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Severe Weather Threat 4/27-4/28

Hot off the presses:

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1150 AM CDT MON APR 27 2026

VALID 271630Z - 281200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS
EAST/SOUTHEAST MISSOURI...SOUTHERN ILLINOIS...WESTERN KENTUCKY...AND
NORTHWEST TENNESSEE...

..SUMMARY

NUMEROUS SEVERE THUNDERSTORMS ARE EXPECTED FROM THE MID
MISSISSIPPI/LOWER OHIO VALLEYS INTO THE MID-SOUTH THROUGH THIS
EVENING, WITH A THREAT FOR MULTIPLE STRONG TO INTENSE TORNADOES
(EF3+), WIDESPREAD SEVERE/DAMAGING WIND GUSTS, AND SCATTERED LARGE
TO VERY LARGE HAIL.

...MID MISSISSIPPI VALLEY/MIDWEST INTO THE MID-SOUTH/LOWER
MISSISSIPPI VALLEY...
FORECAST SCENARIO LARGELY UNCHANGED IN THAT A VERY ACTIVE
SEVERE-WEATHER/TORNADO DAY IS EXPECTED REGIONALLY, ESPECIALLY INTO
LATE AFTERNOON AND THIS EVENING. INITIALLY, A RELATIVELY LONG-LIVED
LINEAR CLUSTER OF CONVECTION PERSISTS AT LATE MORNING ACROSS
EAST-CENTRAL/SOUTH-CENTRAL ILLINOIS, WITH ADDITIONAL INITIALLY
ELEVATED STORMS ON ITS EASTERN/SOUTHERN PERIPHERY, MOVING FROM
EASTERN ILLINOIS INTO INDIANA, WITH SEVERE HAIL AND DAMAGING WINDS
PERSISTING AS EARLY DAY HAZARDS.

OVER TIME, AIR MASS WILL CONTINUE TO MOISTEN AND RAPIDLY DESTABILIZE
ALONG/SOUTH OF THE MCS-ASSOCIATED OUTFLOW FROM CENTRAL MISSOURI INTO
SOUTH-CENTRAL ILLINOIS. A MID/UPPER-LEVEL TROUGH WILL EJECT
NORTHEASTWARD FROM THE NORTHERN/CENTRAL PLAINS INTO THE MIDWEST AND
MIDDLE MISSISSIPPI VALLEY THROUGH THE PERIOD. LOW-LEVEL MASS
RESPONSE WILL ENCOURAGE THE PRIMARY SURFACE LOW TO CONSOLIDATE
ACROSS MINNESOTA/WISCONSIN BY THIS EVENING, WITH A WARM FRONT
EFFECTIVELY DELINEATED BY THE MORNING CONVECTION.

STRENGTHENING WEST-SOUTHWESTERLY FLOW ALOFT ASSOCIATED WITH A 50-70
KT MID-LEVEL JET WILL OVERSPREAD MUCH OF THE WARM SECTOR BY PEAK
HEATING, AND A 35-45 KT SOUTH-SOUTHWESTERLY LOW-LEVEL JET WILL BOTH
PROVIDE AMPLE LOW-LEVEL AND DEEP-LAYER SHEAR TO SUPPORT SUPERCELLS.
INITIALLY DISCRETE SURFACE-BASED DEVELOPMENT APPEARS LIKELY TO OCCUR
INTO MID-AFTERNOON ACROSS THE MID MISSISSIPPI VALLEY/MID-SOUTH AHEAD
OF THE SURFACE COLD FRONT, AND PERHAPS ALONG WEAK LOW-LEVEL
CONFLUENCE ZONES IN THE OPEN WARM SECTOR INCLUDING GENERALLY NEAR
THE CONFLUENCE OF THE MISSISSIPPI/OHIO RIVERS SOUTHWARD INTO THE
MID-SOUTH.

THESE SUPERCELLS WILL EXIST IN A VERY FAVORABLE ENVIRONMENT FOR
TORNADOES THROUGH THE AFTERNOON AND EVENING, AND MULTIPLE STRONG TO
INTENSE TORNADOES (EF2/3+) APPEAR LIKELY, ESPECIALLY FROM PARTS OF
MISSOURI INTO ILLINOIS ALONG/NEAR THE EFFECTIVE FRONT. THIS STRONG
TORNADO POTENTIAL WILL ALSO LIKELY EXTEND FARTHER SOUTH WITHIN THE
WARM SECTOR INTO THE MID-SOUTH.

BY EARLY EVENING, CONVECTION WILL PROBABLY TEND TO CONSOLIDATE INTO
CLUSTERS OF SUPERCELLS AND THEN MORE LINEAR SEGMENTS WITH SOME
INCREASE IN DAMAGING WIND POTENTIAL ASIDE FROM LARGE HAIL AND A
CONTINUED MULTI-MODE TORNADO RISK TONIGHT.

..ARKLATEX INTO TEXAS

WHILE STORM COVERAGE MAY TREND LESSER WITH SOUTHWEST EXTENT, THE
POTENTIAL FOR AT LEAST ISOLATED INTENSE STORMS WILL EXIST ACROSS THE
REGION. SUPERCELLS CAPABLE OF PRODUCING LARGE TO VERY LARGE HAIL AND
OCCASIONAL DAMAGING WINDS ARE EXPECTED. INCREASING LOW-LEVEL
WARM/MOIST ADVECTION TONIGHT COULD FOSTER ADDITIONAL ROBUST
THUNDERSTORMS ALONG THE RETREATING DRYLINE AND EVENTUALLY THE
SOUTHWARD-MOVING COLD FRONT.

..GUYER/WEINMAN.. 04/27/2026
Click to expand...
 
Outlook's out. 20 mins late. Kept moderate (obviously).
769
ACUS01 KWNS 271651
SWODY1
SPC AC 271650

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1150 AM CDT MON APR 27 2026

VALID 271630Z - 281200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS
EAST/SOUTHEAST MISSOURI...SOUTHERN ILLINOIS...WESTERN KENTUCKY...AND
NORTHWEST TENNESSEE...

..SUMMARY

NUMEROUS SEVERE THUNDERSTORMS ARE EXPECTED FROM THE MID
MISSISSIPPI/LOWER OHIO VALLEYS INTO THE MID-SOUTH THROUGH THIS
EVENING, WITH A THREAT FOR MULTIPLE STRONG TO INTENSE TORNADOES
(EF3+), WIDESPREAD SEVERE/DAMAGING WIND GUSTS, AND SCATTERED LARGE
TO VERY LARGE HAIL.

...MID MISSISSIPPI VALLEY/MIDWEST INTO THE MID-SOUTH/LOWER
MISSISSIPPI VALLEY...
FORECAST SCENARIO LARGELY UNCHANGED IN THAT A VERY ACTIVE
SEVERE-WEATHER/TORNADO DAY IS EXPECTED REGIONALLY, ESPECIALLY INTO
LATE AFTERNOON AND THIS EVENING. INITIALLY, A RELATIVELY LONG-LIVED
LINEAR CLUSTER OF CONVECTION PERSISTS AT LATE MORNING ACROSS
EAST-CENTRAL/SOUTH-CENTRAL ILLINOIS, WITH ADDITIONAL INITIALLY
ELEVATED STORMS ON ITS EASTERN/SOUTHERN PERIPHERY, MOVING FROM
EASTERN ILLINOIS INTO INDIANA, WITH SEVERE HAIL AND DAMAGING WINDS
PERSISTING AS EARLY DAY HAZARDS.

OVER TIME, AIR MASS WILL CONTINUE TO MOISTEN AND RAPIDLY DESTABILIZE
ALONG/SOUTH OF THE MCS-ASSOCIATED OUTFLOW FROM CENTRAL MISSOURI INTO
SOUTH-CENTRAL ILLINOIS. A MID/UPPER-LEVEL TROUGH WILL EJECT
NORTHEASTWARD FROM THE NORTHERN/CENTRAL PLAINS INTO THE MIDWEST AND
MIDDLE MISSISSIPPI VALLEY THROUGH THE PERIOD. LOW-LEVEL MASS
RESPONSE WILL ENCOURAGE THE PRIMARY SURFACE LOW TO CONSOLIDATE
ACROSS MINNESOTA/WISCONSIN BY THIS EVENING, WITH A WARM FRONT
EFFECTIVELY DELINEATED BY THE MORNING CONVECTION.

STRENGTHENING WEST-SOUTHWESTERLY FLOW ALOFT ASSOCIATED WITH A 50-70
KT MID-LEVEL JET WILL OVERSPREAD MUCH OF THE WARM SECTOR BY PEAK
HEATING, AND A 35-45 KT SOUTH-SOUTHWESTERLY LOW-LEVEL JET WILL BOTH
PROVIDE AMPLE LOW-LEVEL AND DEEP-LAYER SHEAR TO SUPPORT SUPERCELLS.
INITIALLY DISCRETE SURFACE-BASED DEVELOPMENT APPEARS LIKELY TO OCCUR
INTO MID-AFTERNOON ACROSS THE MID MISSISSIPPI VALLEY/MID-SOUTH AHEAD
OF THE SURFACE COLD FRONT, AND PERHAPS ALONG WEAK LOW-LEVEL
CONFLUENCE ZONES IN THE OPEN WARM SECTOR INCLUDING GENERALLY NEAR
THE CONFLUENCE OF THE MISSISSIPPI/OHIO RIVERS SOUTHWARD INTO THE
MID-SOUTH.

THESE SUPERCELLS WILL EXIST IN A VERY FAVORABLE ENVIRONMENT FOR
TORNADOES THROUGH THE AFTERNOON AND EVENING, AND MULTIPLE STRONG TO
INTENSE TORNADOES (EF2/3+) APPEAR LIKELY, ESPECIALLY FROM PARTS OF
MISSOURI INTO ILLINOIS ALONG/NEAR THE EFFECTIVE FRONT. THIS STRONG
TORNADO POTENTIAL WILL ALSO LIKELY EXTEND FARTHER SOUTH WITHIN THE
WARM SECTOR INTO THE MID-SOUTH.

BY EARLY EVENING, CONVECTION WILL PROBABLY TEND TO CONSOLIDATE INTO
CLUSTERS OF SUPERCELLS AND THEN MORE LINEAR SEGMENTS WITH SOME
INCREASE IN DAMAGING WIND POTENTIAL ASIDE FROM LARGE HAIL AND A
CONTINUED MULTI-MODE TORNADO RISK TONIGHT.

..ARKLATEX INTO TEXAS

WHILE STORM COVERAGE MAY TREND LESSER WITH SOUTHWEST EXTENT, THE
POTENTIAL FOR AT LEAST ISOLATED INTENSE STORMS WILL EXIST ACROSS THE
REGION. SUPERCELLS CAPABLE OF PRODUCING LARGE TO VERY LARGE HAIL AND
OCCASIONAL DAMAGING WINDS ARE EXPECTED. INCREASING LOW-LEVEL
WARM/MOIST ADVECTION TONIGHT COULD FOSTER ADDITIONAL ROBUST
THUNDERSTORMS ALONG THE RETREATING DRYLINE AND EVENTUALLY THE
SOUTHWARD-MOVING COLD FRONT.

..GUYER/WEINMAN.. 04/27/2026
Click to expand...
 
Today is probably the most complex severe weather setup we have had in a while - dare I say all year - which is troublesome when we are trying to differentiate between
what could be a high-end tornado outbreak and your more ordinary April event.

First things first, the overall synoptic is impressive with a large trough pushing through the Central US. Estimates on the translation speed vary but I would say are mostly above 40kts, the now well-known Chris Broyles' Omega value. The speed/vorticity maximum also appears to dig directly E after 00z (as opposed to moving off to the NE) which helps from a forcing point of view, and means the strong upper level flow is directly above the warm sector.

The second thing to note is that the tornado threat will be starting a bit earlier and further East than some may expect. Models suggest the axis of the current LLJ segment will be positioned from C IL down the Mississippi river. I think that the combination of WAA storms along what could be subtle confluence is likely to lead to the development of storms as early as 21/22z in a corridor from N MS (through W TN/KY, perhaps E AR) into S IL. The environment here will not be as favourable as areas further West, but HREF suggests still STP 2-4. As such I could see a couple tornadic supercells, with the risk for strong tornadoes (In terms of SPC outlooks this in my mind would be more in line with a CIG1 distribution).

In terms of the main MDT risk area - this is where major uncertainties lie. We have seen the current MCS continue to move East, leaving a remnant OFB which is oriented E-W across MO. This is now being modified North by the very strong low level flow and moisture advection. Even as the trailing thunderstorms decay, it seems very likely this boundary will be the focus for convective initiation. The environment along and just south of this boundary will be very potent, and a robust supercell would certainly have an intense tornado risk. That being said, given the orientation, it will be extremely easy for storms to grow upscale into clusters quickly, and any surface based updrafts to get cut off by outflow. A higher end tornado threat will depend on storms being to initiate just ahead of the boundary (as a few earlier HRRR runs showed) or develop an orientation relative to the other storms that allows it to ingest surface based parcels.

Later on, CAMS develop more storms along what seems to be a sort of cold front type feature. This feature is also pretty flow parallel, so we will see similar issues with storms growing upscale. That being said, I think we could see embedded supercell structures from this, especially as it moves further East into stronger low level shear.

The highest end potential is if we were to see any discrete supercells develop fully in the high STP OWS from N AR into SE MO and SW IL. In this scenario, I think we are looking at EF3+ tornadoes. The saving grace is, currently, I can't quite see an easy forcing mechanism for this to occur, given the confluence would probably be displaced East, the boundaries growing upscale, and the strongest synoptic forcing a tad to the north. That's not to say it won't happen though.

Those are some of my thoughts for now. Its annoying I can't upload any photos to visualise these points, but they can all be seen easily on model output. I think Moderate Risk is definitely a good call from the SPC - I don't think there is much basis to go higher. While I do think a tornado outbreak is probably on the cards - given the synoptic, large area of favourable parameters and multiple storm modes, some of the key components of proper higher end outbreaks aren't yet apparent to me personally (if we really want to differentiate). Will be a dangerous weather day regardless though, so worth keeping an eye on all radar and warnings closely.
 
UK_EF4 said:
Today is probably the most complex severe weather setup we have had in a while - dare I say all year - which is troublesome when we are trying to differentiate between
what could be a high-end tornado outbreak and your more ordinary April event.

First things first, the overall synoptic is impressive with a large trough pushing through the Central US. Estimates on the translation speed vary but I would say are mostly above 40kts, the now well-known Chris Broyles' Omega value. The speed/vorticity maximum also appears to dig directly E after 00z (as opposed to moving off to the NE) which helps from a forcing point of view, and means the strong upper level flow is directly above the warm sector.

The second thing to note is that the tornado threat will be starting a bit earlier and further East than some may expect. Models suggest the axis of the current LLJ segment will be positioned from C IL down the Mississippi river. I think that the combination of WAA storms along what could be subtle confluence is likely to lead to the development of storms as early as 21/22z in a corridor from N MS (through W TN/KY, perhaps E AR) into S IL. The environment here will not be as favourable as areas further West, but HREF suggests still STP 2-4. As such I could see a couple tornadic supercells, with the risk for strong tornadoes (In terms of SPC outlooks this in my mind would be more line line with a CIG1 distribution).

In terms of the main MDT risk area - this is where major uncertainties lie. We have seen the current MCS continue to move East, leaving a remnant OFB which is oriented E-W across MO. This is now being modified North by the very strong low level flow and moisture advection. Even as the trailing thunderstorms decay, it seems very likely this boundary will be the focus for convective initiation. The environment along and just south of this boundary will be very potent, and a robust supercell would certainly have an intense tornado risk. That being said, given the orientation, it will be extremely easy for storms to grow upscale into clusters quickly, and any surface based updrafts to get cut off by outflow. A higher end tornado threat will depend on storms being to initiate just ahead of the boundary (as a few earlier HRRR runs showed) or develop an orientation relative to the other storms that allows it to ingest surface based parcels.

Later on, CAMS develop more storms along what seems to be a sort of cold front type feature. This feature is also pretty flow parallel, so we will see similar issues with storms growing upscale. That being said, I think we could see embedded supercell structures from this, especially as it moves further East into stronger low level shear.

The highest end potential is if we were to see any discrete supercells develop fully in the high STP OWS from N AR into SE MO and SW IL. In this scenario, I think we are looking at EF3+ tornadoes. The saving grace is, currently, I can't quite see an easy forcing mechanism for this to occur, given the confluence would probably be displaced East, the boundaries growing upscale, and the strongest synoptic forcing a tad to the north. That's not to say it won't happen though.

Those are some of my thoughts for now. Its annoying I can't upload any photos to visualise these points, but they can all be seen easily on model output. I think Moderate Risk is definitely a good call from the SPC - I don't think there is much basis to go higher. While I do think a tornado outbreak is probably on the cards - given the synoptic, large area of favourable parameters and multiple storm modes, some of the key components of proper higher end outbreaks aren't yet apparent to me personally (if we really want to differentiate). Will be a dangerous weather day regardless though, so worth keeping an eye on all radar and warnings closely.
Click to expand...
There he is!! Yes yes!
 
UK_EF4 said:
Today is probably the most complex severe weather setup we have had in a while - dare I say all year - which is troublesome when we are trying to differentiate between
what could be a high-end tornado outbreak and your more ordinary April event.

First things first, the overall synoptic is impressive with a large trough pushing through the Central US. Estimates on the translation speed vary but I would say are mostly above 40kts, the now well-known Chris Broyles' Omega value. The speed/vorticity maximum also appears to dig directly E after 00z (as opposed to moving off to the NE) which helps from a forcing point of view, and means the strong upper level flow is directly above the warm sector.

The second thing to note is that the tornado threat will be starting a bit earlier and further East than some may expect. Models suggest the axis of the current LLJ segment will be positioned from C IL down the Mississippi river. I think that the combination of WAA storms along what could be subtle confluence is likely to lead to the development of storms as early as 21/22z in a corridor from N MS (through W TN/KY, perhaps E AR) into S IL. The environment here will not be as favourable as areas further West, but HREF suggests still STP 2-4. As such I could see a couple tornadic supercells, with the risk for strong tornadoes (In terms of SPC outlooks this in my mind would be more in line with a CIG1 distribution).

In terms of the main MDT risk area - this is where major uncertainties lie. We have seen the current MCS continue to move East, leaving a remnant OFB which is oriented E-W across MO. This is now being modified North by the very strong low level flow and moisture advection. Even as the trailing thunderstorms decay, it seems very likely this boundary will be the focus for convective initiation. The environment along and just south of this boundary will be very potent, and a robust supercell would certainly have an intense tornado risk. That being said, given the orientation, it will be extremely easy for storms to grow upscale into clusters quickly, and any surface based updrafts to get cut off by outflow. A higher end tornado threat will depend on storms being to initiate just ahead of the boundary (as a few earlier HRRR runs showed) or develop an orientation relative to the other storms that allows it to ingest surface based parcels.

Later on, CAMS develop more storms along what seems to be a sort of cold front type feature. This feature is also pretty flow parallel, so we will see similar issues with storms growing upscale. That being said, I think we could see embedded supercell structures from this, especially as it moves further East into stronger low level shear.

The highest end potential is if we were to see any discrete supercells develop fully in the high STP OWS from N AR into SE MO and SW IL. In this scenario, I think we are looking at EF3+ tornadoes. The saving grace is, currently, I can't quite see an easy forcing mechanism for this to occur, given the confluence would probably be displaced East, the boundaries growing upscale, and the strongest synoptic forcing a tad to the north. That's not to say it won't happen though.

Those are some of my thoughts for now. Its annoying I can't upload any photos to visualise these points, but they can all be seen easily on model output. I think Moderate Risk is definitely a good call from the SPC - I don't think there is much basis to go higher. While I do think a tornado outbreak is probably on the cards - given the synoptic, large area of favourable parameters and multiple storm modes, some of the key components of proper higher end outbreaks aren't yet apparent to me personally (if we really want to differentiate). Will be a dangerous weather day regardless though, so worth keeping an eye on all radar and warnings closely.
Click to expand...
Stellar as it gets on here, man. I completely agree. Roll clouds are beginning to erode over S MO currently, but we still need more clearing to the SE for us to get going.
 
Ln
WeathermanLeprechaun said:
Stellar as it gets on here, man. I completely agree. Roll clouds are beginning to erode over S MO currently, but we still need more clearing to the SE for us to get going.
Click to expand...
Memphis area getting good sun breaks now. For a update here clouds rolling out fast
 
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