April 27-May 6, 2022 | Tornado Outbreak Sequence

[Iceresistance]

12z Canadian still breaks the Cap on Thursday's & Friday's setups.

[ClicheVortex2014]

FWIW, Euro doesn't have capping issues at 0z but instability and shear are weaker than GFS. GFS continues to have a window of opportunity in SE KS from 21z to ~23z for some really nasty supercells. Initiation at 21z is pretty early for the Plains

Good call regarding making this a 'sequence' thread. I knew any break in severe weather would be temporary and we'd return to the same old... but not this quick. With a persistent flow of systems entering the US through the west coast, one of these events has to produce something at some point, somewhere. CIPS analogs likes a Plains-to-Ohio Valley conveyor belt 

 

This follows climatology pretty well. With the exclusion of the Southeast and secondary focus on the Mid-MS Valley/Ohio Valley, it's safe to assume the analogs chosen include a SE high pressure. Don't want to jinx it but I think the Southeast is done with organized severe weather until the Fall. Finally.

 

Edited April 26, 2022 by ClicheVortex2014

[ClicheVortex2014]

18z NAM is similar to GFS in the sense that there's basically no cap at 21z but the cap returns strong at 0z. There's quite the difference in location of greatest parameters though.

Below are some area average soundings. Very strong instability with sufficient shear would mean significant wind/significant hail potential. However, LCL is slightly above 1km which is getting kinda high. If we were to assume NAM is completely right about this and semi-discrete storms are going to develop, I could see a 10% hatched tornado but the LCL is really a limiting factor for anything higher than that.

Edited April 26, 2022 by ClicheVortex2014

[Iceresistance]

I really don't trust the CFSv2, it's showing a May 3rd, 1999 Repeat over Oklahoma. 

[ClicheVortex2014]

OUN and ICT are ramping up wording in their AFDs. Both are mentioning a possible, albeit conditional, high-impact event.

ICT

The chances of developing severe storms increase as we move into
Friday as a wide based western CONUS trough axis approaches the
Rockies. This time, the dry line may bisect portions of central and
south central KS during peak heating. There remains some differences
in the progression of the dryline and trailing cold front between
models. There looks like there will be much better convergence along
the dryline to help convective initiation although once again
there looks to be a strong cap in place over much of the area.
Should storms develop, all severe hazards, potentially
significant, would be possible. A low probability, high impact
event is possible. This period will be watched closely in the
coming days.

OUN

For Friday, a negatively-tilted shortwave trough is progged to
dig into the Central Plains as it begins to close. As this occurs,
a surface low is forecast to deepen and accelerate across Kansas.
Gusty southerly winds are expected Friday afternoon in response
to the strengthening surface low. The trailing dryline will
advance eastward in tandem with the surface low--just west of
Highway 81 by Friday afternoon.

Ahead of the dryline, the environment will be conditionally
favorable for severe thunderstorms. The environment will be
characterized by MLCAPE of 2500 to 3000+ J/kg with effective bulk
shear ~40 to 45 knots, which is sufficient for supercells. Note
that there is some weakness in the wind fields aloft (when
compared to the low-levels) given the track of the trough farther
to the north. Essentially, wind shear is weak above ~3 km. This
may favor more high precipitation (HP) supercells given the weak
storm-relative winds aloft. Nevertheless, enlarged, looping low-
level hodographs will result in a risk of tornadoes with any
supercells.

The risk for severe thunderstorms is conditional. In other words,
the parameters for severe thunderstorms exist, but can only be
realized if storms are able to form. Forecast soundings indicate
there will be a cap present. While the greatest ascent to lift the
cap will be to the north, there might be sufficient lift farther
south with some subtle DPVA (differential positive vorticity
advection) combined with the dryline circulation for convection--
especially given the close proximity of the trough.

Bottom line: Be prepared for severe weather Friday as the
potential for a higher-end severe risk is there *if* the cap
breaks.

West of dryline, critical to extreme fire weather conditions are
forecast as relative humidity values fall to near 10% or lower.
ERC values across the far west (near the 100th meridian) and
northwest Oklahoma are at or above the 90th percentile, so the
fuels remain volatile in this region (given the lack of
rainfall/ongoing drought). A Fire Weather Watch will likely be
needed in subsequent shifts.

