11AM Day 2 Convective Outlook for Wednesday, March 4. THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM NORTH TEXAS TO THE SOUTHERN MISSOURI AND ILLINOIS
SUMMARY
Isolated to scattered severe thunderstorms are expected during the afternoon and evening on Wednesday from north-central Texas and southeast Oklahoma into northwest Arkansas, southeast Missouri and southern Illinois. Large hail and occasional wind damage will be the primary threats.
Southern Plains to lower OH Valley
A midlevel shortwave trough now over CO will progress eastward and reach the mid MS Valley by early Thursday, in response to an amplifying wave upstream over the Great Basin/CA. An associated weak surface wave will develop east-northeastward along a quasi-stationary baroclinic from the Ozarks to the lower OH Valley, and this baroclinic zone will serve as the primary focus for ascent and convection Wednesday into early Thursday. Boundary-layer dewpoints in the 60s will be prevalent along and south of the front by tomorrow, given the returning moisture already present from southeast OK into MS. The low-level moistening will occur beneath the eastern extent of an elevated mixed layer with 7-8 C/km midlevel lapse rates, per 12z soundings across the southern Plains. Surface heating in cloud breaks will contribute to MLCAPE near 1000 J/kg with diminishing convective inhibition along the front through the afternoon.
Elevated convection could be ongoing at the start of the period across southeast KS/northeast OK in a zone of low-level warm advection. Storms will spread east-northeastward through the day toward southeast MO/southern IL and vicinity, while additional storms are probable along the front during the afternoon/evening from central/north TX into eastern OK/western AR. Deep-layer and low-level vertical shear will be sufficient for storm clusters and some supercell structures by late afternoon/evening closer to the path of the weak cyclone and midlevel trough across southern MO, where there will be the potential for large hail, damaging gusts, and a couple of tornadoes. Deep-layer shear will be weaker farther to the southwest toward TX where storms should be more isolated/discrete with an accompanying threat for large hail. Convection may persist through the overnight hours to the immediate cool side of the front.