Subj : DAY1SVR: Day 1 Convective To : All From : Mike Powell Date : Sun Mar 24 2024 08:47:00 ACUS01 KWNS 241246 SWODY1 SPC AC 241244 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0744 AM CDT Sun Mar 24 2024 Valid 241300Z - 251200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE CENTRAL/SOUTHERN PLAINS... ....SUMMARY... Large hail, damaging gusts and a few tornadoes are possible this afternoon and evening over parts of the central/southern Plains. ....Synopsis... The dominant mid/upper-level feature for this period will be a major, synoptic-scale trough progressing eastward across the western CONUS. Moisture-channel imagery indicates a closed cyclone, centered over near-coastal southwestern OR, with troughing south- southeastward roughly along the CA/OR coastline then west of Baja. Ahead of that, a shortwave trough was evident over the lower Colorado River Valley region. The OR low will dissipate today while the basal shortwave trough pivots eastward across southern AZ to eastern NM, reaching near a GCK-CVS axis by 00Z. A new closed 500-mb low should form this evening over the southwestern KS vicinity, temporarily decelerating into erratic/cycloidal motion over the same area until early day-2. At the surface, a low was analyzed near LHX, with warm front across northern KS to near MKC. The low should move little through most of the day, remaining over the High Plains of eastern CO near the KS line as the mid/upper shortwave trough approaches. The warm front should pivot northwestward and merge with an initially separate surface trough over NE. The low should shift eastward over western KS tonight as a wave along a frontogenetic zone. By 12Z, the low should reach north-central KS, with cold front trailing across the TX Panhandle to east-central/northeastern NM, and warm front northeastward to the YKN region then eastward over northern IA. A dryline will become better-defined through the afternoon from a frontal intersection in the GLD-ITR area to southwestern KS, then across western OK to west-central/southwest TX, as moist advection occurs to its east and diurnal heating/mixing to its west. A wind shift and Pacific cold front, preceding the shortwave trough, will move across eastern NM today and west TX this evening, overtaking the dryline tonight. That combined boundary should shift eastward across OK and north/central TX, reaching near a BVO-PRX-SAT line then southwestward into northeastern Coahuila by 12Z tomorrow. ....Central/southern Plains... Isolated to scattered thunderstorms are expected to develop near the dryline this afternoon, some of which should become supercells offering large hail and locally damaging to severe gusts as they move obliquely across the narrow warm/moist sector. A couple tornadoes also are possible as well, especially late afternoon into early evening when a time window of overlap between surface-based inflow and LLJ-maximized hodographs may develop. Tonight, additional thunderstorms are possible as the dryline and Pacific front merge, with isolated potential for all hazards. Ahead of the ejecting shortwave trough, strong height falls, along with left-exit region upper-jet forcing, midlevel DCVA, and accompanying large-scale ascent/cooling, should reach the KS/OK portion of the dryline around midafternoon. Those processes will further reduce already cold mid/upper-level temperatures, especially in areas between I-40 and I-70 before dark. A plume of elevated, non-severe convection/precip should form in moistening, low-level warm advection across parts of western OK into southern KS the next few hours and shift eastward over those states today. Behind that, and beneath the stronger cooling aloft, a narrow sector of diurnally heated moist-sector air should develop -- perhaps only 40-70 nm wide in OK. However, even limited insolation should erode capping considerably over OK and KS while midlevel lapse rates steepen, and moist advection offsets mixing enough to maintain or even increase boundary-layer moisture. Surface dewpoints in the low/mid 50s F already are common from north TX to portions of south-central KS, and should persist or increase somewhat. This will support 500-1200 J/kg MLCAPE in that post-precip/pre-dryline plume. 40-60 kt effective-shear magnitudes are possible over parts of central/ southern KS and western OK, with very large hodographs (effective SRH 300-600 J/kg). As the stronger cooling aloft and frontal forcing extend over increasing moisture tonight, under nearly boundary-parallel mid/upper flow, a line of strong/locally severe convection may form between southern OK and the Edwards Plateau and move eastward. Activity should weaken late overnight to near the end of the period as it encounters a cooling/stabilizing boundary layer. ...Edwards/Grams.. 03/24/2024 $$ --- SBBSecho 3.20-Linux * Origin: ILink: CCO - capitolcityonline.net (454:3/105) .