March 21-23, 2022 | Tornado Outbreak

[Chinook]

51 minutes ago, OKwx_2001 said:

My guess is we'll see a Day 3 enhanced for Monday. Instability doesn't look like anything crazy right now but that's enough to get the job done and sometimes models underestimate it a bit. As of right now, I'm not really seeing a whole lot holding either Monday or Tuesday back right now but there's still enough time for things to change. Either way both days will likely be pretty big events. 

I agree. The NAM has some large severe weather elements in east Texas. As of right now, the GFS has the higher storm-relative helicity farther east away from the dryline. I would guess that there's some uncertainty associated with that SRH.  I think SPC will go with enhanced risk at some time, probably as of tonight's Day-3 outlook, maybe even an enhanced tornado outlook upcoming at some time. Question: Is the 15% contour valid as an enhanced tornado outlook for Day-1? I forgot.

[ElectricStorm]

21 minutes ago, Chinook said:

I agree. The NAM has some large severe weather elements in east Texas. As of right now, the GFS has the higher storm-relative helicity farther east away from the dryline. I would guess that there's some uncertainty associated with that SRH.  I think SPC will go with enhanced risk at some time, probably as of tonight's Day-3 outlook, maybe even an enhanced tornado outlook upcoming at some time. Question: Is the 15% contour valid as an enhanced tornado outlook for Day-1? I forgot.

They only do the specific tornado probs on the Days 1 and 2 outlooks. Day 3 enhanced would be a 30% general severe risk. 

Part of me wants to stay up for it...

[ElectricStorm]

Day 3 is indeed enhanced 

 

[StormfanaticInd]

Yikes!!!

 

Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Sat Mar 19 2022 Valid 221200Z - 271200Z ...SEVERE WEATHER OUTBREAK POSSIBLE ON D4/TUE... ...DISCUSSION... Latest deterministic and ensemble runs of the medium-range global models continue to depict likelihood of a continuation of potentially substantial severe-weather event across the central Gulf Coast states Tuesday and into Wednesday. This includes a reasonable probability of a regional-type tornado outbreak centered over central and southern Mississippi for Tuesday. As strong upper low/trough over the central and southern Plains region shifts gradually eastward, a belt of very strong mid- and upper-level southwesterlies will likely extend from east Texas across the Tennessee Valley, atop a 60 kt southerly low-level jet. The resulting/anticipated degree of veering and increasing flow with height falls within high-end parameter space for significant tornadoes. In addition, the strong low-level southerlies will persistently advect high theta-e Gulf air (dewpoints averaging in the upper 60s) northward into the pre-frontal warm sector, which -- despite limited heating due to cloud cover and potentially ongoing convection in some areas -- will combine with modestly steep mid-level lapse rates to yield what should prove to be ample CAPE at least as far north as central Mississippi, and later central Alabama. Overall, given very strong shear, the strength of the upper system, and the Gulf warm sector expected inland, a high-end environment appears likely to exist across a geographically-focused area centered over the central Gulf Coast states, supporting potential for a substantial outbreak of severe/supercell storms. Severe weather potential will likely continue into Wednesday, though the upper system appears likely to become somewhat sheared/elongated as the upper low/jet streak shift northeastward across the Ohio Valley, while secondary energy digs southward across the southern Rockies and into northern Mexico. Thus, while an amply moist/unstable environment and still-strong shear will exist across southeastern Alabama/southwestern Georgia/the Florida Panhandle, and possibly expanding during the day into parts of South Carolina supporting continued potential for severe storms, the risk will be lesser than Tuesday's event, and should diminish with time into the evening hours. Still, all-hazards severe weather will be a possibility through the first half of the period across this portion of the Southeast.

[Undertakerson2.0]

 

Representative sounding via Euro. Some elements of loaded gun sounding with that upper level (300mb level and up) increase in temperature (where we'd usually see continually cooling as one goes higher up). This should blow the roof off of any kind of CINH

The SHR (loosely evaluated by the relative position of the green line to the red) appears to suggest significant mixing/shear

Hodograph Critical Angle is a stout enough 69 (50-99 is increasingly worrisome)

Although Surface temps indicate some nullification of the above (it's not super warm)  it is transporting very "soupy" SE flow straight from the GOM, so lifting the parcel will cause havoc. 

This has an outside chance, as things stand right now, to go to PDS level. 

 

 

 

[Iceresistance]

9z SREF has a 60% STP in SE Texas

[ElectricStorm]

SPC flat out mentions tornado outbreak on Tuesday. May be some Day 3 moderate material but it will probably be enhanced. 

[ClicheVortex2014]

Wow I haven’t seen that kind of wording for a day 4 outlook in a very long time 

Edited March 19, 2022 by ClicheVortex2014

[Iceresistance]

1 minute ago, OKwx_2001 said:

SPC flat out mentions tornado outbreak on Tuesday. May be some Day 3 moderate material but it will probably be enhanced. 

This uncontaminated 6z GFS sounding is over SE Mississippi, & it's really scary. O_O

[ClicheVortex2014]

Ok so I'm going to share some day 4 outlooks for previous significant events... keep in mind I'm not saying this event is comparable to any of the events because everything has to happen just right... and they did.

These all turned out to be high risks except for Easter 2020 which easily could've been. They all happen to be high-end events because those are the most memorable... I'm sure there are plenty of examples of events that had very strongly worded day 4 outlooks that turned out to be less threatening.

2011 Super Outbreak

DAY 4-8 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0350 AM CDT SUN APR 24 2011
   
   VALID 271200Z - 021200Z
   
   ...DISCUSSION...
   WIDESPREAD CONVECTIVE/SEVERE WEATHER EVENT -- ONGOING FROM THE DAY 3
   /TUE. 4-26/ PERIOD -- IS LIKELY TO CONTINUE SPREADING EWD ACROSS THE
   OH/TN VALLEYS AND GULF COAST STATES DAY 4 /WED. 4-27/...AS
   MEDIUM-RANGE MODELS BOTH FORECAST EWD PROGRESSION OF THE LARGE
   CENTRAL U.S. TROUGH.  AS THE COLD FRONT SHIFTS EWD TOWARD THE
   APPALACHIANS THROUGH THE AFTERNOON AND EVENING...PRE-FRONTAL WARM
   SECTOR FEATURING MODERATE INSTABILITY AND STRONG DEEP-LAYER SHEAR
   WILL SUPPORT CONTINUATION/REDEVELOPMENT OF SEVERE STORMS INTO THE
   AFTERNOON AND EVENING.  POTENTIAL FOR SUBSTANTIAL SEVERE WEATHER --
   INCLUDING HAIL/WIND AND ISOLATED TORNADOES -- SUPPORTS CONTINUATION
   OF A LARGE SEVERE WEATHER THREAT AREA FOR DAY 4.  

11/17/13

  DAY 4-8 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0400 AM CST THU NOV 14 2013

   VALID 171200Z - 221200Z

   ...DISCUSSION...
   SOME UNCERTAINTY LINGERS...BUT TRENDS IN THE MEDIUM RANGE FORECAST
   GUIDANCE ARE INCREASINGLY SUGGESTIVE OF THE DEVELOPMENT OF AN
   ENVIRONMENT SUPPORTIVE OF AN OUTBREAK OF SEVERE THUNDERSTORMS ACROSS
   PARTS OF THE MIDDLE MISSISSIPPI VALLEY EASTWARD THROUGH MUCH OF THE
   OHIO VALLEY ON SUNDAY.  MOST GUIDANCE NOW APPEARS GENERALLY FASTER
   WITH THE CONTINUED EASTWARD PROGRESSION OF A STRONG SHORT WAVE
   TROUGH...FROM THE CENTRAL PLAINS EARLY SUNDAY TO THE LOWER GREAT
   LAKES/UPPER OHIO VALLEY/CENTRAL APPALACHIANS REGION BY LATE SUNDAY
   NIGHT.  MOST MODELS ARE NOW SUGGESTIVE THAT THIS WILL BE ACCOMPANIED
   BY STRONG SURFACE CYCLOGENESIS...WITH MOST RAPID SURFACE PRESSURE
   FALLS ACROSS PARTS OF THE GREAT LAKES REGION AND OHIO VALLEY LATE
   SUNDAY AFTERNOON INTO SUNDAY NIGHT.  

   A 90+ KT 500 MB JET STREAK NOSING THROUGH THE OHIO VALLEY...COUPLED
   WITH STRENGTHENING SOUTHERLY WARM SECTOR 850 MB FLOW...PERHAPS IN
   EXCESS OF 70 KTS ACROSS PARTS OF THE OHIO VALLEY INTO THE LOWER
   GREAT LAKES...WILL CONTRIBUTE TO VERY STRONG DEEP LAYER WIND FIELDS
   AND SHEAR.  IT ALSO APPEARS INCREASINGLY PROBABLE THAT THIS WILL
   COINCIDE WITH AN INFLUX OF SEASONABLY HIGH MOISTURE CONTENT AT LEAST
   AS FAR NORTH AND EAST AS THE LOWER OHIO VALLEY...CONTRIBUTING TO
   SUFFICIENT CAPE FOR VIGOROUS STORM DEVELOPMENT.  SUPERCELLS WITH A
   RISK FOR TORNADOES WILL BE POSSIBLE...PARTICULARLY IN EARLY STAGES
   OF CONVECTIVE DEVELOPMENT...PERHAPS AS EARLY AS MID DAY ACROSS PARTS
   OF THE MIDDLE MISSISSIPPI INTO LOWER OHIO VALLEY VALLEY.

Easter 2020

 ...D4/Sunday: TX Gulf Coast eastward through the Southeast into the
   Carolinas...
   Ingredients for a potential severe thunderstorm outbreak appear
   likely to come together Sunday into Sunday night. An ejecting
   shortwave trough is forecast to take on a neutral to somewhat
   negative tilt by Sunday afternoon as it moves quickly
   east-northeastward across the Southeast states. Rich low-level
   moisture will be drawn inland from the Gulf of Mexico in advance of
   a deepening surface low that will move from the mid-MS Valley into
   the Ohio Valley by Monday morning. Moderate destabilization in
   conjunction with an 80-100 kt midlevel jet and 50-60 kt low-level
   jet will result in a very favorable environment for organized
   convection, including the potential for long-track supercells and a
   corresponding strong tornado risk. Very strong low/midlevel flow
   fields will also support widespread damaging wind potential. 

   Some uncertainty remains regarding the northward extent of the most
   significant severe potential, given the presence of widespread
   convection in advance of the ejecting shortwave. Guidance also
   continues to trend slightly slower, with the GFS still a notably
   fast outlier. A 30% probability contour has been introduced from LA
   into central/southern MS/AL and southwest GA, where confidence is
   highest in the outbreak potential at this time.

   An organized severe thunderstorm threat will likely continue into
   Monday morning, with the potential for damaging wind and/or a few
   tornadoes likely spreading into portions of the Carolinas by 12Z
   Monday. 

May 20, 2019 which turned into a 45% tornado probability bust because *one thing* didn't verify... that being warm sector convection.

	

   ZCZC SPCSWOD48 ALL
   ACUS48 KWNS 170900
   SPC AC 170900

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0400 AM CDT Fri May 17 2019

   Valid 201200Z - 251200Z

   ...DISCUSSION...
   On D4/Monday, a lead shortwave trough will eject out of the base of
   the deep upper troughing over the western CONUS into the
   central/southern Plains. This lead wave is not expected to be
   particularly deep, with the more significant, deeper shortwave
   lagging back over the Southwest. This leads to the unique situation
   where strong moisture advection and backed surface winds are able to
   persist as a source of lift interacts with the warm sector. Wind
   fields are also impressively strong, with southwesterly 500 mb flow
   approaching 80 kt atop 50 kt 850 mb southerly flow and 20-25 kt
   southeasterly surface winds. The overall result of these factors is
   an environment strongly supportive of severe storms. An initial
   discrete mode capable of all severe hazards, including tornadoes, is
   anticipated. If a discrete mode can be maintained, strong tornadoes
   could occur. Upscale growth is eventually expected, with a strong
   MCS then tracking eastward across OK and adjacent portions of
   southern KS and north TX.

   The evolution of the MCS anticipated on D4/Monday will have a large
   impact on the downstream air mass and resulting severe threat on
   D5/Tuesday. Even so, current guidance shows good consensus that a
   shortwave and accompanying strong flow aloft will interact with a
   warm sector from roughly the MO river valley into the Mid-South.
   Uncertainty regarding cloud cover and resulting effective on diurnal
   heating and the extent of air mass destabilization currently
   preclude enough confidence to introduce a 30% outlook area.

 

Edited March 19, 2022 by ClicheVortex2014

[ClicheVortex2014]

Hodograph porn, anyone?

 

[snowlover2]

1 hour ago, ClicheVortex2014 said:

Ok so I'm going to share some day 4 outlooks for previous significant events... keep in mind I'm not saying this event is comparable to any of the events because everything has to happen just right... and they did.

These all turned out to be high risks except for Easter 2020 which easily could've been. They all happen to be high-end events because those are the most memorable... I'm sure there are plenty of examples of events that had very strongly worded day 4 outlooks that turned out to be less threatening.

2011 Super Outbreak

DAY 4-8 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0350 AM CDT SUN APR 24 2011
   
   VALID 271200Z - 021200Z
   
   ...DISCUSSION...
   WIDESPREAD CONVECTIVE/SEVERE WEATHER EVENT -- ONGOING FROM THE DAY 3
   /TUE. 4-26/ PERIOD -- IS LIKELY TO CONTINUE SPREADING EWD ACROSS THE
   OH/TN VALLEYS AND GULF COAST STATES DAY 4 /WED. 4-27/...AS
   MEDIUM-RANGE MODELS BOTH FORECAST EWD PROGRESSION OF THE LARGE
   CENTRAL U.S. TROUGH.  AS THE COLD FRONT SHIFTS EWD TOWARD THE
   APPALACHIANS THROUGH THE AFTERNOON AND EVENING...PRE-FRONTAL WARM
   SECTOR FEATURING MODERATE INSTABILITY AND STRONG DEEP-LAYER SHEAR
   WILL SUPPORT CONTINUATION/REDEVELOPMENT OF SEVERE STORMS INTO THE
   AFTERNOON AND EVENING.  POTENTIAL FOR SUBSTANTIAL SEVERE WEATHER --
   INCLUDING HAIL/WIND AND ISOLATED TORNADOES -- SUPPORTS CONTINUATION
   OF A LARGE SEVERE WEATHER THREAT AREA FOR DAY 4.  

11/17/13

  DAY 4-8 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0400 AM CST THU NOV 14 2013

   VALID 171200Z - 221200Z

   ...DISCUSSION...
   SOME UNCERTAINTY LINGERS...BUT TRENDS IN THE MEDIUM RANGE FORECAST
   GUIDANCE ARE INCREASINGLY SUGGESTIVE OF THE DEVELOPMENT OF AN
   ENVIRONMENT SUPPORTIVE OF AN OUTBREAK OF SEVERE THUNDERSTORMS ACROSS
   PARTS OF THE MIDDLE MISSISSIPPI VALLEY EASTWARD THROUGH MUCH OF THE
   OHIO VALLEY ON SUNDAY.  MOST GUIDANCE NOW APPEARS GENERALLY FASTER
   WITH THE CONTINUED EASTWARD PROGRESSION OF A STRONG SHORT WAVE
   TROUGH...FROM THE CENTRAL PLAINS EARLY SUNDAY TO THE LOWER GREAT
   LAKES/UPPER OHIO VALLEY/CENTRAL APPALACHIANS REGION BY LATE SUNDAY
   NIGHT.  MOST MODELS ARE NOW SUGGESTIVE THAT THIS WILL BE ACCOMPANIED
   BY STRONG SURFACE CYCLOGENESIS...WITH MOST RAPID SURFACE PRESSURE
   FALLS ACROSS PARTS OF THE GREAT LAKES REGION AND OHIO VALLEY LATE
   SUNDAY AFTERNOON INTO SUNDAY NIGHT.  

   A 90+ KT 500 MB JET STREAK NOSING THROUGH THE OHIO VALLEY...COUPLED
   WITH STRENGTHENING SOUTHERLY WARM SECTOR 850 MB FLOW...PERHAPS IN
   EXCESS OF 70 KTS ACROSS PARTS OF THE OHIO VALLEY INTO THE LOWER
   GREAT LAKES...WILL CONTRIBUTE TO VERY STRONG DEEP LAYER WIND FIELDS
   AND SHEAR.  IT ALSO APPEARS INCREASINGLY PROBABLE THAT THIS WILL
   COINCIDE WITH AN INFLUX OF SEASONABLY HIGH MOISTURE CONTENT AT LEAST
   AS FAR NORTH AND EAST AS THE LOWER OHIO VALLEY...CONTRIBUTING TO
   SUFFICIENT CAPE FOR VIGOROUS STORM DEVELOPMENT.  SUPERCELLS WITH A
   RISK FOR TORNADOES WILL BE POSSIBLE...PARTICULARLY IN EARLY STAGES
   OF CONVECTIVE DEVELOPMENT...PERHAPS AS EARLY AS MID DAY ACROSS PARTS
   OF THE MIDDLE MISSISSIPPI INTO LOWER OHIO VALLEY VALLEY.

Easter 2020

 ...D4/Sunday: TX Gulf Coast eastward through the Southeast into the
   Carolinas...
   Ingredients for a potential severe thunderstorm outbreak appear
   likely to come together Sunday into Sunday night. An ejecting
   shortwave trough is forecast to take on a neutral to somewhat
   negative tilt by Sunday afternoon as it moves quickly
   east-northeastward across the Southeast states. Rich low-level
   moisture will be drawn inland from the Gulf of Mexico in advance of
   a deepening surface low that will move from the mid-MS Valley into
   the Ohio Valley by Monday morning. Moderate destabilization in
   conjunction with an 80-100 kt midlevel jet and 50-60 kt low-level
   jet will result in a very favorable environment for organized
   convection, including the potential for long-track supercells and a
   corresponding strong tornado risk. Very strong low/midlevel flow
   fields will also support widespread damaging wind potential. 

   Some uncertainty remains regarding the northward extent of the most
   significant severe potential, given the presence of widespread
   convection in advance of the ejecting shortwave. Guidance also
   continues to trend slightly slower, with the GFS still a notably
   fast outlier. A 30% probability contour has been introduced from LA
   into central/southern MS/AL and southwest GA, where confidence is
   highest in the outbreak potential at this time.

   An organized severe thunderstorm threat will likely continue into
   Monday morning, with the potential for damaging wind and/or a few
   tornadoes likely spreading into portions of the Carolinas by 12Z
   Monday. 

May 20, 2019 which turned into a 45% tornado probability bust because *one thing* didn't verify... that being warm sector convection.

	

   ZCZC SPCSWOD48 ALL
   ACUS48 KWNS 170900
   SPC AC 170900

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0400 AM CDT Fri May 17 2019

   Valid 201200Z - 251200Z

   ...DISCUSSION...
   On D4/Monday, a lead shortwave trough will eject out of the base of
   the deep upper troughing over the western CONUS into the
   central/southern Plains. This lead wave is not expected to be
   particularly deep, with the more significant, deeper shortwave
   lagging back over the Southwest. This leads to the unique situation
   where strong moisture advection and backed surface winds are able to
   persist as a source of lift interacts with the warm sector. Wind
   fields are also impressively strong, with southwesterly 500 mb flow
   approaching 80 kt atop 50 kt 850 mb southerly flow and 20-25 kt
   southeasterly surface winds. The overall result of these factors is
   an environment strongly supportive of severe storms. An initial
   discrete mode capable of all severe hazards, including tornadoes, is
   anticipated. If a discrete mode can be maintained, strong tornadoes
   could occur. Upscale growth is eventually expected, with a strong
   MCS then tracking eastward across OK and adjacent portions of
   southern KS and north TX.

   The evolution of the MCS anticipated on D4/Monday will have a large
   impact on the downstream air mass and resulting severe threat on
   D5/Tuesday. Even so, current guidance shows good consensus that a
   shortwave and accompanying strong flow aloft will interact with a
   warm sector from roughly the MO river valley into the Mid-South.
   Uncertainty regarding cloud cover and resulting effective on diurnal
   heating and the extent of air mass destabilization currently
   preclude enough confidence to introduce a 30% outlook area.

 

Still amazing how the May 20, 2019 busted and a week later the OV event turned into a bigger tornado outbreak than anyone expected.

[Iceresistance]

1 hour ago, ClicheVortex2014 said:

Hodograph porn, anyone?

 

My goodness, it's a contaminated sounding though, but still.

[ClicheVortex2014]

Pivotalweather now has sbcape overlapped with hodographs. Amazing.

Warm sector is disgustingly ripe with sufficient instability and textbook hodographs for long-lived, tornadic supercells

 

Edited March 19, 2022 by ClicheVortex2014

[ClicheVortex2014]

2 hours ago, ClicheVortex2014 said:

Ok so I'm going to share some day 4 outlooks for previous significant events... keep in mind I'm not saying this event is comparable to any of the events because everything has to happen just right... and they did.

These all turned out to be high risks except for Easter 2020 which easily could've been. They all happen to be high-end events because those are the most memorable... I'm sure there are plenty of examples of events that had very strongly worded day 4 outlooks that turned out to be less threatening.

2011 Super Outbreak

DAY 4-8 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0350 AM CDT SUN APR 24 2011
   
   VALID 271200Z - 021200Z
   
   ...DISCUSSION...
   WIDESPREAD CONVECTIVE/SEVERE WEATHER EVENT -- ONGOING FROM THE DAY 3
   /TUE. 4-26/ PERIOD -- IS LIKELY TO CONTINUE SPREADING EWD ACROSS THE
   OH/TN VALLEYS AND GULF COAST STATES DAY 4 /WED. 4-27/...AS
   MEDIUM-RANGE MODELS BOTH FORECAST EWD PROGRESSION OF THE LARGE
   CENTRAL U.S. TROUGH.  AS THE COLD FRONT SHIFTS EWD TOWARD THE
   APPALACHIANS THROUGH THE AFTERNOON AND EVENING...PRE-FRONTAL WARM
   SECTOR FEATURING MODERATE INSTABILITY AND STRONG DEEP-LAYER SHEAR
   WILL SUPPORT CONTINUATION/REDEVELOPMENT OF SEVERE STORMS INTO THE
   AFTERNOON AND EVENING.  POTENTIAL FOR SUBSTANTIAL SEVERE WEATHER --
   INCLUDING HAIL/WIND AND ISOLATED TORNADOES -- SUPPORTS CONTINUATION
   OF A LARGE SEVERE WEATHER THREAT AREA FOR DAY 4.  

11/17/13

  DAY 4-8 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0400 AM CST THU NOV 14 2013

   VALID 171200Z - 221200Z

   ...DISCUSSION...
   SOME UNCERTAINTY LINGERS...BUT TRENDS IN THE MEDIUM RANGE FORECAST
   GUIDANCE ARE INCREASINGLY SUGGESTIVE OF THE DEVELOPMENT OF AN
   ENVIRONMENT SUPPORTIVE OF AN OUTBREAK OF SEVERE THUNDERSTORMS ACROSS
   PARTS OF THE MIDDLE MISSISSIPPI VALLEY EASTWARD THROUGH MUCH OF THE
   OHIO VALLEY ON SUNDAY.  MOST GUIDANCE NOW APPEARS GENERALLY FASTER
   WITH THE CONTINUED EASTWARD PROGRESSION OF A STRONG SHORT WAVE
   TROUGH...FROM THE CENTRAL PLAINS EARLY SUNDAY TO THE LOWER GREAT
   LAKES/UPPER OHIO VALLEY/CENTRAL APPALACHIANS REGION BY LATE SUNDAY
   NIGHT.  MOST MODELS ARE NOW SUGGESTIVE THAT THIS WILL BE ACCOMPANIED
   BY STRONG SURFACE CYCLOGENESIS...WITH MOST RAPID SURFACE PRESSURE
   FALLS ACROSS PARTS OF THE GREAT LAKES REGION AND OHIO VALLEY LATE
   SUNDAY AFTERNOON INTO SUNDAY NIGHT.  

   A 90+ KT 500 MB JET STREAK NOSING THROUGH THE OHIO VALLEY...COUPLED
   WITH STRENGTHENING SOUTHERLY WARM SECTOR 850 MB FLOW...PERHAPS IN
   EXCESS OF 70 KTS ACROSS PARTS OF THE OHIO VALLEY INTO THE LOWER
   GREAT LAKES...WILL CONTRIBUTE TO VERY STRONG DEEP LAYER WIND FIELDS
   AND SHEAR.  IT ALSO APPEARS INCREASINGLY PROBABLE THAT THIS WILL
   COINCIDE WITH AN INFLUX OF SEASONABLY HIGH MOISTURE CONTENT AT LEAST
   AS FAR NORTH AND EAST AS THE LOWER OHIO VALLEY...CONTRIBUTING TO
   SUFFICIENT CAPE FOR VIGOROUS STORM DEVELOPMENT.  SUPERCELLS WITH A
   RISK FOR TORNADOES WILL BE POSSIBLE...PARTICULARLY IN EARLY STAGES
   OF CONVECTIVE DEVELOPMENT...PERHAPS AS EARLY AS MID DAY ACROSS PARTS
   OF THE MIDDLE MISSISSIPPI INTO LOWER OHIO VALLEY VALLEY.

Easter 2020

 ...D4/Sunday: TX Gulf Coast eastward through the Southeast into the
   Carolinas...
   Ingredients for a potential severe thunderstorm outbreak appear
   likely to come together Sunday into Sunday night. An ejecting
   shortwave trough is forecast to take on a neutral to somewhat
   negative tilt by Sunday afternoon as it moves quickly
   east-northeastward across the Southeast states. Rich low-level
   moisture will be drawn inland from the Gulf of Mexico in advance of
   a deepening surface low that will move from the mid-MS Valley into
   the Ohio Valley by Monday morning. Moderate destabilization in
   conjunction with an 80-100 kt midlevel jet and 50-60 kt low-level
   jet will result in a very favorable environment for organized
   convection, including the potential for long-track supercells and a
   corresponding strong tornado risk. Very strong low/midlevel flow
   fields will also support widespread damaging wind potential. 

   Some uncertainty remains regarding the northward extent of the most
   significant severe potential, given the presence of widespread
   convection in advance of the ejecting shortwave. Guidance also
   continues to trend slightly slower, with the GFS still a notably
   fast outlier. A 30% probability contour has been introduced from LA
   into central/southern MS/AL and southwest GA, where confidence is
   highest in the outbreak potential at this time.

   An organized severe thunderstorm threat will likely continue into
   Monday morning, with the potential for damaging wind and/or a few
   tornadoes likely spreading into portions of the Carolinas by 12Z
   Monday. 

May 20, 2019 which turned into a 45% tornado probability bust because *one thing* didn't verify... that being warm sector convection.

	

   ZCZC SPCSWOD48 ALL
   ACUS48 KWNS 170900
   SPC AC 170900

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0400 AM CDT Fri May 17 2019

   Valid 201200Z - 251200Z

   ...DISCUSSION...
   On D4/Monday, a lead shortwave trough will eject out of the base of
   the deep upper troughing over the western CONUS into the
   central/southern Plains. This lead wave is not expected to be
   particularly deep, with the more significant, deeper shortwave
   lagging back over the Southwest. This leads to the unique situation
   where strong moisture advection and backed surface winds are able to
   persist as a source of lift interacts with the warm sector. Wind
   fields are also impressively strong, with southwesterly 500 mb flow
   approaching 80 kt atop 50 kt 850 mb southerly flow and 20-25 kt
   southeasterly surface winds. The overall result of these factors is
   an environment strongly supportive of severe storms. An initial
   discrete mode capable of all severe hazards, including tornadoes, is
   anticipated. If a discrete mode can be maintained, strong tornadoes
   could occur. Upscale growth is eventually expected, with a strong
   MCS then tracking eastward across OK and adjacent portions of
   southern KS and north TX.

   The evolution of the MCS anticipated on D4/Monday will have a large
   impact on the downstream air mass and resulting severe threat on
   D5/Tuesday. Even so, current guidance shows good consensus that a
   shortwave and accompanying strong flow aloft will interact with a
   warm sector from roughly the MO river valley into the Mid-South.
   Uncertainty regarding cloud cover and resulting effective on diurnal
   heating and the extent of air mass destabilization currently
   preclude enough confidence to introduce a 30% outlook area.

 

 

Forgot about late April 2014.

Day 4 for April 27, 2014... high risk for Arkansas. High-end EF4 verified (Mayflower-Vilonia). Also turned out to be a day 3 moderate risk, like 4/27/11 and 5/20/19 was. 

  DAY 4-8 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0338 AM CDT THU APR 24 2014

   VALID 271200Z - 021200Z

   ...DISCUSSION...
   ...SIGNIFICANT MULTI-DAY SEVERE EVENT EXPECTED ACROSS PORTIONS OF
   THE CENTRAL/SOUTHERN PLAINS AND MS VALLEY SUNDAY...AND MS
   VALLEY/CNTRL GULF STATES ON MONDAY...STRONG TORNADOES ARE
   POSSIBLE...

   BOTH THE ECMWF/GFS ARE IN GENERAL AGREEMENT REGARDING THE EVOLUTION
   OF UPPER LOW AS IT PROGRESSES INTO THE PLAINS SUNDAY...THEN INTO THE
   MS VALLEY MONDAY.  AFTER INITIAL SPEED MAX EJECTS INTO THE CNTRL
   PLAINS SUNDAY SUBSTANTIAL MID-LEVEL FLOW DEVELOPS WITHIN THE BASE OF
   THE TROUGH OVER TX AND SPREADS ACROSS THE LOWER MS VALLEY INTO THE
   NCNTRL GULF STATES/TN VALLEY.  ECMWF IS MORE SUPPRESSED WITH THIS
   STRONGER FLOW THAN THE GFS BUT THE IDEA THAT STRONG FLOW SHOULD
   OVERSPREAD A BUOYANT AIRMASS BOTH DAYS REMAINS.

   MODELS CONTINUE TO SURGE THE DRYLINE ACROSS THE PLAINS EARLY IN THE
   PERIOD WITH BOTH AGREEING THAT SIGNIFICANT BOUNDARY LAYER DRYING
   WILL SPREAD EAST OF I-35 CORRIDOR FAIRLY EARLY SUNDAY.  GIVEN THE
   MID-LEVEL JET THAT EJECTS INTO THE CNTRL PLAINS EARLY THIS MAY
   TRANSPIRE AND SEVERE THUNDERSTORMS SHOULD EVOLVE FROM SERN
   NEB...ACROSS ERN KS/OK INTO NERN TX BEFORE SPREADING INTO WRN
   MO/AR/NWRN LA.

Day 4 outlook for 4/28/14. Turned out to be another day 3 moderate risk, day 1 high risk.

   DAY 4-8 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0351 AM CDT FRI APR 25 2014

   VALID 281200Z - 031200Z

   ...DISCUSSION...
   ...MULTI-DAY SEVERE EPISODE SHOULD CONTINUE INTO AT LEAST TUESDAY
   FROM THE OH VALLEY TO THE CNTRL GULF COAST. POTENTIAL EXISTS FOR A
   SEVERE WEATHER OUTBREAK INCLUDING STRONG TORNADOES...

   ACTIVE SEVERE WEATHER PATTERN WILL PERSIST WITH A BROAD UPPER-LEVEL
   TROUGH CENTERED OVER THE CNTRL CONUS. ECMWF/GFS/UKMET/CMC ARE RATHER
   CONSISTENT WITH THE EVOLUTION OF INTENSE MID-LEVEL SPEED MAXIMA
   ROTATING THROUGH THE BASE OF THE TROUGH INTO D5/TUE. THESE WINDS
   WILL OVERSPREAD PARTS OF A BROAD WARM/MOIST SECTOR CHARACTERIZED BY
   60S SURFACE DEW POINTS. DESPITE MULTIPLE DAYS OF EXTENSIVE WARM
   SECTOR CONVECTION...DIURNAL HEATING COUPLED WITH W/SWLYS IN THE
   MID-LEVELS SHOULD RECHARGE/STEEPEN LAPSE RATES...POTENTIALLY
   YIELDING MODERATE TO STRONG INSTABILITY EACH AFTERNOON. OF THE TWO
   DAYS HIGHLIGHTED...D5/TUE APPEARS TO HAVE SLIGHTLY GREATER OUTBREAK
   POTENTIAL WITH A 90+ KT 500-MB JET EJECTING OUT OF THE BASE OF THE
   TROUGH.

 

Edited March 19, 2022 by ClicheVortex2014

[Central Illinois]

I could easily see them going moderate in the next outlook

[ClicheVortex2014]

JAN, the heart of the day 4 enhanced risk, echos some of the same things as SPC but they put emphasis on storm mode. 

