189 FXUS63 KLSX 231119 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 619 AM CDT Thu May 23 2019 .SHORT TERM... (Through Late Friday Afternoon) Issued at 417 AM CDT Thu May 23 2019 Ongoing broken line of strong to severe thunderstorms from Vandalia, IL through STL Metro to near Springfield, MO continues to slowly push southeastward, where the effective surface boundary currently is. It is on portions of this leading edge where the Flash Flood threat, if there is one, has also shifted. Some additional non-severe thunderstorm development continues to lag further northwest through central MO thanks to WAA aloft. Temperatures were in the 70s ahead of the effective surface boundary, and have fallen off into the 60s and even 50s behind it and the slightly lagging synoptic cold front. There is enough dynamic and thermodynamic support for severe storm threat to persist a couple hours after sunrise as it pushes more into southern IL and southern MO. This may mandate a temporal extension of WW215 as a result. Otherwise, overall coverage of storms looks to decrease heading later into the day and into tonight as it gradually shifts back northward into northern MO and central IL late tonight, with the effective boundary shifting into more capped air as the upper RIDGE attempts to build back into our area. The upper RIDGE looks to have one good day where it is well established, and should result in a mostly dry forecast for Friday but will also result in a hot day as well, with max temps well into the 80s all locations with low 90s possible in the STL metro area. The strength of this RIDGE after Friday looks wobbly to the point where convective development just to the northwest of our region looks likely and as/if this persists, will likely shift the main activity back into our region again anyway. If this happens, this is also probably to be accompanied with a severe storm and excessive rainfall threat building in from northeast MO and possibly for areas further southeast. TES .LONG TERM... (Friday Night through Wednesday) Issued at 417 AM CDT Thu May 23 2019 This pattern looks set to then continue well into next week with rain chances shifting northwestward for a time if the RIDGE can regain dominance and then back into our area as it weakens. There is low confidence on any one particular day being dry or wet and being this is May going into June, the two wettest months climatologically, the likelier solution is on the wetter weather until a higher confidence pattern emerges. When the RIDGE is more dominant, temperatures will surge well into the 80s and into the low 90s in spots, whereas wetter weather will tend to keep them in the lower 80s or even 70s. TES && .AVIATION... (For the 12z TAFs through 12z Friday Morning) Issued at 609 AM CDT Thu May 23 2019 The effective surface boundary continues to slowly push south. As this boundary lifts north today, a threat for isolated storms will continue across the region through the afternoon. With low chance of these storms impacting terminals, will leave out of the TAF for now. Will need to monitor for additional thunderstorm threat late tonight, possibly impacting KCOU and KUIN. Tilly && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX