SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1115 AM CDT Tue May 20 2025 Valid 201630Z - 211200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND TONIGHT FROM EASTERN ARKANSAS INTO MUCH OF THE TENNESSEE VALLEY AND THE SOUTHERN APPALACHIANS... ...SUMMARY... Multiple rounds of severe thunderstorms are expected today through this evening, centered on the Mid/Deep South, Tennessee/Lower Ohio Valleys, and Cumberland Plateau. Tornadoes, some of which could be strong, along with scattered to widespread damaging winds, and large to isolated significant severe hail will be possible. ...KY/TN... Thunderstorms are ongoing across central KY/middle TN. These storms will progress eastward through the afternoon into a moist and increasingly unstable air mass over eastern KY/TN and eventually into western WV/VA. Most model guidance suggests that storms will intensify through the day, with an increasing risk of damaging wind gusts and a few tornadoes. Refer to MCD #902 for further details. ...AR into the TN Valley this afternoon/evening... In the wake of the aforementioned convection, rapid heating is occurring across eastern AR/west TN/northern MS. Surface dewpoints in the upper 60s to 70s and steep mid level lapse rates will yield afternoon MLCAPE values around 3000 J/kg and only a weak cap. This will lead to the development of multiple clusters of intense thunderstorms (including supercells) that will track eastward through the afternoon and evening hours. The initial storms will pose a risk of very large hail and a few tornadoes. As the activity progresses eastward, the risk of damaging winds will increase with a persistent risk of tornadoes. Strong tornadoes will be possible. Storms are expected to get as far east as northwest GA tonight before slowly weakening. ...MO/IL... Satellite imagery shows a well-defined shortwave trough and associated surface low over IA/MO. Ahead of this feature, southerly low-level winds have transported mid 60s dewpoints into central IL, where strong heating is now occurring. This will result in moderate CAPE across the region and encourage rapid thunderstorm development over northeast and east-central MO by mid-afternoon. Steep lapse rates aloft and favorable deep-layer shear will support supercell structures capable of large hail, damaging winds, and a few tornadoes. Storms will track across IL and into central IN this evening. ..Hart/Moore.. 05/20/2025