Subj : DAY1SVR: Day 1 Convective To : All From : Mike Powell Date : Thu May 11 2023 15:31:00 ACUS01 KWNS 111955 SWODY1 SPC AC 111953 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0253 PM CDT Thu May 11 2023 Valid 112000Z - 121200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS KANSAS INTO SOUTHERN OKLAHOMA... ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SOUTHEAST LOUISIANA INTO SOUTHERN MISSISSIPPI... ....SUMMARY... Scattered severe thunderstorms remain possible into this evening across parts of the Great Plains centered on Kansas and Oklahoma. The greatest threat for a couple strong tornadic supercells should exist across central and southern Oklahoma between 5 to 9 PM CDT. Isolated severe storms including a couple of tornadoes and damaging winds are also expected across the Lower Mississippi Valley. ....Kansas into Oklahoma... The severe threat continues across much of KS where an arcing band of convection has developed from northwest to southern/southwestern KS. Reflectivity/velocity data from regional radars show some cells taking on supercellular characteristics with persistent mesocyclones, including at least one reported tornado. So while the overall kinematic environment appears somewhat marginal based on latest RAP mesoanalyses (effective SRH values 100 m2/s2 or less), the environment is conducive for organized convection, and should remain so through the evening as the nocturnal jet strengthens after 00 UTC. Further south, a residual cold pool across central to northern OK from early-morning convection has introduced considerable uncertainty into the severe weather potential. While an intense storm or two remains possible across north-central OK to southern KS, confidence in the tornado potential has diminished due to the detrimental influence of the cold pool on low-level thermodynamics and questions regarding adequate air mass recovery into the evening. The 10% tornado risk probabilities have been bifurcated to reflect where confidence in the tornado threat is highest. See MCD #764 for additional information on recent observed trends and forecast expectations for southern/central OK. ....Lower MS Valley... An organized, but outflow-dominant, MCS has developed over the past several hours and continues to propagate eastward into southern MS. Latest radar trends and surface observations/analyses suggest that this feature may begin to take on a more southeasterly track through the late afternoon/early evening along a diffuse buoyancy/theta-e gradient into southeast MS. Although the system appears to be outflow dominant, damaging winds remain probable given recent measured wind speeds above 50 mph. ...Moore/Leitman.. 05/11/2023 ..PREV DISCUSSION... /ISSUED 1141 AM CDT Thu May 11 2023/ ....Southern/Central Great Plains... A cluster of storms continues to persist at late morning across south-central Oklahoma, and remain somewhat strong in proximity to the Red River, with other more recent/initial arcing bands of thunderstorm development in a separate regime across southeast Colorado. This is occurring near/ahead of the largely stacked cyclone centered near the Raton Mesa vicinity of northeast New Mexico/southeast Colorado. 12z upper-air analysis features of a zone of stronger mid/high-level winds across the south-central High Plains immediately preceding this cyclone, while winds aloft (especially high level) are otherwise relatively weak across the region. A moist boundary layer is noted across the south-central High Plains, with relatively high PW values and 12+ C 850mb dewpoints observed at both Dodge City and Amarillo per 12z RAOBs, a northwestward extension of the rich low-level moist axis that otherwise extends across the middle part of Texas. The surface cyclone is expected to deepen as it develops toward southwest Kansas today, with the dryline mixing into western Oklahoma and arcing south-southwest into the Edwards Plateau. A north/south-oriented inverted trough/quasi-stationary front will extend north to the western Dakotas. Multiple corridors of increasing severe potential are expected this afternoon. As focused ascent overspreads southeast Colorado into western Kansas, low-topped supercells will become increasingly probable midday to early afternoon within a marginally buoyant environment initially. A smaller area of supercell development may also form in the wake of this activity near the Colorado/Kansas border later in the afternoon and yield a persistent severe threat into early evening. Farther south, the aforementioned early day persistent cluster of storms across south-central Oklahoma casts some uncertainty, particularly in regards to its north, with potential ramifications for areas such as northern Oklahoma/far southern Kansas with the possibility of somewhat more isolated storms. A volatile supercell environment should still evolve to the west of this cluster and ahead of the dryline, especially across southwest into west-central/south-central Oklahoma. A pronounced gradient in MLCAPE is likely by late afternoon to early evening as the most robust boundary-layer heating post-dryline occurs in Texas, while a plume of richer moisture advects north ahead of it. This should support MLCAPE approaching 1500 J/kg near the OK/KS border to around 3500 J/kg along the Red River. While a mid-level jetlet over the southern High Plains will be in an overall weakening state, its favorably timed eastward translation across the dryline should support sustained supercells. Upper-level wind fields will weaken with height and the bulk of hodograph structure will consist of enlarged curvature from 0-3 km. This suggests supercells should tend towards an HP character with a slow-moving cluster type evolution. A moderate increase in low-level flow early this evening could support a strong tornado risk, especially across southern/central Oklahoma with the most intense supercells. A small MCS/embedded supercell cluster will probably persist into eastern Oklahoma before eventually weakening during the overnight. ....ArkLaMiss/Lower Mississippi Valley to Southeast... The environment that potentially produced a couple of tornadoes this morning across northern Louisiana is expected to generally persist eastward across the ArkLaMiss into the afternoon, with a continued potential for mostly brief tornadoes. There will also likely be some increase in damaging wind potential as storm mergers occur and the downstream boundary layer warms and destabilizes. Other more localized/episodic strong to severe storms capable of damaging winds are possible farther east into Alabama, southwest Georgia, and northern Florida, primarily before sunset. $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .