620 FXUS63 KLSX 091827 AFDLSX Area Forecast Discussion National Weather Service Saint Louis MO 127 PM CDT Mon Jun 9 2025 .KEY MESSAGES... - Quiet and dry conditions are expected tomorrow and Wednesday, and likely Thursday as well. - A warming trend is increasingly likely late in the work week, with temperatures climbing back to near or slightly above average, and potentially touching 90 degrees. - Active and showery conditions are likely to return Friday through the weekend, although confidence is somewhat low regarding exactly when precipitation will return. && .SHORT TERM... (Through Late Tuesday Night) Issued at 126 PM CDT Mon Jun 9 2025 Mild and dry conditions have settled in for a few days across the area thanks to northwest flow and a continental post-frontal airmass. While some sporadic cumulus is evident on visible satellite in a few areas, and there is some high resolution guidance that suggests that a few very weak showers may develop later in the afternoon, it`s very unlikely that this activity would amount to much more than virga or perhaps a few sprinkles. Otherwise, the other item of note for today is the development of breezy westerly winds, which are expected to continue the remainder of the afternoon and diminish in the evening. This pattern is expected to continue through tomorrow as well, although a reduced pressure gradient is likely to result in weaker wind speeds. With temperatures forecast to reach near 80 degrees and dewpoints in the upper 50s to low 60s, tomorrow is expected to be a comfortable day throughout the area, with sunny skies also likely to persist. BRC && .LONG TERM... (Wednesday through Next Monday) Issued at 126 PM CDT Mon Jun 9 2025 As we head into the middle of the week, an upper level ridge is expected to slowly build east and into the area, and persistent southerly low level flow will develop as well. Initially this is expected to produce a modest warmup beginning Wednesday, with ensemble mean temperatures generally in the mid to upper 80s area- wide. Confidence is slightly higher that these warmer values will be realized as guidance has slowed the arrival of higher humidity and precipitation, and we may even make a run at 90 degrees in a few spots. Similar temperatures are increasingly likely Thursday as well, which continues to trend drier and drier. From Friday onward though, ensemble guidance continues to depict a northward surge in rich moisture, bringing the return of shower and thunderstorm chances to the area. Ensemble mean precipitable water values continue to be projected near or slightly higher than the 90th percentile of climatology, which this time of year is roughly 1.6 inches. However, this influx of moisture continues to gradually slow down in ensemble projections, and the core of this airmass remains slightly to our south. Regardless, precipitation chances do steadily increase Friday through the weekend, although the day to day probabilities fluctuate considerably due to the influence of a subtropical wave undercutting the longwave ridge. This feature, along with other smaller scale impulses, are likely to provide a modest forcing boost that will dictate when and where showers and thunderstorms form, and likewise which areas will see the most rainfall. Given the projected moisture parameters, localized pockets of heavy rain will at least be possible, but whether or not this will have the potential to produce more than just beneficial rain remains to be seen due to the heavy influence of smaller scale features. Meanwhile, ensembles also project increasing instability throughout this period, but with the longwave ridge overhead, the most significant wind shear is likely to exist farther north near the primary jet stream. Likewise, higher probabilities for severe thunderstorms exist farther to the north during this timeframe, most notably across the northern Plains and upper Mississippi Valley regions. Still, given the influx of moisture and increasing instability potential, we can`t completely rule out some low-end probabilities due to local mid level flow enhancements from the subtropical wave. Finally, temperature forecasts late in the week become a bit less certain thanks to the influence of increasing cloud cover and precipitation, but current ensemble mean projections remain very near seasonal averages. Likewise, forecast temperature spreads increase during this period, as this is a direct result of the uncertainty surrounding day to day rounds of precipitation. BRC && .AVIATION... (For the 18z TAFs through 18z Tuesday Afternoon) Issued at 1151 AM CDT Mon Jun 9 2025 VFR conditions are expected throughout the 18Z TAF period. Skies are expected to remain mostly clear, and breezy westerly winds will gradually diminish near sunset today. Some patchy fog will be possible in river valley sites overnight and early tomorrow morning, but confidence is low that fog will become widespread enough to produce impacts at local terminals. BRC && .CLIMATE... Issued at 227 PM CDT Fri Jun 6 2025 St Louis has still not seen 90 degrees yet in 2025. The average first 90 degree reading is May 20. The most recent late 90-degree start was June 10, 2021. If St Louis doesn`t hit 90 by June 10, it will be the latest first 90 degree day since at least 1995 (June 19). The latest date of first 90 degrees on record was July 4 in both 1961 and 1912. Columbia has also not yet seen a 90 degree reading in 2025, however the average first date is much later (May 31). The latest date of first 90 degrees on record was July 14, 1904. Quincy reached 90 degrees on May 15 of this year, about 3 weeks earlier than their average first 90 degrees (June 2). Kimble && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX