SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1237 AM CST Sat Dec 27 2025 Valid 281200Z - 291200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN MO/AR TO THE OH AND TN VALLEYS... ...SUMMARY... A low-probability severe thunderstorm threat is forecast from Sunday afternoon into Sunday night from Missouri-Arkansas into the Ohio and Tennessee Valleys. ...MO/AR to the OH/TN Valleys... Phasing of multiple shortwave impulses will support amplification of an upper trough, mainly on Sunday night, as it progresses from the High Plains to the Great Lakes. This will induce deepening of a surface cyclone from the Lower MO Valley towards Lake Huron. Attendant cold front will accelerate Sunday night as it quickly sweeps east into the Upper OH Valley and south into the northwest Gulf by 12Z Monday. Isolated to scattered elevated thunderstorms are most likely on Sunday morning across parts of the Mid-MS Valley to the southern Great Lakes within a strengthening low-level warm conveyor. It is plausible that a few updrafts might weakly rotate, but meager buoyancy atop the stable surface and cluster convective mode appears supportive of only small hail. Primary forecast challenge is the degree of surface-based destabilization by Sunday afternoon, which will largely influence tornado and severe thunderstorm wind potential. Latest guidance remains split into two paths. This evening's RRFS/RAP/HRRR/HRW-ARW suggest that a plume of meager buoyancy with MLCAPE up to 500 J/kg should become established ahead of a cold front across the Ozarks to a portion of the Mid-MS Valley near the surface cyclone by afternoon. Meanwhile the NAM and HRW-NSSL indicate little to no surface-based buoyancy in the warm-moist sector along the front. Guidance consensus does suggest at least a low-topped, thin QLCS should become established along the front from IL/IN towards AR by early evening. The progressive nature of the front along with the paucity of surface-based instability downstream renders large uncertainty in whether lightning-producing convection will be maintained Sunday night along the front. However, kinematic fields will become increasingly impressive, with strong gusts likely accompanying low-topped convection along the front. CAM consensus though is for convection to wane early morning Monday as instability remains negligible. As such, have maintained the prior level 1-MRGL risk for wind, with a subset of low tornado probabilities from MO to IN. ..Grams.. 12/27/2025
