Day 4, 30% risk.
..SEVERE WEATHER OUTBREAK POSSIBLE ON D4/SAT...
...DISCUSSION... ...Day 4/Sat - Central Gulf Coast States to the Ohio Valley...
A strong large-scale upper trough is forecast to quickly move across the Plains to the MS Valley on Saturday. An intense jet streak will move across the Deep South into the OH Valley as this occurs. At the surface, a low secondary to the 980 mb low over the Upper Midwest is forecast to develop during the late morning/early afternoon across the mid-South. This will aid in further northward transport of rich Gulf moisture into portions of the Lower MS Valley and TN Valleys. Atop this moisture-primed boundary layer, cold 500 mb temperatures are forecast. This may support fairly steep lapse rates, which would foster moderate instability across portions of MS/AL amid supercell wind profiles. However, some uncertainty remains tied to the evolution of convection in the Day 3/Fri period into the morning hours of Saturday. Some forecast guidance suggests a relatively pristine warm sector will be maintained, or if only isolated convection develops overnight/early Saturday, recovery could occur. If this scenario unfolds, a concerning severe weather setup supporting all-hazard severe could unfold across portions of LA/MS/AL through the day and into evening, and eventually spreading east into GA overnight. Trends will be monitored closely over the coming days and further adjustments to the 30 percent/Enhanced risk area may be needed in future outlooks.
With northward extent, instability will become more limited. Nevertheless, sufficient moisture amid intense deep-layer flow will support swaths of strong/damaging winds into the Ohio Valley and portions of the central Appalachians Saturday and Saturday night. Higher outlook probabilities may be needed in subsequent outlooks if confidence increases.
..SEVERE WEATHER OUTBREAK POSSIBLE ON D4/SAT...
...DISCUSSION... ...Day 4/Sat - Central Gulf Coast States to the Ohio Valley...
A strong large-scale upper trough is forecast to quickly move across the Plains to the MS Valley on Saturday. An intense jet streak will move across the Deep South into the OH Valley as this occurs. At the surface, a low secondary to the 980 mb low over the Upper Midwest is forecast to develop during the late morning/early afternoon across the mid-South. This will aid in further northward transport of rich Gulf moisture into portions of the Lower MS Valley and TN Valleys. Atop this moisture-primed boundary layer, cold 500 mb temperatures are forecast. This may support fairly steep lapse rates, which would foster moderate instability across portions of MS/AL amid supercell wind profiles. However, some uncertainty remains tied to the evolution of convection in the Day 3/Fri period into the morning hours of Saturday. Some forecast guidance suggests a relatively pristine warm sector will be maintained, or if only isolated convection develops overnight/early Saturday, recovery could occur. If this scenario unfolds, a concerning severe weather setup supporting all-hazard severe could unfold across portions of LA/MS/AL through the day and into evening, and eventually spreading east into GA overnight. Trends will be monitored closely over the coming days and further adjustments to the 30 percent/Enhanced risk area may be needed in future outlooks.
With northward extent, instability will become more limited. Nevertheless, sufficient moisture amid intense deep-layer flow will support swaths of strong/damaging winds into the Ohio Valley and portions of the central Appalachians Saturday and Saturday night. Higher outlook probabilities may be needed in subsequent outlooks if confidence increases.