Tulsa

The greatest potential for severe weather will occur on Friday
across much of eastern Oklahoma and western Arkansas. However,
the the potential will be conditional in nature. A dry line is
forecast to surge into western/central Oklahoma Friday afternoon/
evening. The airmass in advance of the dry line is forecast to
be strongly capped during this time. Despite the cap, a few
storms may be able to initiate in the vicinity of the dry line
Friday evening as a mid-level shortwave moves across Kansas.
Any storms that do develop will likely become severe with all
modes of severe weather possible as they spread into the area.

 

[ClicheVortex2014]

Great thread from the SPC forecaster who wrote yesterday and todays day 4-8 outlook

 

[Ingyball]

3 hours ago, ClicheVortex2014 said:

18z NAM is similar to GFS in the sense that there's basically no cap at 21z but the cap returns strong at 0z. There's quite the difference in location of greatest parameters though.

Below are some area average soundings. Very strong instability with sufficient shear would mean significant wind/significant hail potential. However, LCL is slightly above 1km which is getting kinda high. If we were to assume NAM is completely right about this and semi-discrete storms are going to develop, I could see a 10% hatched tornado but the LCL is really a limiting factor for anything higher than that.

The Plains seem to be able to produce tornadoes even with higher LCLs around 1km. DDCs 19z sounding on Friday had LCLs around 1500m, not sure if those same LCLs were present in Goodland's area or not though. There is a study that I just looked up that talks about this. I only read the abstract, but it suggest other thermodynamic  processes can overcome high LCLs. Though the cap also needs to be weak it appears as well. https://journals.ametsoc.org/view/journals/wefo/21/4/waf928_1.xml

[Cincysnow]

Often, I need to look up some of the met talk (weather acronyms), and stumbled across this today. A good source of info related to acronyms and the definition of each: 

https://www.weather.gov/source/zhu/ZHU_Training_Page/convective_parameters/Sounding_Stuff/MesoscaleParameters.html

[Ingyball]

11 minutes ago, Cincysnow said:

Often, I need to look up some of the met talk (weather acronyms), and stumbled across this today. A good source of info related to acronyms and the definition of each: 

https://www.weather.gov/source/zhu/ZHU_Training_Page/convective_parameters/Sounding_Stuff/MesoscaleParameters.html

I know on wxdicso they had some of our lingo underlined that gave a brief description, that could be a good thing to add. @Uscg Ast Otherwise I'll try to make it a point to at least spell out the abbreviations going forward.  

[ClicheVortex2014]

NAM is looking a lot like GFS now. At least the supercell composite map does on the surface. Capping issues along most of the dryline at 0z except for N KS/S NE.

 

Cap isn't an issue along the dryline in S KS. What this means to me is that, given forcing, the action would start in N OK/S KS and gradually work north.

Edited April 27, 2022 by ClicheVortex2014

[Cincysnow]

37 minutes ago, Ingyball said:

I know on wxdicso they had some of our lingo underlined that gave a brief description, that could be a good thing to add. @Uscg Ast Otherwise I'll try to make it a point to at least spell out the abbreviations going forward.  

No worries, wasn’t directed at you, just thought others (as well as me) could find the site useful. And yes, I do remember the other site having a brief description of terminology. 

[ClicheVortex2014]

1 hour ago, Cincysnow said:

No worries, wasn’t directed at you, just thought others (as well as me) could find the site useful. And yes, I do remember the other site having a brief description of terminology. 

fwiw, I'm always happy to try to answer questions, too. In the thread or via pm. I began learning by shamelessly asking questions. A goal of mine has been to pay it forward.

Edited April 27, 2022 by ClicheVortex2014

[ClicheVortex2014]

GFS has been ridiculously consistent. Not much of significance has changed. Here's an area average sounding for SE KS. Pretty nasty.

 

Edited April 27, 2022 by ClicheVortex2014

[Sentinel]

1 hour ago, Ingyball said:

I know on wxdicso they had some of our lingo underlined that gave a brief description, that could be a good thing to add. @Uscg Ast Otherwise I'll try to make it a point to at least spell out the abbreviations going forward.  

Will definitely work on this with the crew

[ClicheVortex2014]

Wish there was a better way to compare mlcape with mlcin but this really fares well with previous Euro runs... 21z capped, 0z uncapped. Opposite of GFS.

Another way to look at it is that both models have a window for uninhibited instability.

[ClicheVortex2014]

Day 3 enhanced. Also decent sized hatched severe threat.

