Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jan 22 2023 12:48:51 ACUS01 KWNS 221248 SWODY1 SPC AC 221247 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0647 AM CST Sun Jan 22 2023 Valid 221300Z - 231200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE NORTHEASTERN GULF COAST ACROSS SOUTHERN GEORGIA AND SOUTHERN SOUTH CAROLINA... ....SUMMARY... A few marginally severe thunderstorms are possible today over a corridor from the northeastern Gulf Coast across southern Georgia and southern South Carolina. A tornado or two and isolated damaging to severe gusts are possible. ....Synopsis... Another day of progressive, relatively high-amplitude shortwave to synoptic-scale activity is expected in mid/upper levels. A well- defined synoptic trough -- initially located from the upper Mississippi Valley southwestward across OK to north-central MX -- contains several lengthy voracity banners from absorption of prior shortwave perturbations. By 00Z, this through should shift east-northeastward to near a GRR-SPI-TXK-CLL axis, losing some amplitude while maintaining a 500-mb low over IN. By 12Z, the trough is expected to reach the lower Great Lakes, upper Ohio Valley, and southern Appalachians. Upstream, a closed mid/upper- level cyclone is evident in moisture-channel imagery over ID. This vortex should enlarge, intensify, and dig southward across the eastern Great Basin through the period, with its center reaching western AZ by 12Z tomorrow. At the surface, 11Z analysis showed a broad area of low pressure over much of MS/AL and the western FL Panhandle, with a weak low between PNS-GZH. The low should move northeastward and weaken through the afternoon, with another low forming by 00Z over northeastern NC. The marine/warm front should move northeastward and inland, becoming more diffuse, and shallow in slope throughout the low levels amid strong warm advection. By 00Z, the cold front should trail from the NC low southwestward across eastern SC, southern GA, and the FL Gulf coastal bend, to the central Gulf. By 12Z, the low should reach the ACK area, with cold front southwestward across Atlantic waters to central FL, then to the southern Gulf. ....Southeast... A few rounds of scattered thunderstorms are expected to move across the outlook area through this evening, along and ahead of the cold front, in an environment of favorable deep shear but generally weak instability. The most intense cells may offer damaging gusts to near severe limits, as well as a brief tornado threat. Messy convective mode and lack of stronger buoyancy should keep the severe risk isolated. Variably organized bands of convection are evident at this time from southwestern GA southwestward across the central FL Panhandle and over the adjoining Gulf. This activity, as well as potential warm-sector development over southern GA and northern FL through the day, should result in increasing prefrontal convective coverage. Meanwhile, a dominant band of near-frontal thunderstorms should develop by early/mid afternoon across the northeastern Gulf as the front accelerates into the area and strengthens somewhat. This activity may build northeastward across GA/SC. The frontal band should reach the nearby Atlantic Coast this evening, while weakening over parts of northern FL. Cloud cover and precip will limit diurnal destabilization, while mean midlevel lapse rates should remain only slightly greater than moist adiabatic over the region. Still, low-level theta-e advection should gradually erode/destabilize the stable boundary layer sampled by the 12Z TLH sounding. With time into the afternoon, this process will render surface-based effective-inflow parcels over much of the outlook area, as the broader convective regime shifts across. Peak MLCAPE may range from around 1000 J/kg over the eastern FL Panhandle and coastal bend/north FL region to 300-800 J/kg over the SC Lowcountry. Meanwhile, some veering of boundary-layer flow is expected toward a nearly unidirectional deep-layer wind profile, suggesting quasi-linear segments will be the dominant type of convection. Still, favorable speed shear should contribute to effective-shear magnitudes in the 35-50-kt range, supporting potential for bow/LEWP activity and transient/embedded mesocirculations. ...Edwards/Dean.. 01/22/2023 $$ = = = 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) .