Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Nov 26 2022 12:52:14 ACUS01 KWNS 261252 SWODY1 SPC AC 261250 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0650 AM CST Sat Nov 26 2022 Valid 261300Z - 271200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE NORTH-CENTRAL GULF COAST AND VICINITY... ....SUMMARY... A marginal damaging-wind and tornado threat exists today and tonight over the north-central Gulf Coast and vicinity. ....Synopsis... In mid/upper levels, a positively tilted shortwave trough located over the northwestern CONUS is expected to move southeastward across the Great Basin to the southern Rockies through the period. As this occurs, a strong cyclone -- centered initially near MAF and covering much of the southern Plains and northern MX -- is expected to eject northeastward. By 00Z, the 500-mb low should be near DFW, with trough southward to south-southeastward over parts of east-central/ southeast TX. By 12Z, that low should accelerate northeastward to near MVN, with trough to near the MS/AL border. At the surface, 11Z analysis showed an elongated area of low pressure from the TX Coast between GLS-PSX, north-northwestward to near UTS, and an inverted trough farther inland past the DFW Metroplex. A cold front was drawn from the coastal part of the low southward then south-southwestward across the northwestern Gulf. A marine/warm front -- demarcating low 60s F temperatures and dewpoints inland from mid-70s F temperatures and low/mid-70s dewpoints over the open Gulf -- was drawn from just SE of GLS eastward across southeast TX/southern LA shelf waters. A modified version of this boundary should extend inland over parts of the AL/western FL Panhandle coasts tonight as the surface low wraps through cool inland air toward the mid/upper cyclone center. The more purely unmodified Gulf air south of the boundary may brush across the mouth of the Mississippi River between about 21Z-00Z. ....North-central Gulf Coast and vicinity... A band of scattered thunderstorms now over the northwestern Gulf is expected to move east-northeastward through the day, its northern parts extending progressively further inland while rooted in an elevated unstable layer. Where the line breaks into discrete lightning-producing elements farther south over the open Gulf, well east of BRO and south of BPT, satellite signatures indicate possible supercell(s). Ahead of the line, up until earlier this hour, a persistent, cyclic, right-moving, and possibly tornadic supercell was noted for a few hours in radar imagery offshore from the mid/ upper TX Coast. This storm moved through northwestern parts of the highest-theta-e maritime/tropical air mass, before penetrating the marine frontal zone and weakening. Still, its longevity and organization affirmed a favorable environment along and south of the boundary, and for a short distance to its north. Vertical shear will remain favorable area-wide, amid strengthening mass response to the progressive cyclone. This will contribute to 50-60-kt effective-shear magnitudes and 200-400 J/kg effective SRH. Thermodynamic support appears more tenuous. Considerable uncertainty remains as to how much of the relatively unmodified maritime/tropical air mass can get inland to support more than marginal/conditional severe potential, given that substantial precip/cloud cover is likely to its north. Modified RAOBs and model soundings consistently suggest a deep, nearly saturated overland boundary layer with very low LCL, but also, greatest static stability near the surface. Even where nominally surface-based effective-inflow parcels are present in forecast soundings, at least a shallow layer of stable lapse rates near surface may impede tornado/wind potential. 200-800 J/kg MLCAPE may extend farther inland with eastward extent tonight across southern AL and the western FL Panhandle, as the cyclone and its associated large-scale lift fields shift further inland/poleward of the Gulf Coast. This will occur amidst a strong low-level warm-advection/moisture-transport regime, but also, large areas of precip and messy convective modes that cast doubt on potential for sustained supercells, in an otherwise favorable vertical-shear environment. If just a little more destabilization and/or less-messy potential convective mode becomes evident inland tonight over parts of southern AL and the western FL Panhandle, greater unconditional probabilities may be needed. However, uncertainty remains too great to upgrade that portion of this outlook presently. ...Edwards/Broyles.. 11/26/2022 $$ = = = 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) .