DAY 3 CONVECTIVE OUTLOOK    
NWS STORM PREDICTION CENTER NORMAN OK  
0238 AM CDT WED APR 27 2022  
  
VALID 291200Z - 301200Z  
  
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF  
SOUTHEAST NEBRASKA INTO NORTHEAST KANSAS...  
   
..SUMMARY  
  
SEVERE THUNDERSTORMS CAPABLE OF ALL HAZARDS ARE POSSIBLE FRIDAY  
AFTERNOON INTO FRIDAY NIGHT ACROSS PORTIONS OF THE SOUTHERN AND  
CENTRAL PLAINS INTO THE LOWER MISSOURI VALLEY.  
   
..SYNOPSIS  
  
A NEGATIVE-TILT MID/UPPER TROUGH WILL BE CENTERED FROM THE NORTHERN  
INTERMOUNTAIN REGION TO THE SOUTHERN ROCKIES FRIDAY MORNING. THIS  
SYSTEM IS EXPECTED TO SHIFT EAST THROUGH THE PERIOD, EMERGING OVER  
THE PLAINS BY EVENING. AS THIS OCCURS, AN UPPER LOW IS EXPECTED TO  
CLOSE OVER THE CENTRAL PLAINS. THIS WILL FOCUS THE STRONGEST FLOW,  
FORCING FOR ASCENT AND UPPER DIVERGENCE FROM FAR NORTHERN OK INTO KS  
AND NE. AT THE SURFACE, LOW PRESSURE IS FORECAST TO DEEPEN OVER  
WESTERN KS AND SHIFT EAST NEAR THE KS/NE BORDER THROUGH EVENING  
BEFORE LIFTING NORTHEAST TOWARD SOUTHEAST SD OVERNIGHT. A DRYLINE  
WILL EXTEND SOUTHWARD FROM THE LOW ACROSS CENTRAL KS INTO CENTRAL  
OK/TX BY MID-AFTERNOON. MEANWHILE, A WARM FRONT WILL LIFT NORTHWARD  
THROUGH THE PERIOD, EXTENDING FROM THE LOW NEAR CENTRAL NE INTO  
SOUTHERN IA DURING THE AFTERNOON/EVENING. LOW TO MID 60S F SURFACE  
DEWPOINTS (WITH SOME POCKETS OF UPPER 60S F POSSIBLE WITH SOUTHWARD  
EXTENT) WILL RESIDE WITHIN THE WARM SECTOR. A SURFACE COLD FRONT  
WILL SURGE SOUTHEAST DURING THE EVENING/OVERNIGHT, EVENTUALLY  
OVERTAKING THE DRYLINE AND BECOMING POSITIONED FROM SOUTHWEST IA  
INTO WESTERN MO, SOUTHEAST OK AND NORTH-CENTRAL TX BY SATURDAY  
MORNING.   
   
..NE/KS INTO THE LOWER MO VALLEY  
  
FORECAST GUIDANCE INDICATES A STRONG MIDLEVEL CAP WILL ERODE BY LATE  
AFTERNOON AMID INCREASING ASCENT AND LOW-LEVEL MOIST ADVECTION.  
BACKED LOW-LEVEL WINDS NEAR THE TRIPLE POINT WILL RESULT IN ENLARGED  
LOW-LEVEL HODOGRAPHS WITH FORECAST EFFECTIVE SHEAR MAGNITUDES AROUND  
35-45 KT. BACKED LOW-LEVEL FLOW WILL ALSO ENHANCE LOW-LEVEL SHEAR,  
WITH SRH VALUES INCREASING TO GREATER THAN 250 M2/S2. THIS WILL BE  
FAVORABLE FOR ROTATING SUPERCELLS, AND A FEW TORNADOES ARE POSSIBLE.  
VERY STEEP MIDLEVEL LAPSE RATES AND MLCAPE AS HIGH AS 2500 J/KG WILL  
SUPPORT LARGE TO VERY LARGE HAIL. INITIAL SUPERCELL ACTIVITY MAY  
EVENTUALLY GROW INTO CLUSTERS AS THE COLD FRONT SURGES EAST DURING  
THE EVENING, RESULTING IN A POTENTIAL TRANSITION TOWARD DAMAGING  
GUSTS AND HAIL AS CONVECTION SPREADS EAST/NORTHEAST INTO PARTS OF  
THE MO VALLEY.  
   
