Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0345 AM CST Tue Feb 23 2021 Valid 261200Z - 031200Z ...DISCUSSION... Medium-range models continue to suggest that, although blocking may linger to some degree through much of this period, an initially prominent mid-level high and amplified ridging across the eastern Pacific will become suppressed by a series of short wave perturbations emerging from the upstream Pacific. As this occurs, it still appears that a more pronounced split flow will evolve downstream, across much of the U.S. and southern Canada. This may include mean mid-level troughing in the southern branch, across the southern Pacific coast through the Southwest, from which one or two significant perturbations may emerge late this weekend into early next week. At the same time, subtropical ridging, centered over the southern Gulf of Mexico, may undergo a period of amplification, and a deep mid-level low near/north of Hudson Bay may maintain some influence, before perhaps returning northward across the Arctic Circle vicinity by the end of the period. This pattern could include potential for significant surface cyclogenesis to the lee of the southern Rockies and a substantive return flow of moisture off the western Gulf of Mexico by early next week, accompanied by at least some increase in risk for severe weather. However, based on sizable differences evident among the various models, and from run to run, the predictability of the short wave developments throughout this period appears relatively low.
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