Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0352 AM CST Mon Feb 15 2021 Valid 181200Z - 231200Z ...DISCUSSION... A highly amplified upper trough should continue moving eastward from the Plains across much of the MS/OH/TN Valleys and Southeast on Day 4/Thursday. A related surface low is forecast to develop northeastward across the central Gulf Coast states and towards the vicinity of SC by Thursday evening. Greater low-level moisture and a warm sector should likewise develop northward over portions of the FL Panhandle, southeastern AL, and southern/central GA through the day. Rather strong low- and mid-level flow appears likely to overspread these areas, and deep-layer shear will easily support organized severe convection. Strong to severe storms may be ongoing Thursday morning across the western FL Panhandle/southern AL vicinity near the surface low. Current expectations are for these storms to move quickly east-northeastward on Thursday across the developing warm sector. Both damaging winds with a possible squall line and a couple tornadoes with any supercells either ahead of or embedded within the line may occur given a favorable veering/strengthening low-level wind profile and sufficiently unstable airmass. With a consistent signal in guidance depicting this scenario, have included a 15% severe area for Day 4/Thursday where surface-based storms appear probable. Some severe risk may extend northeastward into parts of the Carolinas Thursday evening/night. However, too much uncertainty currently exists regarding the degree of boundary-layer instability to extend the 15% severe probabilities any farther northeastward. Once the cold front associated with the surface low clears the East Coast, potentially late Thursday night or early Day 5/Friday, then the severe risk across the CONUS appears negligible through the remainder of the extended forecast period.
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