Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0732 AM CDT Sat Apr 18 2026 Valid 181300Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE UPPER OHIO VALLEY TO THE APPALACHIANS... ...SUMMARY... Scattered strong to severe thunderstorms capable mainly of damaging winds will be possible today across the upper Ohio Valley and central Appalachians. ...Synopsis... Water-vapor imagery this morning shows a large-scale upper trough over the Upper Midwest into the south-central Plains. An elongated mid-level vorticity lobe and associated speed max will quickly move eastward across the Midwest today and reach the Lower Great Lakes and upper OH Valley late tonight. Farther south, a belt of strong west-southwesterly flow associated with a subtropical jet will reside over TX. A cold front extending from a low near James Bay southward through the Great Lakes and into TX will continue to push east and southeast through the period. Convective outflow over the OH Valley to the east of the front will eventually be overtaken by the front later today as a band of showers/thunderstorms develops over the upper OH Valley by early afternoon. ...OH Valley into the Appalachians... Some heating combined with a gradually moistening airmass (55-60 deg F surface dewpoints) will result in weak destabilization by midday as convective development ensues near the preceding outflow/wind shift and front. Ample mid to high-level flow will aid in some potential for storm organization, mainly in the form of a few stronger cells and linear bands. Widely scattered strong to severe gusts capable of wind damage will likely be the primary hazard, but an isolated risk for hail or a brief tornado is possible with the strongest cells. This activity will likely weaken by early evening as it encounters a slightly drier and less unstable airmass with east extent. ...Central Texas... Scattered showers and elevated thunderstorms are expected throughout much of the day as the cold front rapidly undercuts a moist and unstable air mass. The 12 UTC Del Rio, TX raob shows an 8.2 deg C/km 700-500 mb lapse rate. Forecast soundings show MUCAPE parcels rooted in the 850-700 mb layer, with effective deep-layer shear of 50-60 kt. Although an isolated risk for large hail appears to be the main hazard with the stronger cells, there has been some indication that a localized risk for severe gusts could accompany the strongest cores. For short-term details regarding a risk for hail/wind with a few stronger thunderstorms this morning extending from the Concho Valley east-northeast towards DFW, reference MCD #490. ..Smith/Dean.. 04/18/2026Read more