..OK/TX  
  
A SOMEWHAT MORE CONDITIONAL THREAT WILL EXTEND SOUTHWARD ALONG THE  
DRYLINE INTO OK/TX. FORCING FOR ASCENT WILL BE WEAKER ACROSS THIS  
AREA. ADDITIONALLY, GUIDANCE SUGGEST THE STOUT CAPPING INVERSION  
WILL REMAIN INTACT ACROSS MUCH OF THE AREA THROUGH PEAK HEATING.  
HOWEVER, A NARROW CORRIDOR ALONG THE DRYLINE APPEARS LIKELY TO  
BECOME UNCAPPED DURING THE AFTERNOON AMID STRONG HEATING AND  
INCREASING LOW-LEVEL MOISTURE. IF THESE CELLS DEVELOP, SUPERCELLS  
CAPABLE OF ALL SEVERE HAZARDS WILL BE POSSIBLE ACROSS PARTS OF  
CENTRAL OK INTO NORTHWEST TX. AS THE COLD FRONT DEVELOPS SOUTHEAST  
DURING THE LATE EVENING/OVERNIGHT, ELEVATED STORMS ARE MORE LIKELY  
TO SHIFT EAST ACROSS THE AREA. THIS ACTIVITY WILL MAINLY POSE A RISK  
FOR LARGE HAIL.  

 

[Iceresistance]

Slight Risks through May 2nd now

April 30th - Mississippi & Ohio Rivers

May 1st - Western Texas

May 2nd - Northern Texas, Southern 2/3rd's of Oklahoma, NW Louisiana, & SW Arkansas

[ElectricStorm]

Starting to get more concerned for KS on Fri, wouldn't be surprised to see this end up as a 15 hatched moderate risk day.

Not excited about anything south of there though. Leaning towards a cap bust in OK for now

[Iceresistance]

All the TV Mets I've seen in OKC have Friday as "Severe weather possible, but highly conditional".

[StormfanaticInd]

If the cap does break it could indeed get interesting 

[ElectricStorm]

You know the parameters are going to be bonkers when 5/10 and 5/24 both show up in the analogs...

I think it will be tough to break the cap in OK but so much can change in a couple days we'll still have to watch it. If anything can break it watch out 

https://www.eas.slu.edu/CIPS/ANALOG/DFHR.php?reg=SP&fhr=F072&rundt=2022042700&map=thbSVR

[Iceresistance]

28 minutes ago, OKwx_2001 said:

You know the parameters are going to be bonkers when 5/10 and 5/24 both show up in the analogs...

I think it will be tough to break the cap in OK but so much can change in a couple days we'll still have to watch it. If anything can break it watch out 

https://www.eas.slu.edu/CIPS/ANALOG/DFHR.php?reg=SP&fhr=F072&rundt=2022042700&map=thbSVR

Most of the models have a stronger cap bias, but only the observed soundings will tell the truth on the Cap strength.

[Neoncyclone]

What an absolutely incredible environment the 12 GFS depicts, ridiculous lapse rates to the order of 9.7C in the mid-high levels.....  This run features more bad news, I can pull soundings from random places up and down the dryline and see breach-able caps all along. Hope this doesn't become the trend, but the GFS has been incredibly consistent lately, not just for this setup. 

21z still a largely uncapped environment, so initiation would almost have to start around that time for any substantial threat to unfold as the cap only strengthens as the night goes on according to the GFS anyways.

N OK/S KS border. 

C OK (still has a pretty strong cap)

C KS

 

 

[ElectricStorm]

Slight risk up for today now. Shouldn't be a tornado threat, but could be some gusty winds 

[ClicheVortex2014]

2 hours ago, Neoncyclone said:

What an absolutely incredible environment the 12 GFS depicts, ridiculous lapse rates to the order of 9.7C in the mid-high levels.....  This run features more bad news, I can pull soundings from random places up and down the dryline and see breach-able caps all along. Hope this doesn't become the trend, but the GFS has been incredibly consistent lately, not just for this setup. 

21z still a largely uncapped environment, so initiation would almost have to start around that time for any substantial threat to unfold as the cap only strengthens as the night goes on according to the GFS anyways.

N OK/S KS border. 

C OK (still has a pretty strong cap)

C KS

 

 

That first one... wow. Even the hail core of a hypothetical supercell in that environment would absolutely wreck a car.

Love me a nice dryline. Got a 60 degree dew point gradient on 3km NAM.

 

Edited April 27, 2022 by ClicheVortex2014