Surface cyclogenesis will occur on Monday over the Texas panhandle
with the low deepening to ~995mb beneath strong upper divergence as
it shifts northeast into Missouri by Tuesday. Intense convection
will initiate upstream across east Texas on Monday ahead of an
advancing dryline and will move into the ArkLaTex overnight. Some of
this activity may encroach on the western edge of the CWA early
Tuesday morning and could bring an early round of severe weather
mainly west of the Mississippi River. This activity is expected to
lift north Tuesday morning on the leading edge of rapid moisture
return as dewpoints surge into the mid to upper 60s with low 70s
possible. This will set the stage for the main round of potentially
significant severe weather during the day and into the evening
hours. The lead shortwave trough embedded within the mean longwave
will take on a negative tilt as it lifts across the Lower
Mississippi Valley. Subsequent height falls will overspread the
region and will provide adequate forcing for ascent in concert with
continued strong upper divergence. Intense convection is expected to
initiate across central Louisiana during the mid to late morning
hours and push east across the area through the day and into the
early evening within a pre-frontal surface trough.

Convection will reside within high-end parameter space as rich
boundary layer moisture and cool air aloft will yield moderately
steep lapse rates and 1000-1500 J/kg of MLCAPE. In addition, robust
wind fields will be supportive of 35-45kts of 0-1km vertical wind
shear and 300-500 m2/s2 of 0-1km SRH. As such, all modes of severe
weather will be possible with the potential for tornadoes, damaging
winds and large hail. The synoptic pattern as well as the
aforementioned environment are indicative of a potentially
significant severe weather episode, however, lingering uncertainty
is focused around storm mode and convective evolution. These details
are not yet apparent at this time range, but early indications are
for a mixed mode of QLCS along with supercells followed by eventual
upscale growth into a predominately linear storm mode with embedded
supercell structures. Even with a linear storm mode, the environment
would still support an intense line of storms with damaging winds
and tornadoes. In addition to severe weather, a period of training
convection overnight Monday into Tuesday morning across the Delta
may result in flash flooding. A swath of 3-5" of rainfall may be
realized, but exact placement remains uncertain. Will hold off on
mention in the HWO/graphics for now until placement can be nailed
down.

 

Both of the following days had extremely high-end parameters and discrete warm sector convection was expected. The parameters verified in both cases but the warm sector activity... didn't. 

 

HRRR was showing an unbelievable outbreak just 12 hours out on the morning of 5/20/19. So storm mode really is a believe-it-when-I-see-it thing... though I'm more inclined to believe warm sector/pre-squall convection in Dixie Alley than Oklahoma because they have a stronger history of that. Has to do with weaker caps and such.

 

Edited March 19, 2022 by ClicheVortex2014

[ClicheVortex2014]

 

[Ingyball]

All in all, looks like it will be a good rain event here in Kansas. 1-2" will go along way towards erasing the drought here, doesn't take as much as some places further south. Helps that central portions of the state saw 0.5-1" last week. If we can keep a somewhat active pattern going into April, I'm feeling more confident about the peak of Central and Northern Plains severe season. 

[Iceresistance]

21z SREF already has a 75% Contour over Louisiana

[ClicheVortex2014]

First look at HRRR for Monday. The model is unreliable at this range but it's always interesting.

 

[ClicheVortex2014]

ARW and NSSL get going around 7pm local time on Monday. Cliffhanger. Unfortunately this might be a late evening/early overnight event.

I'm not sure about whether SPC will go with a day 2 moderate... I think a day 3 moderate is more likely, ironically. Tuesday has moderate risk potential due to the squall and extreme wind shear alone... albeit for damaging winds. Monday will have to be tornado threat-driven. 

I'd go with 10% hatched for tornadoes for day 2, and if they broke the day 3 probabilities into categories, I'd do the same for day 3. Too early to be that certain about discrete/warm sector convection. We should have a slightly better picture for Monday by the second day 2 update.

 

 

Edited March 20, 2022 by ClicheVortex2014

[ElectricStorm]

I think it's a tossup between moderate and enhanced for the initial Day 2 outlook, leaning towards enhanced. Probably will be moderate at some point though. 

I think the Day 3 is also a tossup. Really could go either way here but since Day 3 moderates are so rare, I'm guessing they might keep it at enhanced for now. 

[Ingyball]

Not quite trusting the NAM right now. It did horrible with Thursday's storm here. There were a couple of runs that gave us nothing lol. Seems like it's trying to do that again where it's too far south and east with everything.

[Chinook]

For those interested, the Midnight Day-2 outlook has... enhanced with 10% hatched tornado risk and some areas of 30% hatched hail risk closer to Austin, no hatched by Houston. Same type of areas for enhanced type outlook. I won't post the whole discussion, as it is midnight and I don't feel like reading it.