Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Dec 27 2024 17:33:51 ACUS02 KWNS 271732 SWODY2 SPC AC 271731 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1131 AM CST Fri Dec 27 2024 Valid 281200Z - 291200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF EAST TEXAS...THE LOWER MISSISSIPPI RIVER VALLEY INTO THE TENNESSEE VALLEY... ....SUMMARY... A regional outbreak of severe storms, with large hail, damaging winds, and strong tornadoes is possible Saturday into Saturday night, from East Texas, across the Lower Mississippi Valley, into parts of the Tennessee Valley. ....Synopsis... Mid-level flow is expected to rapidly amplify over the southern CONUS Saturday, as several southern stream perturbations intensify as they move near the Gulf Coast. A prominent shortwave trough, initial located across the southern OH Valley, will quickly eject northward as a second stronger shortwave approaches from the southern Plains vicinity. A roughly east-west oriented warm front will quickly move inland overnight Friday and into early Saturday in response to increased mid-level height falls and a deepening surface low near the Red River. This will allow for robust moisture return, with upper 60s to low 70s F dewpoints likely across the lower MS Valley by daybreak. While clouds and precipitation from inland moisture advection may complicate destabilization to some degree, sufficient buoyancy is expected to support numerous strong to severe storms with all hazards possible from East TX and the lower MS valley, into the TN valley from Saturday morning into early Sunday. ....East TX, Lower MS Valley... As the mid-level flow pattern quickly amplifies Saturday, the prominent shortwave trough and a subtle lead wave over the southern plains should rapidly strengthen, taking on neutral to slightly negative tilts by 00z Sunday. As this occurs, increasingly strong diffluent flow aloft will overspread East Texas toward the ArkLaMiss vicinity, where middle 60s F surface dewpoints will become more common. Steepening low/mid-level lapse rates and diurnal heating should allow for moderate destabilization, despite some lingering clouds and isolated elevated storms. Deeper convection is expected to develop early in the period (11-14z) as ascent from the embedded perturbation and main trough move over a pre-frontal confluence axis across East TX/Western LA. A second round of robust convection may also develop across eastern TX later in the afternoon as a Pacific front associated with the surface low over North TX impinges on the warm sector from the west. A mix of semi-discrete supercells and linearly organized bowing segments are expected with sufficient buoyancy/deep-layer shear overlap for storm organization. An initial risk for large hail, especially where low-level flow is somewhat veered, should transition to a risk for damaging winds and tornadoes as 0-1 km SRH increases to 150-300 m2/s2 into mid/late Saturday afternoon with a 35+ kt 850 mb low-level jet. Convection should quickly spread northeast into the lower MS Valley, peaking in intensity through the afternoon and early evening hours. Coincident with an increase in the low-level jet to 45-65 kt and intensifying surface pressure falls, low-level hodographs will expand with 0-1 km SRH of 300-400 m2/s2 likely. This will support the potential for strong tornadoes with any established suppercellular elements. ....Tennessee Valley and Cumberland Plateau... As the upper trough continues to amplify through the day, the warm front will gradually lift north into the southern TN valley by early afternoon. A broad area of cloud cover and perhaps light stratiform precipitation is expected in the presence of strong isentropic ascent along the advancing warm front. This remains the primary uncertainty regarding the northern/eastern extent of the surface-based severe risk later Saturday afternoon into Saturday night. While buoyancy/destabilization may be muted, the intensifying upper trough and surface low will favor very strong low and mid-level wind fields supportive of storm organization into Saturday evening and early Sunday. With very large low-level hodographs (0-1 km SRH 300-500 m2/s2) weakly buoyant near-surface based parcels will still allow for some tornado and or damaging wind risk into the overnight hours, especially with any established supercell or bowing structures across parts of AL, TN and western GA. ...Lyons.. 12/27/2024 $$ = = = 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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .