Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jul 18 2023 13:00:57 ACUS01 KWNS 181300 SWODY1 SPC AC 181259 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0759 AM CDT Tue Jul 18 2023 Valid 181300Z - 191200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE MIDDLE MISSISSIPPI VALLEY/LOWER OHIO VALLEY AND TENNESSEE VALLEY... ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHEAST AND NORTHERN PLAINS... ....SUMMARY... Thunderstorms associated with large hail and damaging wind gusts are expected today into tonight from the Lower Missouri Valley southeastward into the Tennessee Valley. Other strong to severe storms are expected in areas across the Northeast States and northern/central Plains. ....Middle/Lower Missouri Valley to Tennessee Valley... Concern has increased for a corridor of severe weather today into tonight across Missouri southeastward toward the Lower Ohio Valley and Tennessee Valley. Strong elevated thunderstorms are currently ongoing this from southeast Nebraska into central Missouri, with some MCV-related influences apparent. This activity will continue to spread southeastward and likely intensify, potentially as early as late morning, but especially this afternoon as storms develop into an increasingly unstable air mass along/south of a regional front. In the presence of strong instability and seasonally strong northwesterly flow aloft, one or more well-organized clusters are likely to evolve later this afternoon into evening, with a damaging wind/some hail risk continuing into the Tennessee Valley. Additionally, another round of elevated thunderstorms are expected to develop late tonight along the convectively modulated northwest/southeast-oriented frontal zone across Missouri and areas near the confluence of the Ohio/Mississippi Rivers. This could include elevated supercells with a threat for large hail given strong elevated instability and strong deep layer shear. Eventually, some upscale growth will be possible and a severe wind threat could materialize pending late-night MCS development. ....Northern Plains... A combination of low-level moisture advection and surface heating will lead to moderate to strong instability across central North Dakota and South Dakota by this afternoon. This instability, combined with convergence from a sharpening cold front and an approaching mid-level shortwave trough, should be sufficient for strong/severe thunderstorm development near the front this afternoon. Mid-level winds of 45-55 kt will contribute to supercell-favorable wind profiles and related risk for large hail, some potentially 2+ inches in diameter. ....Northeast/Mid-Atlantic States and New England... Steady height falls will continue to overspread the region, influenced by moderately strong cyclonic flow aloft via the northern Ontario/Quebec upper-level trough. While locally heavy rainfall may be the primary concern across much of the region, relatively long/semi-straight hodographs and diurnally maximized instability will support semi-organized/sustained storms capable of wet microbursts and isolated wind damage. Some hail could also occur. ....Central High Plains... A few thunderstorms are possible late this afternoon as low-level upslope flow evolves, with increasing low-level moisture to the north of the surface cyclone. The favorable environment may be relatively short-lived given the late-day increase in moisture, but a favorable environment for a few severe thunderstorms may develop with 2000+ J/kg MLCAPE and supercell wind profiles. ....Great Basin... A deeply mixed boundary layer is expected today across the Great Basin with ample instability for scattered thunderstorms across much of the region. A belt of stronger mid-level winds around 30 kt will exist from east-central Nevada into north-central Utah. This may support some storm organization with the potential for isolated severe-caliber wind gusts given the well-mixed sub-cloud layer. ....Southern Arizona... Thunderstorms are expected to develop over the Rim/White Mountains and higher terrain of southeast Arizona this afternoon. The region will be nearly coincident with the upper high. While mid-level steering flow will be weak, a westerly component of near-surface winds will likely support propagation into the desert floor, particularly across southeast Arizona within a relatively moist but hot/deeply mixed boundary layer. Some strong, potentially severe-caliber, outflow winds may occur late this afternoon/early evening. ...Guyer/Kerr.. 07/18/2023 $$ = = = 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) .