FXUS63 KLSX 150013 AFDLSX Area Forecast Discussion National Weather Service St Louis MO 713 PM CDT Wed Oct 14 2026 .KEY MESSAGES... - Widespread showers and thunderstorms are expected late tonight into Thursday morning. - Additional, potential shower and thunderstorm development during the afternoon and evening could include a severe thunderstorm or two with isolated damaging winds and, conditionally, a brief tornado. - Behind a cold front Thursday night, temperatures will become much cooler and seasonable, with a warming trend early next week. && .SHORT TERM /THROUGH THURSDAY/... Issued at 203 PM CDT Wed Oct 14 2026 Waves of widespread showers and thunderstorms have shifted much further southward into southern MO and AR this afternoon--most of which will remain to the south/southwest of the CWA through this evening aside from a few light showers or sprinkles. The effective front has also been pushed south of the CWA by this activity, leading to a much cooler day beneath considerable cloud cover, but high temperatures in the upper 60s and 70s F are still above average for mid-October. Not only that, but dewpoints are still running above the 90th climatological percentile, leading to an atypical mugginess. In response to the northeastward ejection of an upper-level trough currently over the Four Corners Region, the aforementioned front will advance northward tonight into Thursday as surface cyclogenesis ensues near the NM-TX border. A wing of associated low to mid-level isentropic ascent/WAA will drive a broad area of showers and thunderstorms that lifts northeastward through the CWA late tonight into Thursday morning. With thunderstorms anticipated to be quite progressive, flash flooding is unlikely but brief high rainfall rates are anticipated from near-record breaking PW around 2". The majority of morning showers and thunderstorms will continue to lift northward and end from south to north Thursday morning ahead of a surface cyclone tracking northeastward across MO through the day. There is variability in model guidance on how deep/mature the cyclone gets and how far the warm front lifts and warm sector expands across the CWA. These details along with the amount of lingering cloud cover will have ramifications on temperatures, instability, and more importantly how thunderstorms redevelop during the afternoon. With 40 to 50 kt of deep-layer wind shear, there is a concern for severe thunderstorms if enough instability becomes available. Upward trends in successive runs of the HREF and REFS SBCAPE is slowly increasing confidence in sufficient instability with the interquartile range now around 1000 to nearly 2000 J/kg in the warm sector. Timing, coverage, and location of thunderstorms is not clear, but the most favored location would be near east-central MO into IL where convergence is greater near the surface cyclone. Surface winds are projected to be veering in the warm sector, but backed winds near the warm front just ahead of the cyclone could increase low-level hodograph curvature enough for a brief tornado. Otherwise, isolated damaging winds are the greatest threat in a mixed mode of QLCS segments and supercells, with potential additional development along the trailing cold front southward through the evening. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... Issued at 203 PM CDT Wed Oct 14 2026 The cold front will progress eastward Thursday evening into overnight, but some showers could linger behind the front well into into the night along/east of I-44/I-55. The primary impact of the front will be the onset of strong low-level CAA that persists through the day Friday. In fact, Friday's calendar day high temperature will be at midnight with temperatures falling and then wavering in the 40s and 50s F through the day Friday beneath insolation limited by extensive stratocumulus and even isolated showers in the cyclonic flow region beneath the main upper-level trough. Occasional northwesterly winds gusting 25 to 35 mph will further exacerbate the chill of these much cooler temperatures. The seasonable cool airmass will support high temperatures in the 50s and low-60s F on Saturday and low temperatures in the mid-30s to low-40s F Saturday morning and Sunday morning. Uncertainties in lingering cloud cover Friday night and the positioning of a surface anticyclone decrease confidence in how widespread frost will be those mornings, dependent on how optimal radiational cooling and BL decoupling are. It is worth noting that global ensemble model and NBM-based probabilities of low temperatures below 36 F, a reasonable proxy for initial frost formation, have been slowly increasing for low-lying and rural areas. Global model guidance is in good agreement that a warming trend back to above average will take place Sunday through early next week as the anticyclone migrates to the east and weak but persistent low- level WAA begins. In the southwesterly upper-level flow pattern, model guidance is having a more difficult time resolving a potential passing upper-level trough that only a small amount (<15 percent) of ensemble membership has producing light showers in minimal moisture return. Therefore, dry conditions are more than likely to prevail through the weekend and early next week. && .AVIATION /00Z TAFS THROUGH 06Z FRIDAY/... Issued at 636 PM CDT Wed Oct 14 2026 Low ceilings will spread northeast into the area overnight tonight ahead of an approaching warm front. Chances of showers and a few thunderstorms will also accompany the front, with IFR visibilities possible in heavier downpours. Look for improving conditions after the passage of the warm front with winds veering more to the south. && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ SHORT TERM...Pfahler LONG TERM...Pfahler AVIATION...Gosselin