April 26th-30th, 2014 Major Tornado Outbreak

[MidwestChaser]

High risk

 

[janetjanet998]

 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0300 PM CDT SUN APR 27 2014  
 
VALID 272000Z - 281200Z  
   
..THERE IS A HIGH RISK OF SVR TSTMS ACROSS MUCH OF CNTRL AR  
 
   
..THERE IS A MDT RISK OF SVR TSTMS ACROSS MUCH OF AR  
NERN  
TX...FAR ERN OK AND SRN MO...  
 
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF THE MID AND  
LOWER MO VALLEY SWD INTO THE MIDDLE AND LOWER MS VALLEY AND  
ARKLATEX...  
   
..SUMMARY  
 
SEVERE THUNDERSTORMS WILL AFFECT ARKANSAS AND ADJACENT AREAS OF  
SOUTHERN MISSOURI...EASTERN OKLAHOMA...AND EXTREME NORTHEAST TEXAS  
THIS AFTERNOON INTO TONIGHT. THE GREATEST TORNADO RISK WILL BE  
CENTERED ON ARKANSAS...WHERE A FEW STRONG AND LONG-TRACK TORNADOES  
WILL BE POSSIBLE THROUGH TONIGHT. OTHERWISE...A BAND OF SEVERE  
THUNDERSTORMS WILL MOVE ACROSS MISSOURI AND IOWA THIS AFTERNOON WITH  
DAMAGING WINDS...LARGE HAIL...AND A FEW TORNADOES. MORE ISOLATED  
SEVERE STORMS WILL BE POSSIBLE THIS AFTERNOON ACROSS CENTRAL  
NEBRASKA.  
 
...ADDED HIGH RISK TO AR IN ANTICIPATION OF SUPERCELLS FORMING  
UPSTREAM OVER NERN TX AND ERN OK...WHICH WILL MATURE AS THEY MOVE  
INTO AR WHERE BETTER LOW LEVEL SHEAR EXISTS...  
 
MUCH OF AR...FAR NERN TX AND SRN MO STILL APPEARS TO BE THE GREATEST  
THREAT AREA FOR TORNADOES. INSTABILITY AND SHEAR PROFILES WILL  
CONTINUE TO BECOME MORE FAVORABLE THROUGHOUT THE AFTERNOON. VISIBLE  
SATELLITE SHOWS SIGNS OF CU BECOMING GRADUALLY DEEPER WITHIN THE  
LOW-LEVEL MOISTURE AXIS ACROSS NERN TX...SWRN AR AND NRN LA.  
SUPERCELLS WILL EVENTUALLY ERUPT ACROSS THESE AREAS...WITH STRONG  
TORNADOES POSSIBLE AS WELL AS VERY LARGE HAIL.  
   
..NEB  
 
STORMS CONTINUE TO BECOME MORE WIDESPREAD AHEAD OF THE SURFACE LOW  
WHERE HEATING HAS DESTABILIZED THE REGION. STEEP LAPSE RATES AND A  
VORTICITY-RICH ENVIRONMENT WILL CONTINUE TO FAVOR LOW-TOPPED  
SUPERCELLS CAPABLE OF HAIL AND A FEW TORNADOES.  
   
..IA...MO...NERN KS  
 
WHILE SOME MOISTURE REMAINS BEHIND THE INITIAL LINE OF STORMS...IT  
IS UNCLEAR WHETHER ENOUGH DESTABILIZATION WILL OCCUR FOR MORE SEVERE  
STORMS. WILL MAINTAIN A CONDITIONAL SLIGHT RISK IN THE WAKE OF THE  
EARLIER STORMS GIVEN HEATING AND DRYLINE POSITION...BUT THE OVERALL  
SEVERE RISK APPEARS LOW.  
 
..JEWELL.. 04/27/2014  
   
 

[SmokeEater]

And we just went High Risk, you were saying jojo?

[Ground Scouring]

Like others have mentioned that stalled differential heating boundary across AR is something to really watch for the rest of the evening, there will be a significant backing of the winds along it and the low level shear is going to skyrocket along it as well. The real danger with it currently is that is parked very close to Little Rock right now.

The RAP doesn't show much change in the placement of the temperature boundary over the next five hours, so Little Rock may luck out. In fact, with the strongest synoptic forcing displaced over nern AR (away from the strongest buoyancy / instability in swrn AR), this outbreak (fortunately) won't live up to what it could have been in terms of severe tornadoes over a wide swath of AR/srn MO. And I doubt we will see numerous strong tornadoes on a record scale. But High Risk is still justified locally, just not as High of a High. Swrn AR is also a bit more rural than other parts to the NE, fortunately (excepting Texarkana vicinity).

 

I'll be ready to eat crow if I'm wrong, however.

[PSUBlizzicane2007]

I'm glad to see the upgrade to high risk as it is very much warranted... and I imagine later tonight, the next version of watch 97/whatever watch replaces the majority of the portion in Arkansas will be upgraded to PDS especially as the supercells really get going.

[KSWx]

Based on what? Jim Cantore is at the SPC and talked to Greg Carbin who said this doesn't really have the makings of a high risk day.

 

FWIW, he will be talking to Rich Thompson sometime soon.

 

Cantore just confirmed via Rich Thompson that AR is getting a high risk upgrade.

[Stebo]

The RAP doesn't show much change in the placement of the temperature boundary over the next five hours, so Little Rock may luck out. In fact, with the strongest synoptic forcing displaced over nern AR (away from the strongest buoyancy / instability in swrn AR), this outbreak (fortunately) won't live up to what it could have been in terms of severe tornadoes over a wide swath of AR/srn MO. But High Risk is still justified, just not as High of a High.

RAP has been terrible for all events this year and last year. I wouldn't use it with much significance.

[Disc]

janetjanet998, on 27 Apr 2014 - 3:38 PM, said:

SPC will likely upgrade AR area in the 20z outlook

 

You must be able to see into the future. Good call on that one.

[Superstorm93]

Red River cell already producing moderate rotation. Should be tornado warned soon

 

[andyhb]

The RAP doesn't show much change in the placement of the temperature boundary over the next five hours, so Little Rock may luck out. In fact, with the strongest synoptic forcing displaced over nern AR (away from the strongest buoyancy / instability in swrn AR), this outbreak (fortunately) won't live up to what it could have been in terms of severe tornadoes over a wide swath of AR/srn MO. And I doubt we will see numerous strong tornadoes on a record scale. But High Risk is still justified locally, just not as High of a High. Swrn AR is also a bit more rural than other parts to the NE, fortunately (excepting Texarkana vicinity).

 

Little Rock is included in the high risk.

[Superstorm93]

Chasers from OK/TX/AR/LA are all converging on this one. Should make up for the radar hole...

 

[Ground Scouring]

RAP has been terrible for all events this year and last year. I wouldn't use it with much significance.

The NAM also puts most of the strongest synoptic forcing NE of where the temperature gradient is setting up, so no, the RAP is not the only model I'm using to support my statement. And Little Rock is on the northernmost edge of the High Risk, where the chance of its verifying is much more conditional. By the way, having the strongest synoptic forcing displaced from the rich warm sector is not a feature of most High-Risk outbreaks.

[QcSevereWx]

east of LR, nice flat terrain.

[Stebo]

The NAM also puts most of the strongest synoptic forcing NE of where the temperature gradient is setting up, so no, the RAP is not the only model I'm using to support my statement. And Little Rock is on the northernmost edge of the High Risk, where the chance of its verifying is much more conditional.

You don't want strong forcing because then you end up with a linear storm mode. The fact that there isn't strong forcing leads to the credence of cellular storm mode. Look where the strong forcing is, what is the current storm mode there? It is a line of convection.

[tornadotony]

The NAM also puts most of the strongest synoptic forcing NE of where the temperature gradient is setting up, so no, the RAP is not the only model I'm using to support my statement. And Little Rock is on the northernmost edge of the High Risk, where the chance of its verifying is much more conditional. By the way, having the strongest synoptic forcing displaced from the rich warm sector is not a feature of most High-Risk outbreaks.

We're done with model playtime.  There is a powerful developing supercell crossing the Red River and other cells initiating along the dryline.

[SmokeEater]

We're done with model playtime.  There is a powerful developing supercell crossing the Red River and other cells initiating along the dryline.

56,000 feet now...

[tornadotony]

That supercell meso on the Red River really in becoming extremely powerful.  I'd have to think we're < 1hr from tornadoes with it.

[Ground Scouring]

You don't want strong forcing because then you end up with a linear storm mode. The fact that there isn't strong forcing leads to the credence of cellular storm mode. Look where the strong forcing is, what is the current storm mode there? It is a line of convection.

 

We're done with model playtime.  There is a powerful developing supercell crossing the Red River and other cells initiating along the dryline.

Now that I think about it, I think the low-level helicity / instability will be enough to overcome the weaker deep-layer shear later this afternoon and overnight over sern OK / nern TX / srn AR. And I agree that the Red River cell, being nicely placed as it is, is likely to become one of the big players.

[Stebo]

Now that I think about it, I think the low-level helicity / instability will be enough to overcome the weaker deep-layer shear later this afternoon and overnight over sern OK / nern TX / srn AR. And I agree that the Red River cell, being nicely placed as it is, is likely to become one of the big players.

LLJ moves in around sunset that will help boost deep-layer shear. You can already see it showing up on this map, down across LA.

 

[Disc]

Hugo, OK at 84/74 with the lone supercell heading that direction. Another area of convection showing up NW of Antlers, OK

[andyhb]

Now that I think about it, I think the low-level helicity / instability will be enough to overcome the weaker deep-layer shear later this afternoon and overnight over sern OK / nern TX / srn AR. And I agree that the Red River cell, being nicely placed as it is, is likely to become one of the big players.

 

Short range progs have 50-70 kts of effective shear overspreading the region as we move further towards evening, there will be no lack of deep layer shear.

[andyhb]

Strong rotation aloft on the Hugo cell.

[1900hurricane]

Radars out of the DFW area seem to be showing new cells trying to fire just to the east of the Metroplex.

[Disc]

[Thrasher Fan]

Storm just NE of Ong, NE very close to needing a TOR Warning.

[PSUBlizzicane2007]

Of note, KARK 4 has said they will broadcast live once the threat commences  http://www.arkansasmatters.com/home

[OKpowdah]

Hugo, OK at 84/74 with the lone supercell heading that direction. Another area of convection showing up NW of Antlers, OK

 

As in temp/dp? 82/70 at the airport, 78/68 at the mesonet.

[Noxx]

TW #100 incomming for the high risk area!

http://www.spc.noaa.gov/products/watch/ww0100.html

[andyhb]

PDS tornado watch coming in Southern AR likely.

[Disc]

OKpowdah, on 27 Apr 2014 - 4:37 PM, said:

As in temp/dp? 82/70 at the airport, 78/68 at the mesonet.

Yeah, temp/dp. Looks like the placefile I was using just updated right after I posted.