Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Dec 13 2022 19:58:37 ACUS01 KWNS 131958 SWODY1 SPC AC 131956 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0156 PM CST Tue Dec 13 2022 Valid 132000Z - 141200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF EAST TEXAS...LOUISIANA...AND SOUTHERN/CENTRAL MISSISSIPPI... ....SUMMARY... Tornadoes (some strong), scattered damaging winds, and sporadic large hail will remain possible this afternoon/evening and overnight from parts of east Texas into Louisiana and southern/central Mississippi. ....20Z Update... Primary change with this update was to trim severe probabilities behind an ongoing broken line of convection extending from parts of east TX into western AR. The potential for a few strong tornadoes remains evident this afternoon and evening from portions of east TX into LA. A very impressive kinematic profile exists based on recent VWPs from KSHV, with 0-1 km SRH over 400 m2/s2. Any supercell that can be sustained in this strongly sheared environment will be capable of producing a tornado. The main uncertainty continues to be whether sufficient instability will exist with eastward extent across northern/central LA this evening to support a substantial tornado threat. Convective mode and evolution also remain somewhat uncertain, but deep-layer shear is clearly strong enough for supercells. The threat for tornadoes, some of which could be strong, will likely continue this evening into the overnight hours into MS and southeastern LA, as low-level shear should remain quite strong in association with a 35-45 kt southerly low-level jet. ...Gleason.. 12/13/2022 ..PREV DISCUSSION... /ISSUED 1029 AM CST Tue Dec 13 2022/ ....Synopsis... A 100 knot mid-level jet across West Texas this morning will advance across the Plains and into the Upper Midwest by tonight. At the surface, an area of low pressure will slowly move from northwest Kansas to eastern Nebraska. An occluded front extends from the surface low across northwest Kansas to southeast Oklahoma where it intersects with a warm front. Currently this warm front is oriented more north/south, extending to near Lake Charles, Louisiana, but is expected to orient more northwest/southeast through the day as low-level winds veer. As this occurs, mid to potentially upper 60s dewpoints will advance inland and lead to a more broad warm sector through the day. ....Eastern Texas across central/northern Louisiana... A combination of QLCS and supercell type tornadic circulations have occurred within and slightly ahead of a squall line across southern Oklahoma and north Texas this morning. The northern extent of the threat across southeast Oklahoma has started to wane as the line is being cut off from the better low-level moisture. However, the threat is expected to persist through the morning and early afternoon across northeast Texas where mid 60s dewpoints are already in place and expected to increase through the day amid strengthening low-level flow. The greatest threat will be this evening into the overnight hours from east Texas across Louisiana and into western Mississippi. There is considerable agreement among 12Z CAM guidance for supercells to develop within the uncapped warm sector across east Texas and central Louisiana this afternoon and evening. Most forecast soundings show high temperatures in the 72-73F range at KPOE late this afternoon. However, given at least some broken nature to the upstream cloudcover, would expect temperatures in the mid 70s to be more common. This would lead to MLCAPE in excess of 1500 J/kg south of the warm front. This instability paired with strong low-level shear would pose a threat for strong tornadoes through the afternoon and evening across central Louisiana. ....Eastern/southeastern Louisiana into southwest Mississippi... Late tonight, the cold front is expected to slow across eastern Louisiana with the majority of convection becoming pre-frontal. Despite unfavorable diurnal timing, MLCAPE of 1000 to 1500 is expected to persist as cooling temperatures aloft continue to overspread low-level moisture advection off of the Gulf of Mexico. In addition, an uptick in warm sector storm coverage may occur as some guidance indicates a weak meso-low to develop off the Gulf of Mexico. Favorable hodographs are expected to persist through the overnight period and therefore a tornado threat should continue. An upgrade to higher probabilities was considered due to the expectation for warm sector supercells to develop amid favorable hodographs and a STP of 3-4. However, slightly stronger instability would have been preferred to initiate an upgrade. $$ = = = 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) .