Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0356 AM CST Thu Feb 26 2026 Valid 011200Z - 061200Z ...DISCUSSION... Early in the forecast period a transition across the western US will take place as the low-amplitude ridge over the Great Basin/Southwest shifts eastward, giving way to an amplifying trough over the West. Several speed maxima are forecast to traverse the flow while it remains primarily northwesterly over the central US early in the period. At the surface, uncertainty remains regarding the southern extent of the arctic front pushing into the Plains on Day 3. Uncertainties in the position of this front will cause low confidence in the projected quality of the low-level moisture recovery across the southern Plains through Tuesday. As the upper-air pattern across the central US transitions from northwesterly to southwesterly, and return flow commenses, the shallow nature of the modified arctic airmass may initially limit the northward penetration of the richest theta-e air. As the period progresses into Wednesday and Thursday, ensemble guidance remains in general agreement regarding the transition to an amplified western trough and central-to-eastern ridge. However, the timing and phasing of individual shortwaves moving into the Plains remains a source of forecast uncertainty. The first meaningful shortwave is forecast to eject into the Plains early Wednesday, inducing surface cyclogenesis that should support a northward advancement of the warm sector. Any severe risk with this trough on Wednesday (Day 7) will be predicated on the evolution of the moisture return on prior days. On Thursday, a second, more potent trough is forecast to approach the Plains. Current ensemble guidance shows quite a bit more variance with the timing, amplitude, and evolution of this second trough. Some guidance brings this wave out as single, potent trough, with other guidance suggesting a series of more subtle shortwave troughs ejecting into the Plains from Thursday into Saturday. These discrepancies will have an impact on the location, timing, and magnitude of any potential severe weather threat. Despite these timing differences, the synoptic setup (increasing low-level moisture, strengthening southwest flow aloft, repeated cyclogenesis) is favorable for organized severe weather over the Plains and lower Mississippi Valley. While the severe weather threat should increase by Wednesday and Thursday (Days 7 and 8), the specific orientation of frontal boundaries and the northward extent of the moisture return will be highly dependent on the evolution of the upper-lows. Given that models tend to struggle with handling the details of pattern changes, will hold off on trying to highlight any specific corridor for severe probabilities for Wednesday and Thursday at this time.Read more
