


Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
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007 FXUS63 KLSX 160339 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 1039 PM CDT Wed Oct 15 2025 .KEY MESSAGES... - Above normal temperatures will continue through Friday. There may be some sprinkles across parts of the area this evening, but accumulating rainfall is not expected. - Much-needed rainfall is still expected on Saturday ahead of a strong cold front. There is a conditional threat for severe storms Saturday, although confidence in severe weather remains low at this time. && .SHORT TERM... (Through Late Thursday Night) Issued at 237 PM CDT Wed Oct 15 2025 The weather pattern continues to be dominated by a high amplitude ridge over the central U.S. and long wave troughs to the west and east. The warm and (mostly) dry weather will therefore continue through the short term. The 850mb high which is currently centered over central Missouri will drift into western Illinois by early this evening. Weak moisture convergence on the western side of the high is producing some sprinkles across parts of central and northeast Missouri, and there have been several reports of trace to 0.01 inch of rain. Short range guidance continues to show the potential for very light precipitation into this evening due to this moisture convergence. However forecast soundings have a very dry layer below 850mb so accumulating rainfall is very unlikely. Will therefore keep "sprinkles" in the forecast for this evening with PoPs below 15 percent. The strongest moisture convergence moves into west/northwest Illinois late tonight and Thursday, and with that the chance for any further precipitation should end in the short term. Temperatures will continue to be well above normal through Thursday night with highs in the 80s and lows in the upper 50s to low 60s. Carney && .LONG TERM... (Friday through Next Wednesday) Issued at 237 PM CDT Wed Oct 15 2025 The primary concern in the medium range is the potential for severe thunderstorms on Saturday. The upper level pattern continues shifting east on Friday, which brings return flow to the Plains and Mississippi Valley. The long wave trough over the western U.S. opens up and lifts across the northern Plains, forcing low level cyclogenesis which develops a cold front stretching from Minnesota to northern Texas by early Friday evening. The front stalls Friday night as the mid-upper level wave continues northeast into Canada. There should be plenty of time Friday and Friday night for southerly flow to bring 60+ degree dew points back into the Mid Mississippi Valley ahead of the front. Meanwhile, another short wave trough digs into the Plains Saturday and continues east into the Mississippi Valley Saturday night. This wave ultimately pushes the cold front through Missouri and Illinois by early Sunday morning. There continue to be timing differences between the deterministic GFS and ECMWF with regards to the passage of the front through the area. There are also timing differences between the 00Z-06Z-12Z runs of these models. The latest runs are showing a slower eastward progression of the front, and more instability with better surface heating by early afternoon. However, the highest instability is farther to the west and southwest than earlier runs. Also, this higher instability is somewhat questionable as the low level jet will be producing moisture convergence in the warm sector, likely resulting in clouds and showers which would limit heating. All of this adds up to a great deal of uncertainty in the forecast for Saturday. Still think the most likely scenario on Saturday is for widespread showers with scattered sub-severe thunderstorms producing much-needed rainfall across the area, mainly in the afternoon and evening. I would like to see more run-to-run consistency, and agreement between models before getting too concerned about severe thunderstorms, however the potential is there, particularly since there will be 50+ kts of deep layer shear. Forecast soundings are not indicating particularly low LCLs, but rotating storms would be possible given the shear, particularly if the deterministic GFS`s MLCAPE of 1200+ J/Kg is realized. Unfortunately, the uncertainty in the forecast may not improve until the kicker short wave is sampled by the upper air network Friday night. The remainder of the medium range looks relatively quiet. Temperatures cool to near or slightly below normal for Sunday behind the front. There are some indications that there will be lingering showers on Sunday morning, although the latest model runs are now completely dry. Temperatures warm a few degrees above normal again Monday and there may be another chance for rain Tuesday as another fast-moving short wave moves through the Mississippi Valley, however it looks like the moisture return ahead of the wave will be limited since it will be progressing quickly through the region. The cold front associated with Tuesday`s wave will bring another shot of cooler air midweek. Carney && .AVIATION... (For the 06z TAFs through 06z Thursday Night) Issued at 1039 PM CDT Wed Oct 15 2025 VFR flight conditions and east-southeasterly winds are expected to prevail at the local terminals through the TAF period. Elmore && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX