547 ACUS48 KWNS 230905 SWOD48 SPC AC 230904 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0404 AM CDT Thu Apr 23 2026 Valid 261200Z - 011200Z ...DISCUSSION... A multi-day severe weather event remains on track for Sunday/Day-4 evening through Monday/Day-5, with additional severe storms possible during the rest of the forecast period. A vigorous, yet compact, negatively tilted midlevel wave is forecast to move across the Southwest and eject into the Plains Sunday evening into Monday. As this wave ejects into the central US, strong surface cyclogenesis is expected over the Central Plains on Sunday evening. The flow around this low will help draw very rich boundary layer moisture northward to the east of a sharpening dryline. The atmosphere on Sunday across the Southern and Central Plains should remain capped for much of the day, allowing extreme instability (SBCAPE/MUCAPE values in excess of 4000 J/kg) to develop. As modest height falls overspread the dryline during the late afternoon and evening hours, the expectation is that at least a few storms will be able to break through the cap. While 20260423/00Z global guidance is still struggling to produce widespread precipitation along and east of the dryline, the control members are now at least producing light QPF along the dryline which would tend to support the idea that isolated convection will be possible. The environment to the east of the dryline will be very unstable and increasingly sheared as enhanced midlevel flow overspreads the warm sector. Additionally, as the surface low deepens during the evening hours, low-level winds will respond by rapidly increasing to greater than 50 knots. The result will be the potential for any thunderstorm that develops and sustains itself to become strong supercells capable of producing all severe hazards, including significant severe. As the main wave continues to lift northeast on Monday, the surface low should rapidly move from the Central Plains into the Upper Mississippi Valley. As this occurs, a surface warm front will rapidly lift northward on the nose of an intense low-level jet. This low-level jet will likely result in widespread precipitation to the north of the front, which will have impacts on the northern extent of Monday afternoon's severe potential. By Monday afternoon, additional thunderstorms are expected to develop along and east of an advancing dryline/cold front in an increasingly unstable atmosphere. Diurnal heating of a boundary layer with low-to-mid-60Fs dewpoints should result in SBCAPE/MUCAPE values between 2000-3000 J/kg. Additionally, vertical shear will remain more than sufficient for supercells. All severe hazards will remain possible with this convection, with the greatest concentration of severe storms likely across the Mid-Mississippi Valley where a 30% area was introduced. Monday evening into the overnight hours will see a continued potential for severe storms as the surface front pushes east into the western portions of the Ohio Valley. Additionally, severe storms will likely continue across the southwest portion of the front, which will slowly begin to stall in a southwest-to-northeast or west-to-east configuration across Arkansas into Kentucky. Additional severe storms will be possible Tuesday/Day-6 through Thursday/Day-8 across the Southern and Central Plains into the Lower-to-Middle Mississippi Valley as cyclonic midlevel flow persists atop a moist boundary layer with a frontal boundary somewhere across the area. However, given the uncertainties in how the convective evolution of Sunday and Monday will impact the location of relevant surface features and the general uncertainty associated with identifying the timing of midlevel perturbations embedded within the broader scale cyclonic midlevel flow, unconditional 15% severe probabilities will be deferred to subsequent outlooks. ..Marsh.. 04/23/2026