368 FXUS63 KLSX 280731 AFDLSXArea Forecast Discussion National Weather Service Saint Louis MO 231 AM CDT Sun Sep 28 2025
.KEY MESSAGES...
- Warm days, in the 80s, and cool nights, in the 50s, continue through the 7 day forecast with no opportunities for rain.
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.SHORT TERM... (Through Tuesday) Issued at 230 AM CDT Sun Sep 28 2025
Surface high pressure over the Ozarks continues to maintain a warm but moderately dry air mass in place across our region. Another surface high in norther Iowa slowly rolls east today. A cold front with cooler and drier air behind it has made it to about the Missouri/Iowa border, but it won`t make it any further. As the surface high driving this air mass moves east, southerly flow on its back side pushes that remnant boundary northward today. The northern high becomes dominant as it shifts into the Great Lakes and toward New England on Monday. Meanwhile, ridging develops aloft centered over the middle Mississippi River area today, with its influence being strongest through about Tuesday. So while there are at least some features moving about on our weather maps, we are not going to see much change to our ongoing persistent weather pattern. We`re going to continue to see warm days with highs reaching the mid to upper 80s. These next few days will be some of our warmest with the ridge developing overhead. But light winds at night in a moderately dry air mass still allow for good cooling and temperatures dropping back off into the 50s.
Kimble
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.LONG TERM... (Wednesday through Saturday) Issued at 230 AM CDT Sun Sep 28 2025
Some degree of ridging persists over the central to eastern half of the US for the rest of the week and into the weekend. That`s going to keep our weather dry and warm for that entire time period. While there is some activity in the tropical Atlantic, it`s clear now that this will stay well away from our region. Expansive surface high pressure settling into New England but with its influence felt all the way to the Great Plains will also keep a low level easterly flow across the southern tier of the US, preventing the northward transport of Gulf or Atlantic moisture. In fact, we may even get a little bit drier air circulating around the New England surface high around midweek. With ridging aloft and a lack of significant moisture, we won`t even be able to develop enough instability for afternoon cumulus clouds most days let alone thunderstorms. Our dry fall weather continues.
To find any chance for rain we have to look beyond our current 7-day forecast into next week. By then guidance is indicating two things. First, the ridge does eventually break down with some form of troughing moving out of the western US. Second, tropical moisture locked over the Gulf for so long does finally get a chance to push northward. These are at least two ingredients that could spell better rain chances at some point next week, though the details are unclear. Greater moisture will likely lead to at least some instability for the potential for thunderstorms, and depending on how the ridge breaks down a passing trough or cold front could serve as a focus for precipitation.
Kimble
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.AVIATION... (For the 06z TAFs through 06z Sunday Night) Issued at 1027 PM CDT Sat Sep 27 2025
Current clear skies and light winds are still expected to be favorable for river fog development again between 09-14Z including at JEF/SUS/CPS with similar visibilities and ceilings as what we had early on Saturday morning. Otherwise, expect dry and VFR conditions with continued light winds.
Britt
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.LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. &&
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WFO LSX
NWS LSX Office Area Forecast Discussion