050 FXUS63 KLSX 041801 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 101 PM CDT Tue Jun 4 2019 .SHORT TERM... (Through Late Tonight) Issued at 340 AM CDT Tue Jun 4 2019 Early this morning, northwest flow aloft prevailed across our region with a broad area of north-south oriented moisture convergence over most of the forecast area as evidenced by low-mid level cloud development with some radar echo in west-central IL and southeast MO. Further west, there was a MCV that has developed straddling the Nebraska-Kansas border helping to continue to drive thunderstorms just ahead of it as they approach northwest MO. A light southeast to south flow was over our region with temperatures mainly in the 60s under mostly cloudy skies. Challenging precipitation forecast the next 24 hours. It appears moisture convergence in association with what will be elevated convection will persist over much of our region through this morning with a low PoP threat for thunderstorms. At some point heading into the afternoon, as convection tends to become more surface or low- level based, the better chances should lean to west of the Mississippi River where the higher surface dewpoints will be, but even then, PoPs look to be low for scattered convection with an isolated severe storm threat. Remember that MCV well to our west early this morning? There is a general consensus on this MCV reaching northeastern MO by late this afternoon and early this evening helping to redevelop a more organized thunderstorm complex that will have the best chance at becoming the main severe storm threat. The thunderstorms that develop here should translate ESE or SE during the evening and early overnight. A dual large hail and damaging wind threat early in its development will probably transition to a mainly damaging wind threat late. With the main frontal boundary still to the north by late tonight, chance PoPs behind this complex still seem justified, especially in light of the presence of a low level jet. Max temperatures should be a bit higher than persistence due to a warmer start to the day and more stout S-SW flow, with readings expected to peak between 80-85. Min temps tonight won't be much higher than dewpoints, with mid to upper 60s most areas. TES .LONG TERM... (Wednesday through Monday) Issued at 340 AM CDT Tue Jun 4 2019 A persistently wet pattern will continue to dominate this period, particularly heading into next weekend. An upper level disturbance interacting with a very moist and unstable environment will be the main weather cause on Wednesday. A surface cold front draped over our region on Thursday will provide the main focus for additional thunderstorm development. Heading into Friday, a slow moving upper LOW heading our way will begin moving even slower thanks to the development of an effective Rex- block as an upper RIDGE amplifies over the north-central CONUS. The latest model guidance does not exit this LOW until next Monday, giving this feature three full days to dominate our weather. Wednesday should be the warmest day with the greatest severe storm risk in this period with the main cold front just beginning to make a push into our area from the north, but convergence along it will be rather weak with the best upper support edging central and southwest IL during the afternoon from the upper level disturbance. There could be other factors that may influence where the best severe storm chances will be but as it stands now, the best combo of upper support, shear, instability and focus will be in southwest IL Wednesday afternoon. Otherwise, QPF for this period still looks to be a widespread 1 to 3 inches with locally higher amounts in slow moving or backbuilding convection. This could cause issues or, at the very least, delays on any drops in river stages into early next week. After widespread max temps Wednesday from the mid 80s to the lower 90s, daytime max temps should slip back to normal for the rest of the period, or mainly in the lower 80s with persistent clouds and rain chances, especially in association with the upper LOW late this week and weekend. TES && .AVIATION... (For the 18z TAFs through 18z Wednesday Afternoon) Issued at 1242 PM CDT Tue Jun 4 2019 Another complex setup for today with TSRA possible during extended periods of time. The first shortwave over eastern KS should bring TSRA to southern portions of the area, which may miss terminals to the south. The threat for storms lingers through much of the night, but enough uncertainty remains that have only mention of VCTS for now. Otherwise, VFR outside of convection with SW to W winds. Tilly && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX