Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0300 AM CST Thu Nov 26 2020 Valid 291200Z - 041200Z ...DISCUSSION... It appears increasingly probable that a closed upper low over the southern Plains will merge with a northern-stream upper trough over the eastern CONUS on Day 4/Sunday, likely forming a highly amplified upper trough/low by Day 5/Monday. Medium-range guidance is in reasonably good agreement in depicting a deepening surface low developing from coastal LA Sunday morning northeastward to the Mid-Atlantic vicinity by Day 5/Monday. As greater low-level Gulf moisture advances inland across parts of the Southeast and Mid-Atlantic in tandem with the deepening surface low, weak instability may develop across the warm sector of this cyclone. Rapidly strengthening low and mid-level wind fields suggest that organized severe storms capable of producing at least isolated damaging winds may occur over parts of the Deep South into the Carolinas on Day 4/Sunday, and from the Carolinas into eastern portions of the Mid-Atlantic on Day 5/Monday. At this point, it remains very uncertain how much surface-based instability will ultimately develop across these regions, which will have a large impact on overall severe potential. This uncertainty precludes the introduction of 15% severe probabilities for now. However, the severe potential for this system will be reevaluated in later outlook updates. Once the cold front associated with this cyclone clears the East Coast, severe thunderstorm potential appears minimal across the CONUS on Day 6/Tuesday and Day 7/Wednesday.
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