS AND QUASI-LINEAR STRUCTURES EACH MAY

OCCUR...WITH DAMAGING GUSTS...TORNADOES AND OCNL LARGE HAIL ALL

POSSIBLE. MOISTURE RETURN BY EVENING SHOULD BE AT LEAST MRGLLY

SUFFICIENT WITH SFC DEW POINTS COMMONLY IN LOW 60S OVER ERN OK AND

AR...MID 60S NEAR RED RIVER. THIS WILL SUPPORT SFC-BASED EFFECTIVE

LIFTED PARCELS IN FCST SOUNDINGS...WITH PREFRONTAL CORRIDOR OF

MLCAPE 500-1000 J/KG. LLJ-ENHANCED HODOGRAPHS YIELD EFFECTIVE SRH

COMMONLY IN 300-500 J/KG RANGE...AMIDST 45-55 KT EFFECTIVE SHEAR

MAGNITUDES. REGIME SHOULD SHIFT ENEWD OVERNIGHT...AS SFC DEW POINTS

REACH MID-50S F TO NEAR 60 OVER PORTIONS WRN KY/SERN MO/SRN IL.

INFLOW AIR MASS SHOULD BE CHARACTERIZED BY NARROWING CORRIDOR OF

FAVORABLE BUOYANCY WITH TIME...AS TSTM AREA SLOWLY OUTPACES REGIME

OF FAVORABLY STG WARM-SECTOR THETAE ADVECTION FROM N-S.

MAIN UNCERTAINTY ATTM INVOLVES CONVECTIVE

INITIATION/COVERAGE...ESPECIALLY WITH SEWD EXTENT TOWARD SRN AR AND

NWRN MS...AND SWD ACROSS RED RIVER REGION INTO TX. ALTHOUGH BROAD

SWATH FROM CENTRAL TX TO PORTIONS WRN KY/WRN TN COULD EXPERIENCE AT

LEAST A FEW HOURS OF VERY FAVORABLE PARAMETER SPACE FOR

SVR...CONSIDERABLE INCONSISTENCIES STILL ARE EVIDENT IN CONVECTIVE

PROGS OVER THIS AREA...ESPECIALLY BEFORE ABOUT 06Z. THIS FACTOR

PRECLUDES GREATER OR MORE TIGHTLY FOCUSED PROBABILITIES ATTM.

....CENTRAL PLAINS...

WIDELY SCATTERED TO SCATTERED TSTMS ARE EXPECTED TO DEVELOP DURING

18-00Z TIME FRAME INVOF SFC LOW...AND TO ITS ESE AND SE IN NARROW

SLIVER OF AT LEAST MRGLLY FAVORABLE BOUNDARY-LAYER THETAE. SVR HAIL

IS LIKELY...ALONG WITH ISOLATED DAMAGING GUSTS. A FEW

MINI-SUPERCELLS ARE POSSIBLE WITH ACCOMPANYING TORNADO RISK AS WELL.

SVR THREAT SHOULD DIMINISH AFTER ABOUT 00Z.

ACTIVITY SHOULD BE LOW-TOPPED...IN ENVIRONMENT OF STEEP LOW-MIDDLE

LEVEL LAPSE RATES AUGMENTED BY CHANNEL OF INSOLATION AFFECTING WARM

SECTOR...JUST AHEAD OF BOTH PAC COLD FRONT AND LOW-MIDDLE LEVEL DRY

SLOT. SFC DEW POINTS ONLY MAY REACH LOW-MIDDLE 40S F OVER WRN

PORTIONS OUTLOOK AREA...ON HIGHER TERRAIN...AND UPPER 40S TO LOW 50S

AT LOWER ELEVATIONS OF S-CENTRAL NEB AND N-CENTRAL KS. STILL...FCST

SOUNDINGS SUGGEST THIS SHOULD BE SUFFICIENT TO SUPPORT WEAK TO NO

CINH BENEATH MLCAPE 200-500 J/KG. WARM SECTOR NEAR LOW WILL BE

CHARACTERIZED BY STG LOW-LEVEL SHEAR...WITH CURVING HODOGRAPHS AND

EFFECTIVE SRH AROUND 300 J/KG.

