


Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
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088 FXUS63 KLSX 081833 AFDLSX Area Forecast Discussion National Weather Service Saint Louis MO 133 PM CDT Tue Jul 8 2025 .KEY MESSAGES... - Scattered thunderstorms are expected to track southeast through the region today. A few thunderstorms could be strong, including the potential for isolated severe thunderstorms with winds gusts to 60 mph and locally heavy rain. - Warm, seasonable temperatures will persist through the next several days along with periodic chances for thunderstorms impact the region. && .SHORT TERM... (Through Late Wednesday Night) Issued at 130 PM CDT Tue Jul 8 2025 Thunderstorm potential will be the primary focus this afternoon into this evening as an upper level trough and MCV (mesoscale convective vortex) rotate southeastward through late this evening. IR satellite shows a broad expanse of broken/overcast clouds extending from northern MO through portions of IA/IL/WI. Clouds are associated with the MCV, remnant of a convective complex that developed over SD/NE last evening. Another area of clouds and convection extend from eastern OK into southern IN. In between the two areas, skies have remained mostly clear, allowing instability to build ahead of the approaching MCV. As of 18z, SPC mesoanalysis shows a what little CIN that exists extending from Kansas City roughly just west of Quincy, IL. Where skies have remained mostly clear, surface instability has climbed with 2500 J/kg of SBCAPE roughly along and north of the I-44 corridor into southwestern IL along I-70. This not only jives pretty well with guidance from prior runs, including this morning, and maybe even on the higher end. HREF means showed SBCAPE of 2-2.2k with deterministic hi-rese guidance (RAP/HRRR) plotting 2.5-3k this afternoon. Moisture is no question with dewpoints in the upper 60s to low-70s and PWATs around 1.7" per SPC mesoanalysis. Thunderstorms will certainly have the moisture to produce efficient rainfall with locally heavy rain, resulting in ponding/nuisance flood in areas impacted by multiple cells. Though soundings are showing a particularly classic inverted-V, 50-100mb dewpoint depressions in the realm of 10-13C suggest localized downbursts with marginally severe wind gusts (60 mph) are possible. Hail cannot be entirely ruled out, but what does fall is likely sub-severe with mid-level lapse rates at 5.5-6C and competing updrafts as scattered convection become more numerous in time. Despite some slight spatial/temporal variability between deterministic hi-res models, paintball plots (simulated reflectivity >40 dBZ) show a general consensus that the best timeframe for development runs from near KCOU to just south of KPPQ. IR satellite is showing a notable uptick in development in this region, increasing confidence that this will be the region for focused initiation. Thunderstorms then move southeast through approximately 8-9 p.m. as thunderstorms progress southeast and weaken after sunset. Once thunderstorms clear to the southeast and dissipate late this evening, clouds likely hang on for some time tonight before partial clearing works into northeast MO. There is some hint at patchy fog development running from central to northeast MO, but cloud cover may not clear quick enough before sunrise, limiting fog potential. This will be something to monitor through tonight, but even if fog develops, it is not expected to be anything significant with the limited time to take advantage of clearing. By Wednesday, mostly dry conditions are expected with the low chance that an isolated shower may develop. However, much of the potential will reside outside the CWA. Should anything develop, the best chance (30-40%) will line up along the southeast portion of the CWA with chances quickly tapering to the north and dropping through the day as surface high pressure builds in from the northwest. Maples && .LONG TERM... (Wednesday Night through Monday) Issued at 336 AM CDT Tue Jul 8 2025 The LREF is showing that the upper pattern from mid week into early next week will be highlighted by a large high over the southwest CONUS with Missouri and Illinois on the southern edge of the active westerlies. While there will be on and off chance of showers and thunderstorms over the Midwest as troughs move through the aforementioned westerlies, the best chance (40-60%) over our area will be Friday night into Saturday when there is good agreement in the global models that a upper trough and attendant cold front will move across Missouri and Illinois. While the weekend does not look like a washout, I can`t rule out heavy downpours with some of the thunderstorms given PWATS around 2". Temperatures through the period will be close to July normals ranging from the mid 80s to around 90 degrees. The NBM is showing the warmest day on Friday when most areas will see highs in the low 90s and heat indexes near 100 degrees ahead of the front. Britt && .AVIATION... (For the 18z TAFs through 18z Wednesday Afternoon) Issued at 1232 PM CDT Tue Jul 8 2025 The primary focus will be the potential for showers and thunderstorms this afternoon into this evening, a few of which could be strong to marginally severe. The primary threats will be locally heavy rain and gust winds, including isolated gusts approaching 60 mph in the strongest thunderstorms. A few showers have already developed around KUIN with potential trending southward as more robust convection initialized across central and east-central Missouri into southwestern Illinois. Considering the slight difference in hi-resoultion guidance and scattered nature of convection, TEMPO groups were utilized to convey the period of greatest impact. This may be adjusted in later amendments should initialization of activity be departed from current thoughts. The strongest cells are likely to result in MVFR ceilings/visibility for brief periods. Outside of the thunderstorm potential, VFR conditions are expected. A few showers and thunderstorms may linger into this evening, but generally speaking, thunderstorms will move south of the terminals and weaken after sunset. Light/variable surface winds will persist into Wednesday. Maples && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX