Administrators NorthGeorgiaWX Posted March 7 Administrators Share Posted March 7 SPC 1300Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0653 AM CST Thu Mar 07 2024 Valid 071300Z - 081200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE SOUTHERN PLAINS... ...SUMMARY... Severe hail and thunderstorm gusts are possible over parts of the southern Plains this afternoon into tonight. ...Synopsis... The mid/upper-level pattern will remain progressive through the period, as a strong shortwave trough exits the northeastern CONUS, and a series of shortwaves traverse an eastward-shifting mean trough across the West. The most important of those shortwaves is evident in moisture-channel imagery over the lower Colorado River Valley region and nearby parts of southern CA. This feature should move eastward across central/southern AZ and adjoining portions of extreme northwestern MX through the period, reaching southern NM and -- at its easternmost part -- the TX/NM border region of the Llano Estacado by 12Z tomorrow. In the foregoing southwest-flow regime aloft, several weak/subtle vorticity lobes should cross portions of the southern Plains States through the period. At the surface, 11Z analysis showed a low over southeastern CO, with wavy and somewhat diffuse warm front across northern parts of the TX Panhandle and OK, to the western Ozarks. The low is expected to migrate across the OK Panhandle to south-central/central KS through the day, with 00Z trailing cold-frontal position across northwestern OK and the northern/central TX Panhandle. By 12Z, the initial low should reach eastern KS or western MO, with cold front to another low near SPS, then across the South Plains to southeastern NM. A dryline should sharpen through the day with continued moist advection to its east. By 00Z, the dryline should extend from the eastern TX Panhandle southward then south-southwestward to northern Coahuila. The cold front will overtake the dryline from north-south across the eastern Panhandle and northwest TX overnight. ...Southern Plains... Isolated, marginally severe hail may occur from elevated thunderstorms now prevalent over portions of the Arklatex to southern Ozarks, eastern OK, and south-central KS, and a zone of steep lapse rates aloft, low-level warm advection and moisture transport above the surface. However, the main severe threat will be later today. Isolated to scattered thunderstorms -- forming along/ahead of the dryline this afternoon and persisting/expanding into the overnight hours -- will be capable of large hail (some potentially 2+ inches in diameter) and occasional damaging to severe gusts. The tornado risk is more sparse and conditional, given a lack of more-robust moisture. A bimodal overall severe-threat distribution still is apparent, with the greatest cumulative convective concentrations likely centered on western OK to southern KS, and that part of west-central to north-central TX in and south of the ongoing convective band. With some reservations, a relative probabilistic minimum will be maintained over the northwest TX region, but with the understanding that any storm forming/sustaining in the environment just east of the dryline still may become a supercell capable of strong-severe gusts and significant hail. Favorable destabilization will develop over the dryline and nearby moist sector by mid/late afternoon, but in different ways from north-south. More sustained/direct insolation and colder air aloft is expected over northern areas where the ongoing high-cloud plume will be less dense, and should exit sooner. In southern areas, shorter duration/weaker magnitude of diabatic heating will be offset to some extent by greater ambient moisture/theta-e. Each process will weaken MLCINH enough to support surface-based convection this afternoon into evening. Aside from the dryline and front, foci for development may include outflow/differential-heating boundaries from morning activity, and a persistent low-level convergence zone already apparent near I-20 from the Big Country into north-central TX. While denser convection training along in that convergence zone may disfavor sustained large-hail potential, embedded supercells are possible, and isolated discrete supercells may offer severe to significant hail farther south. Forecast soundings south of the convergence zone reasonably show rich inflow-layer moisture, strong mid/upper winds and deep shear near the subtropical jet (with 60-75 kt effective-shear magnitudes possible), and long, nearly straight, somewhat hook-shaped hodographs. Splitting storms are possible with severe-hail potential from left- or right-moving supercells. Overnight, as large-scale ascent strengthens ahead of the approaching mid/upper trough, multiple rounds of development are possible, especially in either "slight" risk area. A large-hail and sporadic damaging-wind threat will exist with any such convection. ..Edwards/Jewell.. 03/07/2024 Read more View the full article Quote Link to comment Share on other sites More sharing options...
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