Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Sep 15 2023 12:41:04 ACUS01 KWNS 151240 SWODY1 SPC AC 151239 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0739 AM CDT Fri Sep 15 2023 Valid 151300Z - 161200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SOUTHERN HIGH PLAINS... ....SUMMARY... Scattered large hail, isolated severe wind gusts, and a brief tornado or two are most likely across the southern High Plains, mainly from late afternoon into tonight. ....Southern High Plains to the Middle TX Gulf Coast... At least marginal/isolated severe potential should persist through most of the period within three distinct regimes. The first is with scattered, non-severe thunderstorms progressing east-southeast from the TX Big Country to the Edwards Plateau. While low-level warm advection will subside this morning, short-line segments and clusters may intensify as they impinge on the higher PW air mass characterized by upper 60s to mid 70s surface dew points across central and south TX. While boundary-layer heating will be subdued where stratus lingers, moderate buoyancy should support a primary threat of strong to isolated severe wind gusts from 45-65 mph as convection spreads towards the middle TX coast. In the wake of this initial convective round, pronounced differential diabatic heating will aid in strengthening the baroclinic zone centered on the Permian Basin to Edwards Plateau. Isolated to scattered storms should develop in the late afternoon to early evening within this corridor. While lower-level winds will be weak, favorable mid to upper-level speed shear combined with 2000-2500 J/kg of MLCAPE should support a few supercells with mid-level rotation and a primary threat of large 1-2 inch hail. Some of this activity may congeal into a southeast-moving cluster with modest intensification of low-level southeasterlies during the evening, yielding an isolated wind/hail threat tonight. Finally, a third regime may emanate in multiple waves off the higher terrain of eastern NM during the late afternoon and evening. This activity will be supported by large-scale ascent downstream of a low-amplitude shortwave trough gradually moving east from the Four Corners area. While the boundary layer will not be nearly as warm as the TX Trans-Pecos, the forcing for ascent in conjunction with 25-35 kt 500-mb westerlies will support a few persistent supercells capable of producing occasional large 1-1.75 inch hail. A short-duration severe wind threat may develop tonight over northwest TX as supercells congeal into a southeast-moving cluster. ....South-central MN to northwest WI... Meager buoyancy (MLCAPE of 250-750 J/kg) should develop along a narrow southwest/northeast-oriented corridor between a progressive cold front and a swath of warm-conveyor rain showers. Cooler mid-level temperatures (as sampled by the 12Z INL sounding) attendant to a seasonably strong shortwave trough shifting east from the MB/ON border area should compensate for the limited surface heating ahead of the front. If deep convection can be sustained, the steepening mid-level lapse rates coincident with adequate deep-layer shear will favor a threat of small to marginally severe hail from 0.5-1 inch in the 21-01Z time frame. ...Grams/Marsh.. 09/15/2023 $$ = = = 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) .