Ah, so greater intraseasonal variability can anecdotally mask itself as seasonal shift? I could understand that if SD for "severe weather index" increases alongside with mean temperature increases, the window in which significant winter events may occur will expand even if it's an evenly-distributed warming.
That said, I've read a few papers which predict that even in the next 50 years, N/S jet orientation is not predicted to move northward in spring, while it is for other seasons.