Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0323 AM CDT Sun Apr 20 2025 Valid 231200Z - 281200Z ...DISCUSSION... A low-amplitude southwesterly flow regime will prevail for much of the Day 4-8 period across portions of the central and eastern U.S., with a mean upper trough persisting across the western states. Persistent south/southeasterly low-level flow across the Gulf and southern Plains will result in northward transport of rich boundary-layer moisture across the southern and parts of the central Plains through at least Day 6/Fri. Forecast guidance suggests weak shortwave impulses may float through modest southwesterly flow Days 4-5/Wed-Thu, perhaps providing some support for isolated to scattered thunderstorm potential across the warm sector over TX/OK/KS. Given a moist and unstable airmass, at least some severe potential will exist. However, where exactly severe potential may develop Day 4-5/Wed-Thu is uncertain given a lack of stronger large-scale ascent and absence of any substantial surface cyclogenesis, coupled with modest deep-layer flow. This precludes 15 percent probabilities at this time, though outlook areas could become necessary in later outlooks as smaller-scale features become better resolved. A period of weak upper ridging may spread across the Plains and the eastern U.S. on Days 6-7/Fri-Sat ahead of a more substantial upper trough developing over the western U.S. This may limit severe potential late in the week before the western upper trough ejects east toward the end of the forecast period.