SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 AM CST Tue Dec 22 2020 Valid 241200Z - 251200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS FAR EASTERN SC...COASTAL NC...AND FAR SOUTHEAST VA... ...SUMMARY... Isolated severe thunderstorms are possible across portions of the Florida Panhandle and adjacent southeast Alabama and southwest Georgia early Thursday. Severe thunderstorms are also expected across the Mid-Atlantic States Thursday afternoon and evening. ...Synopsis and Discussion... Deep upper troughing is forecast to extend from northwestern Ontario into central Mexico early Thursday morning. Strong flow aloft will extend throughout the periphery of this upper trough. Shortwave trough embedded within the base of this larger trough will likely be moving through the Ozark Plateau and southern Plains early Thursday morning. Continued eastward/northeastward progression of this shortwave is expected, with the parent upper trough also progressing eastward. Evolution of the embedded shortwave will help induce a neutral tilt to the upper trough by Thursday afternoon, and a slightly negative tilt and closed upper circulation over the OH Valley by late Thursday night/early Friday morning. The maturing process of the upper trough will also result in further strengthening of the winds throughout its periphery. By early Friday morning, 100+ kt 500-mb winds will likely extend from the mid MS Valley southeastward/eastward through the base of the trough over the Southeast and then back northeastward into the Northeast. Very intense low-level flow is also expected, with 60+ kt at 850-mb extending from the Carolinas through the Mid-Atlantic into Quebec. Modest severe potential is anticipated early Thursday along and ahead of the across the FL Panhandle and southeast AL/southwest GA. In this region, modest instability and strong flow will likely support a few strong/severe storms. An additional area of potentially greater severe potential is expected farther north across the Mid-Atlantic. In this area, a deepening surface low and strong low-level flow will contribute to robust moisture return as well as large, looping low-level hodographs. Strong buoyancy is not expected, but given the very strong vertical shear, even modest surface-based instability will likely result in severe storms. Strong to severe storms along the front appear likely, with some potential for warm-sector storms as well. Given the anticipated kinematic environment, any deeper warm-sector storms would likely become supercellular. ..Mosier.. 12/22/2020
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