Storm Prediction Center Day 4-8 Severe Weather Outlook Page (2024)

SPC on Facebook

@NWSSPC

NCEP Quarterly Newsletter

 ZCZC SPCSWOD48 ALL ACUS48 KWNS 190849 SPC AC 190849 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0349 AM CDT Sun May 19 2024 Valid 221200Z - 271200Z ...DISCUSSION... ...Day 4/Wed - Southern Plains to the Ohio Valley... An upper low over the Upper Midwest will develop east/northeast across the Great Lakes and Ontario on Wednesday. A broad area of enhanced mid/upper southwesterly flow will persist across the region. At the surface, strong low pressure over MN/WI will occlude and slowly pivot north/northeast into Ontario. A cold front will shift east across Lower MI/IL/IN, while the southern extent of this boundary stalls, or returns a bit north from southern MO into OK/northwest TX. Convection may be ongoing Wednesday morning along the cold front, with destabilization ahead of the boundary across the Ohio Valley occurring during the day. Further south, convective evolution is more uncertain. However, a very moist and unstable airmass is expected. Thunderstorms may be ongoing during the morning and persist as an MCS through the afternoon, or convection may develop along a surface dryline or residual outflow. While some uncertainty remains in details, a corridor of severe potential appears likely given the presence of a surface boundary, sufficient vertical shear, and a moist/unstable boundary layer. ...Day 5/Thu - Southern Plains/ArkLaTex and the central Appalachians/Mid-Atlantic vicinity... A subtle upper shortwave impulse is forecast to eject from the southern Rockies/northern Mexico toward the Mid-South vicinity on Thursday. As this occurs, a surface dryline will surge east, becoming positioned from near the OK/TX border southward into central TX by evening. A very moist and unstable airmass will be in place ahead of the dryline and convection is likely. With time an MCS may develop and move southeast across the risk area during the evening hours. Meanwhile an upper low over Quebec and attendant trough will overspread much of the northeastern U.S. on Thursday. A surface cold front is expected to develop southeast across the area and a line of thunderstorms may pose some severe risk to the region. Confidence in the location of 15 percent severe coverage is low, precluding probabilities at this time. ...Days 6-8/Fri-Sun... Lower-amplitude and generally weaker flow is expected across much of the CONUS on Friday and Saturday. A seasonally moist airmass will persist across the southern Plains to the Mid-MS Valley during this time, and a weak shortwave impulse migrating through westerly flow aloft may be a focus for strong to severe storms across parts of the Plains/MO Valley. However, spread among guidance is fairly large and confidence is low. By the end of the period on Sunday, some guidance suggests a strong upper shortwave trough will eject into the southern Plains. However, guidance varies in the timing of this feature (some on Saturday, some on Sunday) as well as in the strength of the trough, resulting in low predictability. ..Leitman.. 05/19/2024 CLICK TO GET WUUS48 PTSD48 PRODUCT