Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Sep 20 2023 05:56:33 ACUS02 KWNS 200556 SWODY2 SPC AC 200555 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1255 AM CDT Wed Sep 20 2023 Valid 211200Z - 221200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE CENTRAL AND SOUTHERN HIGH PLAINS...SOUTHERN PLAINS...AND THE ARKLATEX... ....SUMMARY... At least isolated strong to severe thunderstorms are possible across portions of the Plains toward the Arklatex Thursday into Thursday night. ....Synopsis... A broad upper-level trough will become established across the Interior West tomorrow/Thursday. Multiple mid-level perturbations will pivot around the upper trough, with at least one lead impulse ejecting into the Plains states by Thursday afternoon. A surface low will intensify over the central High Plains in response to the approach of this lead impulse, supporting backed surface winds and northwestward low-level moisture advection. Mid-level cooling atop returning low-level moisture will foster increasing instability across the Plains states, in tandem with some deep-layer ascent. Scattered strong to severe storms may manifest in this regime from the central/southern High Plains to the Arklatex. ....Central High Plains to the central Plains... Increased low-level convergence should occur during the afternoon due to surface low development and associated upslope/moistening low-level flow across the central High Plains. Upper 50s to near 60 F surface dewpoints beneath 8 C/km mid-level lapse rates will support 2000-3000 J/kg SBCAPE by afternoon peak heating. At the same time, southeasterly surface winds will be overspread by a 25-35 kt southwesterly 850 mb jet and westerly 500 mb winds at similar magnitudes, resulting in curved and elongated hodographs with 35-45 kts of effective bulk shear. Some convective inhibition will be present through the afternoon, and when considering modest forcing for ascent, widespread severe storm coverage becomes questionable. Nonetheless, at least some diurnal development is likely in the form of isolated supercells capable of severe hail and wind. Some upscale growth into an MCS is possible along the low-level jet terminus in NE Thursday night, with a couple of severe gusts possible. Greater severe probabilities may be needed in future outlooks if denser storm coverage becomes apparent. ....Southern Plains... The ejection of a lead mid-level impulse across the southern Plains will support strengthening west-southwesterly low-level flow and associated warm-air advection during the late morning or early afternoon time frame. Some of the latest high-resolution guidance depicts the development of scattered strong thunderstorms, with upscale growth into an MCS possible somewhere along the Red River. Should this development occur, a couple instances of severe hail will be possible given steep mid-level lapse rates, though relatively dry air in the low to mid-levels (as shown in some forecast soundings) may also encourage a couple of severe gusts. ....Southern High Plains... Modest surface heating will encourage surface temperatures to warm well into the 80s F. With low 50s F surface dewpoints, this will support the development of a deep, well-mixed boundary layer. Lapse rates should be steep through the troposphere. Furthermore, a belt of stronger mid-level flow will overspread the southern High Plains with the ejection of a lead mid-level impulse, resulting in elongated hodographs. Scattered, fast-moving multicellular thunderstorms should develop during the afternoon with an attendant isolated severe-gust threat. ...Squitieri.. 09/20/2023 $$ = = = 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) .