FXUS63 KLSX 081725 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 1225 PM CDT Wed Jul 8 2026 .KEY MESSAGES... - Seasonably warm temperatures continue today, and scattered showers and thunderstorms are possible, mainly south and east of St. Louis. - More widespread thunderstorms are expected Thursday through Saturday. Some storms could be severe Thursday and Friday afternoon and evening. Additionally, locally heavy rainfall will be possible. && .SHORT TERM... (Through Late Tonight) Issued at 330 AM CDT Wed Jul 8 2026 An upper level low near the confluence of the Mississippi and Ohio Rivers will continue to produce scattered showers and thunderstorms for southeast Missouri and southern Illinois today. The low will drift northeast and weaken, eventually opening into a more progressive wave this evening. This will bring the chance for convection associated with this system to an end for our area. Temperatures today will be a few degrees warmer than Tuesday, except over southeast Missouri and southern Illinois due to more extensive cloud cover and scattered convection associated with the upper low. The next upstream short wave is already producing convection over the northeastern Great Plains into the Upper Midwest. The wave will dig farther into the Midwest today, and then the next behind it will move into the Midwest late tonight, further amplifying the upper flow. Guidance shows another round of convection over eastern Nebraska and Iowa, that moves into northwest Missouri this evening. The convection will continue moving east overnight, and could reach central and northeast Missouri before 12Z Thursday morning, although it should be weak by that time and coverage may be limited. Carney && .LONG TERM... (Thursday through Tuesday) Issued at 330 AM CDT Wed Jul 8 2026 Latest guidance suggests tonight's convection will generate an MCV which will track across the area on Thursday. Additionally, the composite outflow/surface front will drift across northern Missouri into central Illinois during the afternoon and provide a focus for convective development. Temperatures in the low to mid 90s along with dew point temperatures in the low to mid 70s and steepening lapse rates are forecast to produce very unstable conditions with CAPE in excess of 2000 J/Kg. Guidance also shows increasing deep- layer shear up to around 35kts which would support organized convection. Think the most likely scenario is that thunderstorms develop during the afternoon in the vicinity of the MCV/composite cold front over central or northeast Missouri and get organized into a broken line which moves quickly east-southeast. Damaging winds are the most likely threat, though some large hail is also possible given the CAPE profiles in model soundings. Think the severe thunderstorm threat should end during the evening as instability wanes. However, the low level boundary looks like it will remain draped over our area, most likely across the Ozarks, but this is uncertain. Models show a west-southwest low level jet developing during the evening which rides over the boundary producing moderate to strong moisture convergence. Convection is therefore likely to redevelop in the vicinity of the boundary and possibly train along it which would pose a heavy rain threat. Friday's weather continues to depend heavily on convective trends Thursday night. However, current thinking is the boundary will remain over our area, possibly drifting northward through the day as southerly flow increases ahead of another wave. The GFS develops 2000+ J/Kg of CAPE during the afternoon coincident with 30+ kts of shear which will produce another round of thunderstorms Friday afternoon and evening which could be severe.The long wave upper level ridge over the western U.S. begins strengthening and building east Friday night into Saturday. This will eventually push warmer air aloft into the Mid Mississippi Valley and finally cap the low levels. Additionally, the downstream long wave over the eastern U.S. will drag a drier airmass into the Great Lakes and Midwest. This will turn the low level flow over our area to the northeast and finally the surface boundary south. However, it's unclear how quickly this will happen. Guidance PoPs have increased Saturday and Sunday as the models build the ridge eastward more slowly in the latest runs. Additionally the LREF cluster analysis is showing variance in the position and amplitude of the ridge as it strengthens this weekend. This lends a great deal of uncertainty to the forecast for Saturday and Sunday, particularly across the Ozarks where the boundary would likely linger for the longest time. While PoPs now linger into Sunday, Monday and Tuesday continue to look warm and dry under the influence of the upper level ridge. Carney && .AVIATION... (For the 18z TAFs through 18z Thursday Afternoon) Issued at 1220 PM CDT Wed Jul 8 2026 A few isolated showers/weak thunderstorms are expected through early this evening, though mainly across southeast Missouri and southwest Illinois. KSTL/KCPS has ongoing activity nearby, but this may tend to weaken and shift elsewhere over the next hour or two. Dry weather is expected tonight, with rain chances increasing on Thursday, though mainly after 18Z. Gosselin && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX