1PM Day 1 Convective Outlook for Wednesday, March 4. THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM NORTH TEXAS/EASTERN OKLAHOMA TO OZARKS AND LOWER OHIO VALLEY
SUMMARY
Isolated to scattered severe thunderstorms are expected through tonight from north-central Texas and eastern Oklahoma to the Ozarks and Lower Ohio Valley. Large hail, localized wind damage, and a tornado or two are possible.
20z Update
Only minor adjustments were made to remove the Marginal Risk across a small portion of eastern KS/central MS/central IN where morning convection has overturned the environment. Otherwise, the Slight Risk across from north Texas to the Ozarks and Lower Ohio River Valley continues. See previous discussion below for more information.
Southern Plains to the Ozarks and Lower Ohio Valley
Well in advance of an amplifying trough over the Great Basin, a low-amplitude southern-stream shortwave trough over the south-central High Plains will continue east-northeastward over the Lower Missouri Valley through tonight. A base-embedded modestly increasing belt of southwesterly mid-level flow (50+ kt) will maximize from northeast Oklahoma/southeast Kansas across the Ozarks, in general proximity to a weak surface low/frontal zone across the region where deep-layer/low-level shear are expected to be maximized.
South of the front, southerly low-level flow will support dewpoints climbing into generally the low to mid 60s F. While cloud cover may remain semi-prevalent across the warm sector, this increasing moisture beneath steep mid-level lapse rates amid filtered daytime heating should support MLCAPE values generally around 1000-1500 J/kg in a narrow corridor along/ahead of the front. Locally greater instability should develop across north-central into central Texas where stronger daytime heating is expected, although deep-layer/low-level shear will be notably weaker, while still sufficient for relatively isolated severe storms.
Across most of the Slight Risk area, effective bulk shear of 35-50 kt will easily support organized convection regionally, although convective mode may tend to be somewhat messy given broad ascent within the modest low-level warm advection regime near the surface front. Additionally, ongoing mostly elevated convection this morning across northeast Oklahoma into southern Missouri and southern Illinois may hamper stronger heating and limit destabilization downstream, with outflow/existing convection contributing to modal complexity later today.
Even with these potential limitations, a broad area of isolated to scattered severe thunderstorm potential exists through tonight. An isolated and/or occasional hail threat may persist with ongoing elevated convection from southern Missouri into southern Indiana/northern Kentucky. Surface-based thunderstorm development should otherwise become more probable across the Ozarks into mid/late afternoon closer to the surface front/surface low and modifying outflow. A mix of supercells and clusters will pose a risk for large hail. Damaging winds will also be possible where steepened low-level lapse rates can develop with daytime heating. Although low-level flow is not forecast to become overly strong, there should be sufficient 0-1 km SRH to support some threat for a couple of tornadoes with any sustained supercells/clusters, particularly across southern Missouri and northern Arkansas.