Subj : DAY1SVR: Enhanced Risk SE To : All From : Dumas Walker Date : Mon Mar 25 2024 08:41:00 ACUS01 KWNS 251245 SWODY1 SPC AC 251243 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0743 AM CDT Mon Mar 25 2024 Valid 251300Z - 261200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS IN PARTS OF EASTERN LOUISIANA AND SOUTHEASTERN ARKANSAS TO EASTERN MISSISSIPPI... ....SUMMARY... Tornadoes and damaging thunderstorm gusts are possible today through tonight from east Texas to Alabama. ....Synopsis... In mid/upper levels, a well-developed synoptic trough extends from a cyclone over the central Plains southwestward across far west TX to northwestern mainland MX and central Baja. A series of shortwaves behind the leading/synoptic trough will help to maintain larger- scale cyclonic flow over much of the western/central CONUS and northern MX through the period. However, the 500-mb cyclone should move erratically across KS today into this evening, reaching parts of northwestern MO, IA and southern MN by 12Z tomorrow. To its east and south, a broad, strong fetch of cyclonically curving, roughly southwesterly flow aloft will shift eastward from the Southern Plains across the lower Mississippi, Tennessee and lower Ohio Valleys. At the surface, 11Z analysis showed a low near CNK, with Pacific/ leading cold front having overtaken the dryline and drawn through north-central/south-central TX to easternmost Coahuila. A polar front was drawn from the low across northwestern OK, the southern TX Panhandle and east-central NM. The low should move to west-central IA by 00Z, with leading front reaching eastern parts of MO/AR, northern LA, extreme southeast TX, and the northwestern Gulf. By then, the polar front should extend southward over easternmost parts of KS/OK to north-central TX, the northern Permian Basin region of TX, and southeastern NM. By 12Z, the low should reach northwestern WI, with the fronts essentially merged southward to western KY, and the leading boundary from there across southeastern parts of MS/LA. ....East TX to AL... A swath of precip and embedded convection -- including widely scattered thunderstorms -- is apparent along and ahead of the Pacific front, from portions of central TX into the Ozarks. Much of this activity has exhibited a disorganized, anafrontal character for several hours, as the leading boundary continues to progress slightly rightward of storm motion. Overall severe potential should remain marginal over the next few hours as that general character persists. However, severe potential should ramp up from midday onward across the outlook area amid favorable/strengthening ambient deep shear. Two processes will contribute to increased surface-based convective/severe potential along this boundary from midday into tonight: 1. Some slowing of the boundary and decrease in anafrontal tendencies as it crosses the lower Mississippi River/Delta region, and 2. The foregoing warm sector becomes substantially more buoyant through a combination of warm advection, moist advection and diabatic heating of the boundary layer -- especially from a few counties north of I-20 southward. Forecast soundings reasonably depict a northward-narrowing, triangular wedge of 500-1500 MLCAPE shifting eastward over the region ahead of the main convective line. While much more uncertain, discrete supercell development may occur off the southern/southeastern part of the line, given progged decrease in MLCINH in the free warm sector. The geometry of the height gradient aloft -- around the southern rim of the ejecting cyclone and associated/trailing shortwave trough -- still will maintain a strongly parallel flow component to the primary band of convective forcing, helping to maintain quasi-linear mode. However, given the strength of the deep shear (effective- shear magnitudes of 55-65 kt), and of the low-level shear/hodographs (effective SRH of 250-500 J/kg), the line will encounter in and near the "enhanced" area, tornadoes are probable from associated LEWP/bow formations and embedded mesovortices, as well as any supercells that can mature enough before/during QLCS merger. The parameter space will support significant (EF2+ damage potential) tornadoes as well, though local storm mode/duration will strongly regulate that threat. The QLCS gradually will outpace the favorable inflow-layer thermodynamic regime from north-south, as it moves eastward into AL overnight, but with southern parts still offering a severe threat. ....Lower Missouri Valley region... Widely scattered to scattered thunderstorms should form this afternoon near the surface low and polar front. Isolated, marginally severe hail or gusts may be noted, and a tornado is possible. The airmass between the leading and polar fronts will remain somewhat moist, with surface dewpoints in the 50s F over much of the region. Diabatic heating and warm advection will contribute some low-level destabilization, though its duration and strength will be limited within a narrow corridor northwest of the cloud/precip shield from the aforementioned main convective band. However, large-scale lift preceding the ejecting mid/upper-level low and trough should lead to cold air aloft (e.g., 500-mb temperatures around -19 to -22 deg C), steepening low/middle-level lapse rates and decreasing MLCINH through much of the afternoon. This should support MLCAPE around 500 J/kg, with strong deep/speed shear and potential for vorticity-rich low-level boundaries to augment shear/hodographs locally. Convection should weaken soon after dark. ...Edwards/Wendt.. 03/25/2024 $$ --- SBBSecho 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (21:1/175) .