Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Nov 11 2022 12:58:25 ACUS01 KWNS 111258 SWODY1 SPC AC 111256 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0656 AM CST Fri Nov 11 2022 Valid 111300Z - 121200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE CAROLINAS AND VIRGINIA FOR TORNADOES...AND FOR HAIL IN SOUTH TEXAS.... ....SUMMARY... A few tornadoes are possible today over parts of the Carolinas and Virginia. Large hail will be the main severe-weather threat in south Texas. ....Synopsis... A fairly high-amplitude, yet progressive mid/upper-level pattern will persist through the period. A synoptic-scale trough is apparent in moisture-channel imagery from a weak low near the MN Northwest Angle, southwestward across the central High Plains to the Four Corners region. Even as the northern low continues to eject toward James Bay through tonight, a series of shortwave troughs will maintain the synoptic trough and lessen its positive tilt. By 12Z tomorrow, the main trough should reside near an axis from Lake Superior across the upper Mississippi Valley, MO, and the Arklatex region. The associated surface cold front was analyzed at 11Z from a low near ANJ across Lower MI, IN, extreme western KY, the Arklatex region, central TX, and Big Bend National Park. By 00Z, this front should proceed to Lake Erie, WV, eastern TN, western AL, southwestern MS, to near the mid/upper TX Coast and across deep south TX. By 12Z, the front should pick up the remnant low of T.D. Nicole over the northern Mid-Atlantic, while extending across eastern NY, central MD, the western Carolinas,southeastern LA, and the northwestern Gulf. A marine/warm front was analyzed from Nicole's low over GA northeastward across western SC and central/ eastern NC. This boundary should shift northward into VA through the day. ....Carolinas/VA... T.D. Nicole's center is forecast by NHC to turn north-northeastward to the western Carolinas today, before becoming an open-wave trough aloft, then interacting with the surface cold front tonight over the northern Mid/Atlantic/Northeast CONUS. Until that occurs, an expanding area of favorable CAPE/shear parameter space inland will support northward expansion of tornado potential into VA. See SPC tornado watch 569 and related mesoscale discussions for near-term coverage of the tornado threat. Inland/northward shift of the marine/warm front will occur in the area of deep southeasterly flow and low-level warm advection well ahead of the cyclone's center. That, along with upper 60s to low 70s F surface dew points and pockets of sporadic diurnal heating through cloud breaks, will support favorable destabilization in Nicole's middle to far northeastern sector, ahead of a dry slot now moving northeastward over SC. Bands of convection ahead of the dry slot will interact with that air mass. Embedded supercells will become increasingly probable as diurnal instability increases. MLCAPE should reach 500-1000 J/kg -- locally/briefly higher, especially across south-central/southeastern VA and north-central/ northeastern NC. As the system approaches and gradually weakens overall, hodographs should pivot clockwise around the origin and lose some curvature through the day, but remain favorable, with effective SRH generally in the 200-300 J/kg range. Any weakening of the LLJ (and its contribution to hodograph enlargement) related to the weakening of Nicole should be counterbalanced to a substantial extent by the synoptic influence of the approaching mid/upper trough. The tornado threat should diminish tonight as the ejecting remnants of Nicole outrun the favorable low-level instability, and flow in the optimally buoyant air mass veers/weakens. ....South TX... Widely scattered thunderstorms have developed near, then moved behind the surface cold front across parts of the Edwards Plateau and Concho Valley regions, in a regime of elevated frontal lift to LFC and favorable low-level moisture atop the frontal surface. Despite being elevated above a stable boundary layer, 45-55-kt effective-shear magnitudes are expected to persist with this activity as it spreads eastward to east-northeastward across south- central TX through the day, amidst 500-1000 j/kg MUCAPE. This parameter space will support the potential for isolated, marginally severe hail. As the front impinges on a moist axis, extending from the northwestern Gulf northwestward across deep south/south-central TX, additional thunderstorms should develop -- both surface-based along the front and elevated a short distance to its north. Modified soundings and model soundings indicate weak low-level flow preceding the front, but sufficient veering with height to support some hodograph curvature, along with 40-50-kt effective-shear magnitudes, amidst 1500-2500 J/kg peak warm sector MLCAPE. Given the amount of moisture available in the storm-inflow layer, and this supercell- favoring buoyancy/shear parameter space, some significant (2+ inch) hailstones appear possible, and are found in historic sounding analogs. Activity should diminish this evening as the front continues to penetrate through the area, and buoyancy becomes both more elevated and lesser in magnitude. ...Edwards/Smith.. 11/11/2022 $$ = = = 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) .