Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Jul 06 2023 17:29:51 ACUS02 KWNS 061729 SWODY2 SPC AC 061728 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Thu Jul 06 2023 Valid 071200Z - 081200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE CENTRAL AND SOUTHERN HIGH PLAINS INTO THE SOUTHERN PLAINS... ....SUMMARY... Severe wind and hail producing storms are expected across the central and southern High Plains into the southern Plains tomorrow/Friday. A couple of damaging gusts are also possible across the Upper Hudson Valley. ....Synopsis... A pronounced mid-level trough will traverse the central CONUS while a secondary mid-level perturbation crosses the southern Rockies and ejects into the southern Plains tomorrow/Friday. Meanwhile, the approach of the mid-level trough over the Midwest will also support weak surface troughing along and to the lee of the central and northern Appalachians during the afternoon hours. Multiple rounds of organized strong to severe storm potential should occur across the central U.S., including at the start of the period. The most robust severe storm development should occur across the southern Plains with the ejection of the mid-level perturbation, with all severe hazards possible. Scattered strong thunderstorm development may also occur across the northeast in tandem with the weak surface lee trough. ....Southern High Plains into the southern Plains... One or more loosely organized MCSs will likely be in progress over portions of the southern Plains at the start of the period (12Z Friday morning), perhaps accompanied by a marginal severe wind threat. With time, as the low-level jet weakens, the MCSs should dissipate through the late morning/early afternoon hours. Similar to Day 1, residual showers and cloud cover will gradually clear, allowing for surface temperatures to rise over 90 F in the TX Panhandle, to over 80F points north. These temperatures, along with surface dewpoints into the low to mid 60s F, overspread by 8.5+ C/km mid-level lapse rates, will support strong buoyancy (i.e. 3000+ J/kg SBCAPE), especially in the northern TX Panhandle. By late afternoon into early evening, a 20-30 kt southwesterly low-level jet, overspread by 40-50 kts of 500 mb westerly flow, will support 40-50 kts of effective bulk shear, characterized by hodographs with some low-level curvature and mid-level elongation. Questions remain regarding initial storm coverage (especially north of the TX Panhandle) due to capping. However, at least isolated supercells should initiate by late afternoon with a large hail threat. A few 2+ inch stones and a couple of tornadoes cannot be ruled out. Later in the evening, upscale growth into a severe-wind producing MCS is possible. The overall coverage and severity of this MCS is predicated on the number and intensity of initial merging supercells. The isolated nature of the initial supercells and lack of higher confidence in robust MCS development precludes greater severe wind/hail coverage probabilities this outlook. ....Northern Plains... Behind the progressing mid-level trough, a weak cold front will sag southward across the northern Plains during the day. Insolation and boundary-layer mixing, overspread by 7 C/km mid-level lapse rates, will foster 1000-2000 J/kg SBCAPE by afternoon peak heating. Deep-layer shear will not be overly strong (i.e. generally under 30 kts of effective bulk shear). Nonetheless, enough hodograph curvature/elongation may exist to support stronger pulse-cellular storms or loosely organized multicell clusters with an isolated severe gust threat along with some small hail. ....Midwest... Thunderstorm clusters, potentially in the form of loosely organized MCSs, may be ongoing at the start of the period across eastern portions of the central Plains toward the central MS Valley region. These storms will be supported at the terminus of a 30+ kt low-level jet, accompanied by a marginal severe hail/wind threat. Airmass modification behind the initial storms will be modest and gradual due to lingering clouds and precipitation, limiting instability later during the afternoon. Nonetheless, the passage of the upper trough atop a southward-sagging baroclinic zone may serve as a focus for some renewed convective development by late afternoon. Given modest instability (relatively poor mid-level lapse rates fostering 500-1500 J/kg MUCAPE - most of which may be elevated), later severe potential should not be widespread. Nonetheless, given elongated hodographs (and 40-50 kts of effective bulk/speed shear) multicellular storms (and perhaps a brief, transient supercell) are possible by late afternoon, with a couple of severe gusts/large hail stones possible. ....Upper Hudson Valley... Adequate surface heating of a moist boundary layer will support surface temperatures warming well into the 70s F amid mid to upper 60s F dewpoints, resulting in MLCAPE over 1000 J/kg (perhaps approaching 2000 J/kg in spots). The combination of weak ascent associated with the surface lee trough and insolation will support the initiation of scattered thunderstorms by early afternoon. Deep-layer shear should not be overly strong, though point forecast soundings suggest modest hodograph elongation, especially closer to the international border. As such, a few longer lived multicells and pulse single-cells may organize, capable of supporting wet downbursts, a couple of which may approach severe limits. As such, damaging gusts may accompany the stronger storms, warranting the introduction of Category 1/Marginal risk-driven wind probabilities. ...Squitieri.. 07/06/2023 $$ = = = 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) .