Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Apr 10 2023 12:41:48 ACUS01 KWNS 101241 SWODY1 SPC AC 101240 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0740 AM CDT Mon Apr 10 2023 Valid 101300Z - 111200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTHWEST TEXAS ACROSS CENTRAL OKLAHOMA TO SOUTHEASTERN KANSAS... ....SUMMARY... Isolated severe hail and thunderstorm gusts are possible this afternoon from northwest Texas across central Oklahoma to southeastern Kansas. ....Synopsis... The mid/upper-level pattern over the CONUS will amplify through the period. Ridging will build in the West and move across the Rockies, in advance of a strong trough approaching the coastal Pacific Northwest. Downstream, a series of shortwaves will combine to form a trough today over the Mid-South and southern Plains. The most important of those perturbations is a trough and associated vorticity ribbon now apparent in moisture-channel imagery from eastern MN across eastern NE to central KS. This feature will stretch southward and translate southeastward, in the northern part of the broader field of cyclonic flow attending the height trough just to its south. By 00Z, the height trough should be near a MEM-ACT-FST line, close to a separate vorticity axis, while the stronger vorticity axis extends from northern IL to east-central KS and north-central OK. This will yield DCVA behind the height trough today, though with time tonight, the southern/strongest part of this vorticity ribbon will catch up to the trough. By 12Z tomorrow, the amplifying trough should extend from GA across south TX, with the main vorticity lobe reaching the SAT/DRT corridor. At the surface, 11Z analysis showed a weak surface low along the KS/NE border north of CNK, with trough southwestward across central/ southwestern KS and the northern/western TX Panhandle. A weakening, quasistationary frontal zone was located over the north-central/ west-central Gulf. Optimal maritime/tropical moisture was south of the latter boundary, and will remain well-removed from the outlook area today; however, mid 40s to low 50s F surface dewpoints were analyzed over much of the main body of OK, with mid 50s over central/north-central TX. ....Northwest TX to southeastern KS... Widely scattered to scattered thunderstorms are expected to develop this afternoon near the surface trough, as DCVA/ascent aloft overspread the low-level lift zone, and diurnal heating and boundary-layer convergence combine to remove MLCINH. While activity moves southeastward to southwestward over the outlook area, damaging, isolated severe gusts will be possible, along with at least isolated large hail. A denser corridor of severe potential may become apparent within the outlook area today as mesoscale trends and short-fused progs indicate, but for now, enough storm- evolution uncertainty and model convective dispersion exist to maintain a broad 5% line. Moisture advection will continue through the day from central/north TX, helping to offset the diurnal mixing effects to some extent, and to maintain sufficient boundary-layer moisture for afternoon convection. Progs that bias more aggressive with mixing -- such as RAP and HRRR -- yield lower surface dewpoints, weaker CAPE, and lesser convective coverage, while those with moist biases (e.g., NAM) do the opposite. Expect a well-mixed boundary layer by mid/late afternoon today as the surface trough moves southeastward into the outlook area, likely between the extremes of the models in most areas. Accordingly modified soundings show steep, nearly dry-adiabatic lapse rates underneath about the 600 mb level, with heating, upper 40s to low 50s F dewpoints and cold midlevel air (around -16 C over northwest TX to around -21 C over eastern KS) supporting 800-1200 J/kg MLCAPE -- locally/briefly larger. Flow geometry with respect to the mid/upper trough will result in profiles featuring near-surface southerlies switching near the top of the boundary layer to northwesterlies and northerlies aloft. This leads to nearly straight, north/south-oriented hodographs. In turn, that supports splitting storms, with left movers turning southeastward and right splits moving southwestward. Despite about 180 deg of veering with height, modest deep-layer wind speeds will keep effective-shear magnitudes in the 30-45-kt range. This still will favor some supercell potential, especially with cells moving most deviantly off the hodograph in either direction. After 00Z, deepening stabilization related to nocturnal boundary-layer cooling will reduce buoyancy, with convective coverage and severe potential both decreasing. ...Edwards/Smith.. 04/10/2023 $$ = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .