SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1247 AM CDT Sun Apr 16 2023 Valid 161200Z - 171200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE GREAT LAKES/OHIO VALLEY...SOUTH ACROSS THE CAROLINAS INTO PORTIONS OF THE FLORIDA PENINSULA.... ...SUMMARY... Marginally severe thunderstorms, associated with isolated damaging winds and hail will be possible in parts of the Southeast and Carolinas, northward into the Appalachians and southern Great Lakes. ...Lower Great Lakes/OH Valley/Middle Atlantic... Strongly diffluent high-level flow will develop across the Great Lakes/OH Valley early in the period ahead of a negative-tilt upper trough. Associated surface low is forecast to deepen and mature near Lake MI, moving very little through the period. Even so, surface front is forecast to surge into central OH by 18z then into western PA by 17/00z. Latest model guidance does not develop much instability across the warm sector with MLCAPE expected to remain less than 500 J/kg. Even so, boundary-layer heating will contribute to steep lower tropospheric lapse rates such that convective temperatures will be breached early in the period. Scattered convection should develop along/ahead of the front, initially over lower MI by late morning then into the OH Valley by early afternoon. Forecast soundings suggest gusty winds will be the greatest risk with this activity. Strong large-scale forcing should aid frontal convection as it propagates downstream through a weakly buoyant air mass. ...FL... Current water-vapor imagery depicts a weak mid-level short-wave trough within the base of the larger central US trough. This feature is currently over the western Gulf of Mexico and is forecast to progress into the central Gulf by 18z and approach the Gulf Coast of FL by 17/00z. 500mb flow should strengthen a bit across the peninsula ahead of this feature which should encourage boundary-layer convergence to focus across the eastern FL Peninsula. Forecast soundings suggest a fair amount of buoyancy with MLCAPE values on the order of 2500 J/kg and modest surface-6km bulk shear. Multi-cell convection should develop by 18z. A few weak supercells may also evolve within an expanding corridor of convection. Hail/wind are the main risks with this activity. ..Darrow/Squitieri.. 04/16/2023
