SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0720 AM CDT Fri Mar 14 2025 Valid 141300Z - 151200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS THE MID-MISSISSIPPI VALLEY AND PORTIONS OF THE LOWER OHIO VALLEY AND MID SOUTH... ...SUMMARY... A regional outbreak of severe storms is likely across the Mid-Mississippi Valley to the Lower-Mississippi Valley, including portions of the Lower Ohio Valley and Mid South. Tornadoes, several of which could be strong, widespread severe gusts ranging from 60 to 100 mph, and scattered large hail up to baseball size will be possible. ...Synopsis... Water-vapor satellite imagery shows a powerful negatively tilted mid to upper-level shortwave trough over the Four Corners into the southern High Plains. A very intense 500-mb speed max in excess of 100+ kt will round the base of the trough and quickly move northeastward across OK this afternoon and near Lake Michigan late tonight. The associated 12hr mid-level height falls (on the order of 240-270m) will overspread portions of the central U.S. as a deep cyclone develops northeast from the central High Plains into the Upper Midwest. In the low levels, a dryline will surge across the central Plains eventually arcing from the low southeastward into the Ozarks. Strong boundary-layer heating is forecast ahead of the cyclone and initial storms will likely develop by early afternoon (18-20z) from eastern NE southward into eastern KS/western MO. Storms will quickly grow upscale into a fast northeastward-moving band of storms posing a risk for all hazards as this activity moves into IA and towards the MO/IA/IL border region. Intense thunderstorm straight-line gusts peaking locally in the 80-100 mph range are possible with the stronger cores/inflections in the band as it matures and moves across the Mid MS Valley and eventually into the southwestern Great Lakes tonight. Have made some adjustments for higher wind/tornado probabilities over northern IL eastward into the Michiana region late tonight. Additional severe storms will develop southeast along the wind shift into MO and within the northern periphery of richer low-level moisture from southeast MO southward into eastern AR and into northern MS/western TN. Stronger high-level flow over the Mid South will promote more discrete supercell structures. Recent model guidance indicates at least widely scattered storms developing towards the evening as far south as the MS/AR/TN border region. Forecast soundings strongly favor intense supercells capable of large to very large hail and potentially a few strong tornadoes this evening and perhaps continuing into the late evening. Forcing for ascent will be more nebulous farther south into the Gulf coastal plain late. However, model guidance continues to suggest at least isolated supercell development may occur within an increasingly rich and weakly capped boundary layer overnight. Have likewise extended 10-percent significant tornado probabilities farther south into southern MS to account for this forecast scenario. Moderate buoyancy and enlarged hodographs will support a supercell tornado risk with this activity with it perhaps continuing into early Saturday morning. ..Smith/Thompson.. 03/14/2025
