Subj : DAY1SVR: Day 1 Convective To : All From : Mike Powell Date : Sat Apr 22 2023 07:17:00 ACUS01 KWNS 220602 SWODY1 SPC AC 220600 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Sat Apr 22 2023 Valid 221200Z - 231200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE CAROLINAS INTO THE MID ATLANTIC...AND ACROSS PARTS OF THE TX HILL COUNTRY AND EDWARDS PLATEAU... ....SUMMARY... Scattered severe storms capable of damaging gusts, hail, and a couple of tornadoes are possible today from the Carolinas into parts of the Mid Atlantic and Northeast. A few severe storms are also possible across parts of the Texas Hill Country and Edwards Plateau, with a risk of very large hail, isolated severe gusts, and possibly a tornado or two. ....Synopsis... A deep upper trough covering much of the central/eastern CONUS is forecast to take on a negative tilt later today, as a notable shortwave moves through the base of the trough toward the Mid Atlantic region. A surface cyclone is forecast to move from the lower Great Lakes toward western Quebec, as an attendant cold front moves toward the Eastern Seaboard. The western extension of this front will become nearly stationary across the northern Gulf of Mexico, and begin moving northward across Texas as a warm front during the day today. Another cold front will move southward through the Great Plains today, and overtake the old front across Texas by this evening. ....Mid Atlantic/Northeast southward into the Carolinas... An extensive band of convection will likely be ongoing at the start of the period from the southern Appalachians into the lower Great Lakes region. Modest diurnal heating ahead of this band will result in some destabilization. MLCAPE of 1000-1500 J/kg is expected to develop from southeast VA into parts of the Carolinas, decreasing with northward extent to less than 500 J/kg across northern portions of the Mid Atlantic and Northeast. Meridional mid/upper-level flow will likely result in messy convective mode, with a mixture of clusters, bowing segments, and possibly a few embedded supercells possible. For the Delmarva area and northward, locally damaging gusts will likely be the primary threat, though backed surface winds and increasing low-level shear/SRH may support a tornado or two as well. From the Tidewater region into portions of the Carolinas, stronger instability will support a greater hail threat, in addition to a risk of locally damaging gusts and a couple of tornadoes. At least the southern portion of the Slight Risk area may also see multiple rounds of storms, with prefrontal convection through midday and robust redevelopment along the cold front possible by mid/late afternoon. ....TX Hill Country/Edwards Plateau and vicinity... Uncertainty remains regarding storm coverage this afternoon and evening, but a few supercells capable of very large hail and isolated severe gusts appear possible. Modest low-level moisture return is expected across parts of west/central TX today, in advance of the cold front moving southward down the Great Plains. Moderate to locally strong buoyancy (MLCAPE of 1500-3000 J/kg) will develop where dewpoints rise into the upper 50s/lower 60s F amid relatively strong diurnal heating. Large-scale ascent appears subtle at best, but isolated storm development will be possible near the warm front by late afternoon, with some increase in coverage possible this evening as the reinforcing cold front moves southward across the region. Low-level southeasterly flow veering to west-northwesterly aloft will support 50-70 kt of effective shear, with elongated hodographs and favorable buoyancy supporting a threat of very large hail with any mature supercells. While low-level flow/shear will likely remain rather weak, a tornado also cannot be ruled out with any stronger supercell, especially near the surface boundary. Depending on the coverage of initial supercell development and the evolution of possible storm interactions, some upscale growth is possible this evening, and a southward-moving cluster could reach southern portions of the TX Hill Country tonight, with an attendant severe wind/hail threat. Additionally, strong storms which develop over northeast parts of Coahuila may spread east of the Rio Grande tonight, though the usual uncertainties remain regarding the evolution of nocturnal convection across that region. ...Dean/Squitieri.. 04/22/2023 $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .