Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Mar 31 2023 12:26:54 ACUS01 KWNS 311226 SWODY1 SPC AC 311225 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0725 AM CDT Fri Mar 31 2023 Valid 311300Z - 011200Z ....THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS EASTERN PARTS OF IOWA/MISSOURI/ARKANSAS...ILLINOIS...WESTERN PARTS OF KENTUCKY/TENNESSEE...AND NORTHERN MISSISSIPPI... ....SUMMARY... A severe weather outbreak appears increasingly likely, centered on this afternoon and evening, across a large portion of the Mississippi Valley. At least a few long-track, strong to potentially violent tornadoes are probable, particularly over portions of the Mid-Mississippi Valley to the Mid-South. Swaths of intense damaging wind gusts along with very large hail are expected as well. ....Synopsis... A dangerous severe weather episode appears probable across a large portion of the central states this afternoon into tonight. Primary change with this outlook is to combine the Moderate Risks together given the possibility of long-track, strong to potentially violent tornadoes across a broad region of the MS Valley. ....Midwest and the Mid-MS to OH Valleys... A 992-mb cyclone over eastern NE will deepen through this afternoon as it matures into the Upper MS Valley before occluding this evening. A plume of surface-based buoyancy supported by mid 50s to 60s dew points across the Mid-MO Valley to the southern Great Plains will shift east into the Mid to Lower MS Valleys through the day. Guidance is fairly consistent that initially elevated convection should increase in the Ozarks vicinity by late morning along the eastern gradient of the deeper buoyancy plume as a lobe of low-level ascent spreads northeast downstream of the vigorous central to southern High Plains shortwave trough. While this lead activity will have at least a large hail threat, how the other hazards evolve downstream into the afternoon across the MS River into IL is quite uncertain given large spread in guidance with overall coverage/intensity, along with pronounced differences in how quickly surface-based destabilization occurs to the east. The primary severe evolution remains likely to evolve beginning around 19Z to the southeast of the deep cyclone across central IA and broadening in coverage through the late afternoon along the north/south-oriented cold front arcing southward into eastern MO. Very steep mid-level lapse rates and an elongated mid to upper-level hodograph will initially support a broken band of supercells capable of producing very large hail. As activity rapidly spreads into an increasingly favorable low-level SRH environment in eastern IA and the MS Valley, several tornadoes are expected to form, a few of which could be strong and long-tracked. There should be an adequate gap between the lead and primary rounds of convection to support scattered supercells through at least east-central MO into most of IL into early evening. Within a 3-6 STP environment and the core of the 500-700 mb jets upstream there will be a threat for a couple, long-tracked supercells capable of producing strong to potentially violent tornadoes. All areas from north to south should consolidate into fast-moving line segments with primary threats of tornadoes and significant severe damaging wind swaths over the Midwest and Lower OH Valleys. Later tonight, QLCSs will outpace weakening surface-based instability around the central OH Valley. But the extreme low-level wind fields could support a waning wind/brief tornado threat approaching the central Appalachians. ....Ark-La-Tex to the Lower MS/TN Valleys... Multiple rounds of severe convection are expected to unfold, intensifying this afternoon in AR and Ark-La-Tex, before continuing east across the Lower MS into the TN Valleys through tonight. 60s surface dew points will expand east beneath the southern extent of the extensive EML plume over the central states. This will support a broadening swath of moderate buoyancy characterized by MLCAPE of 1000-2000 J/kg. Strong low-level to deep-layer shear will promote pre-frontal supercells by afternoon. The more intense tornado threat should be during the late afternoon and evening across the Lower MS Valley and Mid-South owing to the peak combination of instability and classic, sickle-shaped hodographs. Strong to potentially violent tornadoes will be possible with a few long-tracked supercells. Upscale growth into a QLCS with embedded supercells appears probable during the late evening and overnight as frontal convergence strengthens. Tornadoes and significant damaging wind swaths will remain possible well into the night across at least the TN Valley, until warm-sector low-level flow becomes more veered towards the end of the period. ...Grams/Goss.. 03/31/2023 $$ = = = 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) .