Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Jun 17 2023 19:57:38 ACUS01 KWNS 171957 SWODY1 SPC AC 171956 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0256 PM CDT Sat Jun 17 2023 Valid 172000Z - 181200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE SOUTHERN HIGH PLAINS...EXTENDING INTO THE SOUTHERN PLAINS AND THE LOWER MISSISSIPPI VALLEY... ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF WESTERN INTO CENTRAL IOWA... ....SUMMARY... Severe thunderstorms, capable of producing damaging gusts, large hail, or tornadoes, are possible over a vast area from Colorado to Florida, and central Texas to the lower Missouri Valley. One or more damaging wind swaths may occur across the southern Plains into the lower Mississippi Valley this evening into tonight. ....20Z update... The enhanced risk was expanded southward and eastward to cover much of northern Texas into the lower MS Valley. An elongated west-to-east corridor of strong to potentially extreme instability is becoming established, from parts of western TX into MS, with the latest mesoanalysis showing up to 5000 J/kg MLCAPE in spots, with nearly the entire southern CONUS overspread by strong mid-level flow and associated 50+ kts of effective bulk shear. At least one or more MCSs are expected to develop from upscale-growing supercells and/or multicellular clusters tonight, and rapidly propagate eastward in the aforementioned favorable environment. Some high resolution guidance shows one MCS traversing central/northern OK, with another MCS moving across northern/central TX into the lower MS Valley. Any of the MCSs that organize will have the potential to produce an extensive swath of damaging gusts, and at least a few instances of 65+ kt gusts are possible. Still, details in MCS evolution, from northern OK, to central TX, remains nebulous, and it is unclear which MCS would dominate and have the potential to become long-lived. As such, within the broader Category 3/Enhanced risk area, there may be a gap in severe potential. Similarly, confidence is also too low to introduce Category 4/Moderate Risk probabilities this outlook. Nonetheless, the existence of a widespread area of favorably overlapping strong shear/CAPE poised to experience scattered severe storms with some upscale growth suggests that broader Enhanced-Risk probabilities are warranted. Significant-severe hail probabilities in the Southeast were extended farther west into southern MS to account for the possibility of 2+ inch diameter hail occurring with ongoing supercells in central/southern MS. Here, MRMS mosaic radar data shows MESH cores already approaching 2 inches in spots. The rest of the outlook remains largely on track, with only slight adjustments made to probabilities to reflect the latest observations or guidance consensus. ...Squitieri.. 06/17/2023 ..PREV DISCUSSION... /ISSUED 1140 AM CDT Sat Jun 17 2023/ ....Southeast CO to Arkansas... Morning water vapor imagery shows a well-defined shortwave trough over southwest CO. This feature will cross the Rockies and begin affecting the High Plains this afternoon, promoting scattered thunderstorms off the high terrain and foothills. Initial supercell storms over southeast CO will be in a region of steep mid-level lapse rates and moderate CAPE, favorable for large hail. As activity moves/builds eastward into southwest KS, the northern TX Panhandle, and northwest OK, it will encounter high CAPE values and increasingly strong low-level winds. Supercells with very large hail, significant wind damage potential, and a few tornadoes may affect this area during the evening. Upscale growth of this cluster of storms into a fast-moving bowing complex remains likely, with activity moving across northern OK into northwest AR tonight. ....North TX... A 50-60 knot westerly mid-level jet max is accompanying the aforementioned shortwave trough over CO. This wind max will move across the TX Panhandle this evening, with enhanced forcing for ascent affecting the dryline over west TX. This will lead to rapid supercell development in a very moist and unstable environment. Very large hail and damaging winds are expected with the stronger cells. Several CAM solutions favor splitting supercells, with left-movers tracking northeastward toward the Red River through the evening with a continued risk of significant severe. Therefore have extended the ENH risk into these areas. ....MS/AL/FL... Morning model guidance shows a subtle shortwave trough currently over west TN tracking southeastward into AL, with an associated 40-50 knot mid-level wind max moving across MS. Strong daytime heating of a very moist boundary layer ahead of these features should result in scattered severe thunderstorm development by mid afternoon over parts of southeast MS, southern AL, and the FL Panhandle. Given the strength of the deep-layer shear, supercell structures capable of large hail and damaging winds are expected. A tornado or two is also possible as the storms approach the coast late this afternoon. Activity should move offshore after dark. ....Western IA... A well-defined remnant MCV is noted this morning over central/eastern NE. Southerly low-level winds ahead of this circulation will maintain near 70F dewpoints over western IA, where strong heating is occurring. This should lead to scattered afternoon thunderstorms. Forecast soundings show sufficient vertical shear for organized multicell or occasional supercell storms capable of hail and damaging winds. Therefore have added a SLGT risk to this region for this afternoon and early evening. $$ = = = 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) .