


Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
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841 FXUS63 KLSX 280750 AFDLSX Area Forecast Discussion National Weather Service Saint Louis MO 250 AM CDT Sat Jun 28 2025 .KEY MESSAGES... - The chance for showers and thunderstorms will continue through Monday, with the best chances (70-80%) being Sunday and Monday. - Warm and humid conditions will continue through Sunday before a cold front on Monday brings seasonable temperatures to the area through mid next week. && .SHORT TERM... (Through Sunday Night) Issued at 247 AM CDT Sat Jun 28 2025 Quasi-zonal to southwesterly flow stretches over much of the Plains and Midwest as the upper-level ridge struggles to maintain its hold over the CONUS. Weak convergence over southeastern Missouri and southwestern Illinois continues to produce low probabilities (around 20%) for isolated showers and possibly a thunderstorm across this portion of the CWA this morning. Patchy fog can`t be ruled out through the remaining pre-dawn hours thanks to minimal dew point depressions and recent rainfall. However, persistent light winds are expected to mostly mitigate this threat. Subtle disturbances riding the periphery of the ridge will keep a continuous stream of mid to upper-level clouds feeding into the CWA through the day, mainly along and south of I-70. This will keep temperatures subdued in this portion of the CWA compared to as of late, with values struggling to warm out of the 80s where cloud cover is more persistent and dense. Where sunlight can be more consistent - mainly north of I-70 - afternoon highs around 90 and into the low 90s are expected. What this means for the chance for showers and thunderstorms today is uncertain, as CAMs have been fluctuating in the occurrence and coverage of convection. Reasons for this are likely the aforementioned cloud cover limiting heating, as well as subtle height rises seen in some guidance. Where instability can build, SBCAPE will be similar to yesterday, with 2,500 J/kg or higher forecast. However, bulk shear is weaker among the majority of guidance, with only 5-10 kts expected. All this leads to lower chances for scattered showers and thunderstorms this afternoon compared to yesterday, with chances (30%) being maximized over southeastern Missouri where a weak front and subtle boundaries from previous convection will exist. Sunday is similarly forecast, though the chance for showers and thunderstorms greater (60-80%). This is due to falling heights as an upper-level trough digs into the Midwest, an approaching cold front, and subtle disturbances rippling through the flow over the Midwest. We`ll have to keep our eye on a complex of storms that guidance has consistently been dropping southward out of Iowa Sunday evening and overnight. The most favorable track for this system is just west of the CWA where instability is maximized, but these weakly forced systems are notorious for changing trajectory as lead time decreases and subtle features become increasingly resolved. Elmore && .LONG TERM... (Monday through Friday) Issued at 247 AM CDT Sat Jun 28 2025 At the start of the workweek, a trough will be digging southeastward into the Midwest per deterministic and ensemble guidance, pushing Sunday`s cold front further southward. This front will serve as the focus for showers and thunderstorms as the lift from the trough increases, though guidance still varies on the front`s placement on Monday. While it is generally expected to be stretched from the Ohio Valley into the Mid South, if it is too far south of the CWA, much of the area will be dry on Monday. If the front is further north and closer to the CWA, portions of the CWA will see showers and thunderstorms. With this solution, the most likely (60-80%) areas for rainfall are southeastern Missouri and southwestern Illinois, and this is supported by a majority of guidance. The more notable story with this front is the post-frontal airmass. As northwesterly flow aloft ushers in an area of high pressure at the surface, temperatures Tuesday through Thursday will be more seasonable than they have been as of late. Guidance has actually trended a couple of degrees cooler over the last couple of initializations, with ensemble means favoring highs in the mid to upper 80s for much of the CWA. This relative cool down will be short lived, as guidance continues to converge on a solution favoring an upper-level ridge building back into the Midwest Friday into next weekend. While the timing and amplitude of this ridge vary notably among guidance, the general pattern favors warming temperatures and a return of more widespread low rain chances. Elmore && .AVIATION... (For the 06z TAFs through 06z Saturday Night) Issued at 1033 PM CDT Fri Jun 27 2025 Showers and thundestorms have moved out of the area, and dry weather is expected the rest of the period. There is a low chance (20-30%) for showers and thunderstorms on Saturday afternoon, but this chance is expected to stay just south of COU/JEF/STL/SUS/CPS. Some fog may develop late tonight into early Saturday at all of the terminals, so I have added a TEMPO group between 09-13Z for MVFR visiblities. Otherwise expect winds to stay under 7 knots through the period. Britt && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX