SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Thu Apr 20 2023 Valid 221200Z - 231200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CAROLINAS AND FAR SOUTHEAST GEORGIA... ...SUMMARY... Thunderstorms associated with wind damage and hail will be possible on Saturday in the Carolinas and far southeast Georgia. A marginal severe threat could also develop in parts of Florida and in parts of Texas. ...Mid-Atlantic/Carolinas/Eastern Georgia/Florida... An upper-level trough will become negatively-tilted in the Great Lakes on Saturday, as a cold front moves quickly eastward across the southern and central Atlantic coastal states. Ahead of the front, moisture and instability will increase during the day. Thunderstorms will likely form along and ahead of the front relatively early in the day due to forcing associated with the upper-level system and cold front. It appears that a line of thunderstorms will develop in the higher terrain, and move eastward across Virginia, the Carolinas and southeast Georgia during the afternoon. Model forecasts suggest that the most favorable environment will be located in the eastern Carolinas, where forecast soundings at 21Z have MLCAPE in the 1200 to 1500 J/kg range, 0-6 km shear from 40 to 45 knots, and 0-3 km lapse rates near 7.0 C/km. This should be favorable for a wind-damage threat, associated with fast-moving multicell line segments. As storms gradually merge, a squall line is expected to form in the afternoon. This line will likely move into the western Atlantic during the early evening. Further to the south across Florida, isolated thunderstorms are expected to develop during the day. Instability is forecast to remain relatively weak, with large-scale ascent being limited. This should keep any severe threat marginal during the afternoon. A few strong wind gusts could occur with short multicell line segments. ..Southwest Texas... West-northwest mid-level flow will be in place across the southern Plains. At the surface, a cold front is forecast to move southward across west Texas. Ahead of the front, an axis of maximized low-level moisture is forecast to be in the Rio Grande Valley, where surface dewpoints could be in the lower 60s F. Isolated thunderstorm development will be possible in parts of southwest Texas as surface temperatures warm during the day. NAM forecast soundings Saturday afternoon have MLCAPE near 1000 J/kg, along with 0-6 km shear around 50 knots. This, combined with steep mid-level lapse rates could be sufficient for marginally severe storms. Hail and strong wind gusts are expected to be the primary threats. ..Broyles.. 04/20/2023
