SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0300 PM CDT Thu Apr 10 2025 Valid 102000Z - 111200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE LOWER MISSISSIPPI VALLEY AND SOUTHEAST... ...SUMMARY... Scattered strong to severe thunderstorms are expected from portions of the lower Ohio Valley into the Southeast through this afternoon and evening. Large hail and damaging winds should be the main threats. ...20z Update... Ahead of the cold front moving across the OH/MS Valleys, strong heating has promoted gradual destabilization and multiple corridors of storm formation this afternoon. 70s and 80s F surface temperatures indicate the air mass is well-mixed with dewpoints generally in the 40s F. The relatively dry boundary layer should support efficient downward momentum transfer of stronger tropospheric winds, and a threat for scattered damaging winds. Some clustering and a stronger cold pool currently becoming established may focus this threat across the lower OH Valley into parts of TN/KY. Otherwise, isolated damaging gusts and some hail are possible. Across parts of the mid to lower MS valley, predominately cellular storms are expected late this afternoon continuing through the evening. Hail appears likely with these storms given the very favorable lapse rates aloft (8-9 C/km) and elongated hodographs favoring supercells. Some significant hail near 2 inches in diameter cannot be ruled out with the more robust rotating storms. Upscale growth overnight may foster a wind threat as one or more clusters/line segments spread east across AL and GA with damaging gusts. ..Lyons.. 04/10/2025 .PREV DISCUSSION... /ISSUED 1126 AM CDT Thu Apr 10 2025/ ...Lower Ohio Valley into the Southeast... Large-scale upper troughing is forecast to further amplify today over the eastern CONUS, as multiple embedded shortwave troughs rotate through its base. A lead shortwave trough will advance eastward over the upper OH Valley and central Appalachians through the day, while a trailing shortwave trough is expected to move southeastward across the mid MS Valley, lower OH Valley, and TN Valley through this evening. A weak/diffuse cold front is likewise forecast to develop southeastward across these regions through the day, providing some focus for thunderstorm development later this afternoon and evening. 12Z soundings across the Southeast indicate shallow/limited low-level moisture in place, but also relatively steep mid-level lapse rates. Strong daytime heating, gradual low-level moistening from the southwest, and cooling mid-level temperatures associated with the trailing shortwave trough should all aid in the development of around 1000-1500 J/kg of MLCAPE ahead of the front by mid afternoon. Weak low-level westerly winds are forecast to gradually veer and strengthen with height through the mid/upper levels, which will likely foster relatively long/straight hodographs and 40-55+ kt of effective bulk shear. This should easily support organized updrafts, including the potential for supercells. Current expectations are for robust thunderstorm development to occur over the lower OH Valley/Mid-South region by 18-20Z. This initial activity will likely be supercellular, with an associated threat for large hail given steep lapse rates aloft and strong deep-layer shear. Additional strong to severe thunderstorms should develop through the rest of the afternoon and early evening across a larger portion of the lower OH Valley into the TN Valley and Southeast. Any convection which can remain at least semi-discrete should pose a continued hail threat. Some tendency for upscale growth into multiple bowing clusters seems likely by late afternoon/early evening. A well-mixed boundary layer should support efficient downward momentum transfer and a threat for scattered damaging winds, before convection eventually weakens by mid/late evening with the loss of daytime heating.
