757 FXUS63 KLSX 250311 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 1011 PM CDT Wed Sep 24 2025 .KEY MESSAGES... - Mainly scattered showers will gradually push southeast tonight and exit the area. - Dry weather is forecast into next week along with daytime temperatures moderating back above normal starting Friday. && .SHORT TERM... (Through Late Thursday Afternoon) Issued at 228 PM CDT Wed Sep 24 2025 GOES-16 water vapor imagery shows an area of vorticity moving toward southwest Missouri early this afternoon. This feature combined with weak low/mid level frontogenesis and a slight uptick in diurnal instability is expected to yield more prevalent shower activity late this afternoon into early this evening. Mainly scattered showers are expected, though there may be brief periods of more widespread showers across parts of east central and southeast Missouri through early this evening. A rumble or two of thunder is also possible, though this should be the exception, not the rule. The more robust showers may be fairly efficient, with precipitable water values still near 1.50" along/south of I-44/I-70 in Missouri/Illinois respectively. The instability that is available, while meager, is also tall/thin looking at soundings. Therefore, while most areas will not see much in the way of additional rainfall (<0.10"), there may be some spots that see as much as 0.50"+ through late this evening. The low-level cyclone quickly pushes off into the Ohio Valley overnight tonight, with any remnant shower activity departing portions of southeast Missouri and southwest Illinois around ~0900 UTC Thursday. Drier, less humid, air will infiltrate the bi-state area behind northerly surface winds. Decreasing clouds are also expected, with at least partial clearing forecast across much of the region. The one exception could be parts of southeast Missouri/southwest Illinois where the clouds may not depart until closer to 1200 UTC. The combination of this partial clearing and light winds should allow for much cooler temperatures tonight compared to last night. Lows are expected to be mainly in the mid to upper 50s, or about 7-10 degrees cooler than last night and near seasonal averages. A quiescent, archetypal early Fall day is on tap for Thursday with light northwest winds and near to just slightly below normal temperatures. Highs mainly in the mid 70s are forecast beneath a partly to mostly cloudy sky. Scattered to broken diurnal stratocumulus clouds are expected to develop by late morning, and these clouds should help limit the temperature rise slightly during the day tomorrow. Gosselin && .LONG TERM... (Thursday Night through Next Wednesday) Issued at 228 PM CDT Wed Sep 24 2025 The synoptic pattern late week into the following week resembles an omega block, with a closed low across the desert southwest and another in the southeastern US. Broad mid/upper level ridging is in between, with the center across the Great Plains. Our region will be between the aforementioned closed low across the southeast and ridging across the Great Plains. At the surface, a broad quasi- stationary area of high pressure is expected to be in place from the Great Lakes southwestward into the mid south. All in all, this looks like a fairly stable pattern with dry weather, light winds, and a mostly clear sky. This is favorable for large swings in temperature day and night. Lows are expected to be mainly in the 50s, with highs moderating into the low to mid 80s. Those temperatures would be very close to normal for lows and about 6-10 degrees above normal for daytime highs as we end the month of September. Gosselin && .AVIATION... (For the 06z TAFs through 06z Thursday Night) Issued at 955 PM CDT Wed Sep 24 2025 Isolated showers have moved south of the terminals, so now expect dry conditions the rest of the period. Fog remains likely at JEF and also now at SUS with MVFR (possible IFR) visibilities between 10-13Z. Dry and VFR conditions are expected thereafter with light winds. Britt && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX