Enhanced for Day 3 SPC (Saturday 12-28-2024)
PC AC 261933
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0133 PM CST Thu Dec 26 2024
Valid 281200Z - 291200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTH-CENTRAL LOUISIANA ACROSS MUCH OF CENTRAL MISSISSIPPI AND INTO FAR WEST-CENTRAL ALABAMA....
...SUMMARY... Severe storms are expected Saturday from north-central Louisiana to west-central Alabama on Saturday. All severe weather hazards are possible.
...Synopsis... A mid-level trough centered across the Texas Panhandle will move quickly across the southern Plains and become negatively tilted across the Ozarks by Saturday evening and into the Ohio Valley by Sunday morning. Rich low-level moisture will start to move inland across the Gulf Coast by 12Z Saturday and continue to advance inland through the day as low-level flow strengthens across the warm sector ahead of the surface low.
...Lower/Mid Mississippi Valley across the Southeast... A broad warm sector will be advancing inland across the Gulf Coast states Saturday morning as low-level flow strengthens ahead of the approaching trough. Initially, the warm sector will likely be mostly uncontaminated, but thunderstorm activity is expected to increase through the morning as the low-level jet strengthens. The timing and location of this morning convection will have a significant impact on the location and intensity of the severe weather threat on Saturday. Variance amongst forecast guidance unsurprisingly remains high given the very progressive mid-level pattern. Despite the uncertainty on specifics, a broad warm sector with mid 60s dewpoints, a negatively tilted trough, and a strengthening low-level jet will support the potential for a severe weather outbreak with multiple rounds of storms with all severe weather hazards possible. Given the timing/amplitude differences with the mid-level pattern, the highest threat corridor will likely shift in future outlooks. The GEFS is slightly slower than the operational GFS with the EPS slightly faster than the ECMWF suggesting a most likely solution somewhere in between.
Within the enhanced risk corridor, forecast soundings show 45 to 50 knots of effective shear and instability ranging from 1000 to 2000 J/kg MLCAPE. This will support supercells with all severe weather hazards across much of the warm sector from northern Louisiana to western Alabama as early as late morning. The tornado threat remains more uncertain based on the final evolution of the mid-level trough. A slower trough ejection (such as is shown by the ECMWF) may cause more issues with destabilization and less favorable low-level hodographs as the low-level jet ramp up is delayed.
The severe weather threat is expected to continue after dark from central Mississippi into western Alabama. Somewhere near central Alabama the convective intensity will likely start to wane as the mid-level trough starts to pull away and heights start to rise across the warm sector.
PC AC 261933
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0133 PM CST Thu Dec 26 2024
Valid 281200Z - 291200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTH-CENTRAL LOUISIANA ACROSS MUCH OF CENTRAL MISSISSIPPI AND INTO FAR WEST-CENTRAL ALABAMA....
...SUMMARY... Severe storms are expected Saturday from north-central Louisiana to west-central Alabama on Saturday. All severe weather hazards are possible.
...Synopsis... A mid-level trough centered across the Texas Panhandle will move quickly across the southern Plains and become negatively tilted across the Ozarks by Saturday evening and into the Ohio Valley by Sunday morning. Rich low-level moisture will start to move inland across the Gulf Coast by 12Z Saturday and continue to advance inland through the day as low-level flow strengthens across the warm sector ahead of the surface low.
...Lower/Mid Mississippi Valley across the Southeast... A broad warm sector will be advancing inland across the Gulf Coast states Saturday morning as low-level flow strengthens ahead of the approaching trough. Initially, the warm sector will likely be mostly uncontaminated, but thunderstorm activity is expected to increase through the morning as the low-level jet strengthens. The timing and location of this morning convection will have a significant impact on the location and intensity of the severe weather threat on Saturday. Variance amongst forecast guidance unsurprisingly remains high given the very progressive mid-level pattern. Despite the uncertainty on specifics, a broad warm sector with mid 60s dewpoints, a negatively tilted trough, and a strengthening low-level jet will support the potential for a severe weather outbreak with multiple rounds of storms with all severe weather hazards possible. Given the timing/amplitude differences with the mid-level pattern, the highest threat corridor will likely shift in future outlooks. The GEFS is slightly slower than the operational GFS with the EPS slightly faster than the ECMWF suggesting a most likely solution somewhere in between.
Within the enhanced risk corridor, forecast soundings show 45 to 50 knots of effective shear and instability ranging from 1000 to 2000 J/kg MLCAPE. This will support supercells with all severe weather hazards across much of the warm sector from northern Louisiana to western Alabama as early as late morning. The tornado threat remains more uncertain based on the final evolution of the mid-level trough. A slower trough ejection (such as is shown by the ECMWF) may cause more issues with destabilization and less favorable low-level hodographs as the low-level jet ramp up is delayed.
The severe weather threat is expected to continue after dark from central Mississippi into western Alabama. Somewhere near central Alabama the convective intensity will likely start to wane as the mid-level trough starts to pull away and heights start to rise across the warm sector.