Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Sun Apr 19 2026 Valid 221200Z - 271200Z ...DISCUSSION... A western trough will take hold in the days preceding this convective period. Ahead of this trough moisture will return northward through the central Plains, with 50F dewpoints reaching perhaps as far north as the Canadian border during Wednesday/Day-4. This return flow setup and western trough will set the stage for multiple days of severe weather potential. On Wednesday/Day-4, a lobe of vorticity will eject northeast out of the western longwave trough across the central and northern Plains. As this occurs, surface cyclogenesis should take place across the far northern Plains. To the south of this surface low, a dryline should sharpen across western Nebraska and Kansas. At the same time, vertical shear should strengthen as the shortwave moves northeast across the region. The kinematic profiles will support supercells initiating along the dryline. However, concerns remain about the quality of the moisture to the east of the dryline and subsequently as to the number of potential thunderstorms that may develop. This uncertainty precluded the introduction of unconditional 15% probabilities at this time. On Thursday/Day-5, the shortwave trough/midlevel low will deepen as it slowly moves north-northeast during the day. This will help maintain a strong surface cyclone across the northern Plains, with strong southerly winds advecting Gulf moisture northward to the east of the north-south oriented frontal boundary. Showers and thunderstorms will be possible along and east of the aforementioned frontal boundary across a large portion of the central US. Strong vertical wind shear across this frontal boundary will promote severe potential from Oklahoma northward to perhaps as far north as Minnesota. The northern extent of the severe potential will be delimited by the degree of moisture return, and have expanded the unconditional 15% probability area northward into Iowa to account for the increasing confidence in severe thunderstorm potential. Overnight Thursday/Day-5, a surface cold front, augmented by convective outflow, should push east across the northern and central Plains and south-southeast across the southern Plains. Another round of severe thunderstorms will be possible on Friday/Day-6 across portions of northeast Texas/northern Louisiana and much of Arkansas as diurnal heating of a moist airmass results in MUCAPE values between 1000-2000 J/kg beneath modest vertical shear associated persistent southwest midlevel flow. The severe potential will likely persist into Saturday/Day-7 and Sunday/Day-8 across portions of the southern Plains and northern Gulf Coast states. Here, persistent western troughing will maintain an increasingly moist airmass along and south of the aforementioned frontal boundary. The location of this frontal boundary will likely be significantly impacted by the repeated rounds of thunderstorms in the prior days. Model guidance is in general agreement that at least modest westerly/southwesterly flow will persist across the southern Plains, with episodic perturbations traversing this flow field downstream of the broader large-scale western trough. However, significant differences remain with respect to the timing, strength, and location of any of these perturbations to attempt to highlight unconditional severe probabilities.Read more
