Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
508 ACUS48 KWNS 230859 SWOD48 SPC AC 230857 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0357 AM CDT Thu May 23 2024 Valid 261200Z - 311200Z ...DISCUSSION... ...Day 4/Sun - Ozarks, Mid-MS/Lower OH/TN Valleys... A regional severe weather episode is expected on Day 4/Sunday. Significant severe thunderstorms capable of all hazards will be possible. An upper trough will overspread the region, resulting in a corridor of strong southwesterly mid/upper flow overlapping a very moist and strongly unstable airmass. Forecast guidance depicts a 700 mb southwesterly jet around 45-60 kt over the Mid-MS/Lower OH Valley vicinity. Meanwhile, a surface low near northeast KS/northwest MO at the beginning of the period will deepen as it lifts northeast toward Lake Michigan through the evening. A cold front will develop east across the region from late afternoon into the overnight hours. Ahead of the front, mid/upper 60s F dewpoints are expected. Steep midlevel lapse rates atop this moist boundary layer will support strong destabilization. Convection will likely be ongoing Sunday morning across parts of the Mid-MS/Lower MO Valley. The evolution of this activity is a bit uncertain, but may continue to develop east along a warm front draped across northern IL/IN. Additional convection is expected across the warm sector from southeast MO/northwest AR eastward into TN/KY. While storm mode/evolution remains a bit uncertain at this time (may be a mix of supercells and more linear convection), supercell wind profiles coupled with favorable thermodynamics will support all-hazards severe potential across a broad area during the day and into the nighttime hours. ...Day 5/Mon - Mid-Atlantic to the Southeast... Spread among forecast guidance increases considerably on Monday and various models evolve the central U.S. upper trough quite a bit differently. If a more progressive system prevails, favorable vertical shear and large-scale ascent will overspread parts of the Mid-Atlantic vicinity (decreasing with southward extent into the Southeast). Severe-storm potential may develop ahead of an east/southeastward-advancing cold front if this scenario unfolds. However, uncertainty precludes introduction of 15 percent severe probabilities at this time. ...Days 6-8/Tue-Thu... Forecast spread increases further late in the period. Overall severe potential appears to wane for much of the CONUS during this time, but predictability is low. ..Leitman.. 05/23/2024