11AM Day 2 Convective Outlook for Friday, March 6. THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS IN EASTERN KS/OK AND WESTERN MO/AR
SUMMARY
Scattered severe thunderstorms are expected from late afternoon Friday through Friday night from parts of the southern Great Plains to the Midwest. The greatest potential for a couple strong tornadoes and isolated very large hail is across eastern portions of Oklahoma/Kansas and western portions of Arkansas/Missouri.
Synopsis
Broad upper trough over the West should split into two distinct impulses by Friday night. The leading shortwave trough should eject from the Four Corners across the central Great Plains to the Upper Mississippi Valley, while a backside cutoff low evolves southward over the Lower CO Valley. Lead cyclone should track from the western KS vicinity across IA to the Upper Great Lakes. The dryline should mix towards central OK/TX through late afternoon. A surface cold front will accelerate southeastward across the central/southern Great Plains on the backside of the lead cyclone.
Central/southern Great Plains into the Midwest
Overall forecast has substantial uncertainties as latest guidance trends towards a more bimodal and less robust setup across the level 3-ENH risk vicinity. The most probable signal is for initial mid to late afternoon storm development to occur near the surface cyclone track in KS across the adjacent MO Valley. Strong deep-layer shear will support supercells near the immediate triple-point region and downstream warm conveyor, with primary risks of large hail and a couple tornadoes. But convection should grow upscale relatively quickly along the surface warm front, as well as the accelerating cold front. One elongated QLCS or a pair of QLCSs may evolve during the evening. The lead one should progress east-northeast towards the Lake MI vicinity with a threat for mainly damaging winds and a few embedded tornadoes, along the northern periphery of the surface-based instability plume. Farther south, the cold frontal QLCS should expand southwestward and progress more east-southeast. A mix of large hail, damaging winds, and perhaps a couple embedded tornadoes are plausible. But increasingly veered low-level winds near the front should taper the threat overnight.
A separate region of low-level warm conveyor storm development is evident downstream of the OK/TX dryline, mainly along a portion of the Red River towards the Ozarks during the late afternoon to early evening. Low-level and deep-layer shear profiles will be conditionally favorable for discrete supercells, amid a richly moist boundary layer and sufficiently steep mid-level lapse rates. With near-neutral mid-level height falls and peripheral influence of the mid-level jetlet farther to the west/northwest, confidence is below average on longer-lived/stronger supercells becoming sustained. Have shifted the level 3-ENH risk to be centered on this region, where storm development at least appears increasingly probable on Friday night.
West TX
Consensus of CAM guidance indicates an overnight corridor of storm development to the cool side of the accelerating cold front as it impinges on the western lobe of the TX buoyancy plume. Rather steep mid-level lapse rates and strong effective bulk shear could support a corridor of elevated large hail. The undercutting nature of the front suggests this corridor will remain spatially confined.