[Jim Martin]

12z NAM sounding for my target area tomorrow night (Paris TX). 1km Helicity is unreal. Winds are obviously changing with heights. I know the Significant Tornado Parameter is overused. However, a 9.2 Significant Tornado Parameter can not be ignored in this instance.

[tornadotony]

The greatest threat tomorrow is actually going to be after sundown in the Ozarks. During the afternoon/early evening, the lapse rates are going to suck over the plains, to be kind. After 00z, lapse rates in the warm sector begin to steepen, and I think potential for wind/tornadoes will rise.

[JoMo]

There's quite a bit of difference in instability between the NAM/GFS. NAM has been pretty persistent for a squall line around these parts. The greatest tornado risk still looks like it would be across NW Ark and points south due to the winds staying more southerly for longer.

[scoresman]

Latest day 2 from the SPC has shifted the 30% a little further east putting the top 1/2 of Arkansas in the bulls-eye. From a chasing perspective think ill pass on this event and go after Friday instead. Somewhat better chasing terrain and closer to home (Memphis).....

[JoMo]

Springfield AFD:

ONE INTERESTING SCENARIO THAT THE 12Z NAM

DEPICTED WAS THE DEVELOPMENT OF A LOW LEVEL CONVERGENCE

ZONE/TROUGH ACROSS EASTERN OKLAHOMA IN THE AFTERNOON. THE NAM THEN

SHIFTS THIS TROUGH INTO SOUTHWESTERN MISSOURI BY SUNSET. IF THIS

TROUGH MATERIALIZES AND WE SEE BREAKS IN THE CLOUD COVER ACROSS

THIS AREA...THERE WOULD BE A SMALL WINDOW OF OPPORTUNITY FOR

SURFACE BASED SUPERCELL DEVELOPMENT. THIS WILL BE MORE OF A SHORT

TERM FORECAST SCENARIO.

AS WE HEAD INTO TUESDAY NIGHT...A SHARP DRY LINE WILL BEGIN TO

ACCELERATE OUT OF CENTRAL KANSAS AND WESTERN OKLAHOMA AS THAT

UPPER LEVEL ENERGY PIVOTS NORTHEAST THROUGH THE CENTRAL PLAINS.

ALL INDICATIONS ARE THAT FORCING ALONG THE DRY LINE AND MID LEVEL

COOLING SHOULD RESULT IN CONVECTIVE INITIATION EITHER LATE TUESDAY

AFTERNOON OR EARLY TUESDAY EVENING TO OUR WEST. EXACT TIMING OF

ACTUAL INITIATION IS A TOUGH CALL GIVEN WHAT SHOULD BE AN ELEVATED

MIXED LAYER OVERSPREADING THE AREA. ONCE THE STORMS DO

DEVELOP...THE ACCELERATING NATURE OF THE DRY LINE SHOULD RESULT IN

THESE STORMS BECOMING LINEAR IN NATURE AS THEY APPROACH THE

MISSOURI OZARKS. ENOUGH INSTABILITY AND LARGE SCALE SHEAR WILL

BE PRESENT FOR A STRONG TO SEVERE THREAT WITH THIS LINE. THE MAIN

THREAT WILL BE DAMAGING STRAIGHT LINE WINDS. HOWEVER...CAPE AND

SHEAR PROFILES IN THE LOWER THREE KILOMETERS OF THE ATMOSPHERE

WILL ALSO SUPPORT THE GENESIS OF MESOVORTICES ALONG THE LINE. HAVE

THEREFORE INCLUDED A LIMITED THREAT FOR SPIN-UPS IN THE HAZARDOUS

WEATHER OUTLOOK.

Little Rock, AFD:

AS SURFACE LOW MOVES EAST/NORTHEAST DURING THE AFTERNOON

HOURS...LIFT WILL INCREASE ACROSS THE AREA AND WILL HELP TO BREAK

THE CAP OVER THE STATE. THE WIND ENERGY WITH THIS SYSTEM IS

STRONG...BOTH WITH THE LOW LEVEL JET SETTING UP AND WITH SHEAR

CHARACTERISTICS NEAR THE SURFACE...WITH DAMAGING WINDS AND ISOLATED

TORNADOES POSSIBLE. THE MAIN CONCERN WILL BE A LINE OF STORMS

SETTING UP WITH DAMAGING WINDS MOVING THROUGH...BUT THE ISOLATED

TORNADO THREAT CAN NOT BE RULED OUT.

[JoMo]

Still seeing those backing winds across NW Arkansas and SE OK

[David Reimer]

The 21Z SREF and 0Z NAM have my concern level increasing about a fairly substantial severe weather threat after dark tomorrow evening in Southeast Oklahoma and Northeast Texas. Compared to previous runs, the SREF has been increasing the probability of precipitation ongoing along the dryline by 6 PM in Southern Oklahoma I honestly don't see that happening right now, but since ground moisture is fairly abundant at the moment, I'm a little concerned that a system that would have had a cap bust last year may have just enough punch this year, with the added moisture, to get a storm going. If we get a storm to form off the dryline in Southern Oklahoma or North Texas tomorrow afternoon, I could see them being very potent supercells with a fairly substantial severe weather threat.

Honestly, I'm not betting on convection forming along the dryline tomorrow afternoon. If we do get storms to form in Southern Oklahoma and North Texas, they'll most likely end up forming once the cold front/dryline combo begin to move east between the 9 PM - 12 AM hours. The SREF and NAM are both indicating thunderstorms will develop along the cold front as it moves southeast. Obviously any type of linear complex will primarily present a damaging straight-line wind threat, but these EHI numbers are concerning to me.

These are not the 0-1 KM EHI values, but these are still quite significant and would suggest a fairly substantial severe weather threat. The 0Z NAM has brought up instability values and keeps them impressive (for a cool season event) well into the overnight hours. In addition, it's positioned further west then what was shown yesterday. Unlike past years where I didn't have to really care about the severe weather threat besides a chasing standpoint, I have built up a pretty large following that count on the Texas Storm Chasers severe weather coverage, so I have to be concerned about that. The setup is becoming more concerning to me. I'm not going overboard or anything, but my concern level has increased.

[Chicago Storm]

..SRN PLAINS/OZARKS/MID MS VALLEY

AN UPPER-LEVEL TROUGH WILL MOVE QUICKLY ENEWD ACROSS THE FOUR

CORNERS REGION TODAY. THE THROUGH WILL BECOME NEGATIVELY-TILTED AND

CLOSE-OFF OVER THE CNTRL HIGH PLAINS LATE THIS AFTERNOON. IN THE

BASE OF THE UPPER-LEVEL TROUGH...AN IMPRESSIVE 90 TO 110 KT

MID-LEVEL JET WILL MOVE NEWD ACROSS THE SRN AND CNTRL HIGH PLAINS.

THE AIRMASS SHOULD REMAIN CAPPED FROM THE MID-LEVEL JET SWD IN THE

AFTERNOON. HOWEVER...MODEL FORECASTS INITIATE ISOLATED TO SCATTERED

THUNDERSTORMS ALONG A WELL-DEFINED DRYLINE FROM CNTRL KS SWD INTO

WCNTRL OK AND NW TX BY EARLY EVENING. FURTHER TO THE EAST ALONG THE

AXIS OF A BROAD LOW-LEVEL JET...SCATTERED TO NUMEROUS THUNDERSTORMS

SHOULD DEVELOP BY LATE EVENING FROM CNTRL MO SSWWD ACROSS AR INTO

ERN OK AND NE TX. EVENTUALLY...A LARGE LINEAR MCS SHOULD ORGANIZE

DURING THE OVERNIGHT PERIOD MOVING EWD INTO THE MID-MS VALLEY.

THE MID-LEVEL JET WILL CREATE A STRONGLY SHEARED ENVIRONMENT FROM

THE SRN PLAINS EWD ACROSS THE OZARKS AND MID MS VALLEY. FORECAST

SOUNDINGS ACROSS THE REGION THIS EVENING GENERALLY SHOW 0-6 KM SHEAR

VALUES RANGING FROM 90 KT NEAR THE CORE OF THE MID-LEVEL JET IN ERN

KS TO AROUND 65 KT IN THE SRN OZARKS. THIS SHEAR ENVIRONMENT SHOULD

SUPPORT A SEVERE THREAT ACROSS A LARGE AREA TUESDAY EVENING.

INITIALLY...STRONG THUNDERSTORMS WILL BE POSSIBLE ALONG THE DRYLINE

FROM CNTRL KS SWD INTO WCNTRL OK WHERE THE PRIMARY THREAT SHOULD BE

HAIL. HOWEVER...THE GREATER SEVERE THREAT SHOULD EXIST AS STORM

COVERAGE RAPIDLY INCREASES DURING THE EVENING ACROSS ERN PORTIONS OF

THE SRN PLAINS ALONG THE WRN EDGE OF THE LOW-LEVEL JET. THE

STRONGEST LOW-LEVEL SHEAR IS FORECAST TO EXIST FROM ERN OK ENEWD

ACROSS NCNTRL AR AND SE MO WHERE A TORNADO THREAT SHOULD DEVELOP

DURING THE EVENING. FORECAST SOUNDINGS TO THE NORTHEAST OF LITTLE

ROCK AT 03Z TO 06Z HAVE 0-3 KM STORM RELATIVE HELICITIES OF 450 TO

550 M2/S2 WITH MLCAPE VALUES APPROACHING 1000 J/KG. THIS ENVIRONMENT

SHOULD BE SUFFICIENT FOR SUPERCELLS AND TORNADOES. IF A POCKET OF

MODERATE INSTABILITY CAN DEVELOP IN WCNTRL AR AS IS SUGGESTED BY

SOME OF THE MODELS...THEN THE MORE DOMINANT DISCRETE SUPERCELLS

COULD HAVE AN ISOLATED STRONG TORNADO THREAT. SUPERCELLS SHOULD ALSO

BE CAPABLE OF PRODUCING LARGE HAIL AND WIND DAMAGE. IF A LINEAR MCS

CAN ORGANIZE ACROSS AR AND SRN MO AS MANY OF THE MODELS

SUGGEST...THEN THE WIND DAMAGE THREAT COULD BECOME ENHANCED. A WIND

DAMAGE THREAT WILL BE POSSIBLE LATE IN THE PERIOD AS FAR EAST AS WRN

TN AND WRN KY AS THE MCS CROSSES THE MS RIVER.

..NRN KS/SRN-ERN NEB/WRN IA/FAR NW MO

AN UPPER-LEVEL TROUGH WILL MOVE INTO THE CNTRL PLAINS TODAY AS AN

UPPER-LEVEL LOW CLOSES OFF OVER SW SD AND NRN NEB. THUNDERSTORMS

WILL LIKELY DEVELOP JUST AHEAD OF THE UPPER-LEVEL SYSTEM IN THE EXIT

REGION OF THE MID-LEVEL JET THIS AFTERNOON ACROSS SRN NEB AND NRN

KS. THIS ACTIVITY SHOULD SPREAD NEWD INTO THE OMAHA AREA EARLY THIS

EVENING. FORECAST SOUNDINGS FROM NEAR KEARNEY NEB ENEWD TO NEAR

OMAHA AT 00Z HAVE SBCAPE VALUES AROUND 1000 J/KG WITH 75 KT OF DEEP

LAYER SHEAR AND MID-LEVEL LAPSE RATES AROUND 7.5 C/KM. THIS SHOULD

BE SUFFICIENT FOR A LARGE HAIL THREAT.

[andyhb]

[tornadotony]

I'm gonna be honest...I don't at all understand the placing of the 10% area. I would have one in the outlook, but it would be ern OK/wrn AR, not where it's at now.

[andyhb]

I'm gonna be honest...I don't at all understand the placing of the 10% area. I would have one in the outlook, but it would be ern OK/wrn AR, not where it's at now.

I'm inclined to agree.

[JoMo]

I'm gonna be honest...I don't at all understand the placing of the 10% area. I would have one in the outlook, but it would be ern OK/wrn AR, not where it's at now.

I'm also a bit confused by that.

[FSMweather]

I agree completely.Especialy with this mentioned in the outlook. I'm not holding to much hope of seeing much here in Fort Smith. But hopefully we will get some decent action here.

"IF A POCKET OF

MODERATE INSTABILITY CAN DEVELOP IN WCNTRL AR AS IS SUGGESTED BY

SOME OF THE MODELS...THEN THE MORE DOMINANT DISCRETE SUPERCELLS

COULD HAVE AN ISOLATED STRONG TORNADO THREAT"

[NrnILStormChaser]

I'm gonna be honest...I don't at all understand the placing of the 10% area. I would have one in the outlook, but it would be ern OK/wrn AR, not where it's at now.

Without looking to much into it tonight, I would have been more inclined to believe this was placed based on the fact of a pretty powerful MCS with LEWP tornadoes. I would assume their confidence on that was pretty high, but I suppose given the dynamics a dominant supercell or two may produce a couple of tornadoes well out ahead of the line. The first thing I thought though was LEWP

[tornadotony]

Without looking to much into it tonight, I would have been more inclined to believe this was placed based on the fact of a pretty powerful MCS with LEWP tornadoes. I would assume their confidence on that was pretty high, but I suppose given the dynamics a dominant supercell or two may produce a couple of tornadoes well out ahead of the line. The first thing I thought though was LEWP

It's quite possible, and that's basically the only explanation I could even venture. It still seems off. I don't know if we have the skill to pinpoint such a small area like that 24h out accurately for that conditional of an event. Oh well.

[NrnILStormChaser]

It's quite possible, and that's basically the only explanation I could even venture. It still seems off. I don't know if we have the skill to pinpoint such a small area like that 24h out accurately for that conditional of an event. Oh well.

Yeah, I honestly have not looked into the warm sector once with this system due to the fact that I had no desire chasing it. I was more "gung-ho" about the sfc low/triple point but that doesn't look the greatest either. I remember reading a couple AFD's from the area down there talking about spin ups and such so when I took a peak at the TOR risk I just attributed that to the possibility of supercells producing a rogue strong tornado or the probability of a potent squall line producing spin ups every so often. Most people see a 10% risk and automatically assume it is a tornado outbreak with discrete supercells (not saying you thought this at all) but I have seen on a number of occasions the SPC will throw out a 10% for a squall line and/or derecho event.... even though I don't think we will see anything close to that tomorrow. As you said, the predictability isn't that advanced yet, but hey they are the paid experts, not me. It is what it is.

[JoMo]

Eh.

[tornadotony]

06z NAM coming in with 0-1km EHI >3 in the Ouachitas of eastern OK at 06z tomorrow night, with no CINH or cap in place and with a sim ref reflection. Ouch.

[JoMo]

7 AM update pulled the tornado risk back to the SW a bit.

[JoMo]

And the new Day 1 just issued.

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1016 AM CST TUE FEB 28 2012

VALID 281630Z - 291200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF THE CENTRAL

PLAINS INTO THE MID MS VALLEY...

WATER VAPOR LOOPS SHOW AN IMPRESSIVE SHORTWAVE TROUGH OVER THE FOUR

CORNERS REGION. THIS FEATURE WILL EJECT QUICKLY NORTHEASTWARD INTO

THE CENTRAL HIGH PLAINS BY EVENING...AND INTO THE UPPER MS VALLEY BY

29/12Z. MEANWHILE...AN INCREASINGLY STRONG SOUTHERLY LOW LEVEL JET

WILL AFFECT THE SOUTHERN PLAINS AND LOWER MS VALLEY...DRAWING GULF

MOISTURE RAPIDLY NORTHWARD. THE CONDITIONS WILL BECOME FAVORABLE

FOR MULTIPLE AREAS OF POTENTIAL SEVERE WEATHER DURING THIS FORECAST

PERIOD.

...NEB/KS AFTERNOON AND EVENING...

CONDITIONS ACROSS NEB/KS ARE STARTING COLD AND DRY...WITH

TEMPERATURES ONLY IN THE 30S/40S. HOWEVER...RAPID MODIFICATION OF

THE LOW LEVEL AIR MASS IS EXPECTED THIS AFTERNOON AS SOUTHERLY LOW

LEVEL WINDS AND WARMING TEMPERATURES ABOVE THE SURFACE HELP TO ERODE

THE CLOUDS AND TRANSPORT MOISTURE INTO REGION. BY LATE

AFTERNOON...DEWPOINTS NEAR 50F ARE EXPECTED INTO SOUTHERN NEB ALONG

WITH AT LEAST MARGINAL CAPE. STRONG DYNAMIC FORCING WILL ARRIVE

ACROSS WESTERN NEB AND NORTHWEST KS BEFORE DARK...SETTING THE STAGE

FOR SCATTERED LOW-TOPPED THUNDERSTORMS. STRONG WIND FIELDS AND

STEEP LAPSE RATES SUGGEST A RISK OF A FEW STRONG/SEVERE STORMS

CAPABLE OF HAIL AND DAMAGING WINDS. EASTWARD EXTENT OF THESE STORMS

IS UNCERTAIN DUE TO DECREASING INSTABILITY ACROSS EASTERN NEB/IA.

HOWEVER...STRENGTH OF UPPER SYSTEM SUGGESTS AT LEAST SOME THREAT OF

MAINTAINING THE SEVERE THREAT AT LEAST TO THE MO RIVER.

...KS/OK/MO THIS EVENING...

MID LEVEL CAPPING IS LIKELY TO LIMIT CONVECTIVE DEVELOPMENT ACROSS

THE SOUTHERN PLAINS UNTIL AFTER DARK...WHEN THE SURFACE COLD FRONT

BEGINS TO SAG SOUTHEASTWARD INTO THE DEEPER MOISTURE PROFILES OVER

CENTRAL KS/OK. MULTIPLE MODEL SOLUTIONS SUGGEST THUNDERSTORMS WILL

FORM FIRST IN CENTRAL KS AND BUILD SOUTHWARD ALONG THE FRONT INTO

OK...THEN SPREAD EASTWARD INTO PARTS OF MO/AR DURING THE EVENING.

FAVORABLE WIND FIELDS AND STEEPENING LAPSE RATES WILL SUPPORT A RISK

OF SEVERE STORMS CAPABLE OF HAIL AND DAMAGING WINDS. IF DISCRETE

STORMS CAN FORM AHEAD OF THE FRONT...LOW LEVEL HODOGRAPHS ALSO

SUPPORT A RISK OF TORNADIC SUPERCELLS.

...MID MS VALLEY OVERNIGHT...

THE INCREASING CONVECTION OVER OK/KS DURING THE EVENING IS EXPECTED

TO CONGEAL ACROSS SOUTHERN MO AND NORTHERN AR AFTER MIDNIGHT. WHILE

THERE IS CONSIDERABLE DIVERSITY BETWEEN MODEL SOLUTIONS REGARDING

HOW THIS CONVECTION EVOLVES...WIND FIELDS WILL BECOME VERY STRONG

OVERNIGHT AND FAVORABLE FOR DAMAGING WINDS AND TORNADOES. LOW LEVEL

MOISTURE WILL ALSO BE INCREASING ALONG THE MS RIVER VALLEY...

INCREASING THE RISK OF BUOYANT SURFACE-BASED PARCELS AS FAR NORTH AS

SOUTHEAST MO/SOUTHERN IL BY 12Z.