SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0638 AM CDT Sat Sep 16 2023 Valid 161300Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS CENTRAL TX... ...SUMMARY... Isolated to scattered severe thunderstorms are possible across a portion of central to southeast Texas into this afternoon. Isolated severe thunderstorms are also possible over a part of the central Great Plains across the Mid-Mississippi Valley from 2 to 9 PM CDT. ...Central TX to the Middle TX coast... A small MCS over the TX Big Country/Concho Valley should continue southeast through at least central/south-central TX to midday. A confined corridor of strong to severe wind gusts from 50-75 mph will remain possible, especially near the track of the MCV. Weakening low-level warm advection this morning should foster some diurnal decay in intensity, but its attendant outflow may serve as a focus for an uptick in convective development later this afternoon towards the Middle TX coast. Still, weak mid-level lapse rates and relatively modest deep-layer shear should serve to marginalize hail sizes with locally strong gusts of 45-60 mph being the main hazard. ...Central Great Plains to the Mid-MS Valley... While the primary shortwave trough will move east across northern ON, a secondary impulse over southwest MN will track east-southeast into northwest IL by early Sunday. A surface cold front attendant to these features should arc from eastern WI through northern MO into southern NE by late afternoon. The degree of boundary-layer heating ahead of the front is somewhat uncertain given ongoing broken cloud coverage and some of fog/stratus. But with steepening mid-level lapse rates, a corridor of modest buoyancy with MLCAPE of 1000-1500 J/kg should develop. Deep-layer shear will be weak to the northeast of the Lower MO Valley, suggesting that 0.5-1 inch hail magnitudes will dominate. Mid-level northwesterlies will become more moderate across the NE/KS portion of the outlook area and may support hail of 0.75-1.5 inch along the western fringe of sustained storm development. In conjunction with greater potential for deeper boundary-layer mixing, localized strong to severe gusts of 45-60 mph will also be possible. These threats should weaken fairly abruptly after dusk given the lack of low-level mass response and nocturnal increase in MLCIN. ..Grams/Bunting.. 09/16/2023
