


Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
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747 FXUS63 KLSX 150310 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 1010 PM CDT Mon Jul 14 2025 .KEY MESSAGES... - Showers and thunderstorms are expected again Tuesday afternoon. A few strong storms with gusty winds are possible. Some storms may also produce locally heavy rain and localized flooding. - Temperatures are expected to remain within a few degrees of normal through the rest of the week with a chance for mainly afternoon thunderstorms. && .SHORT TERM... (Through Late Tuesday Afternoon) Issued at 211 PM CDT Mon Jul 14 2025 Widely scattered showers and thunderstorms along and south of I-44 in Missouri into parts of southern Illinois will persist into early evening before dissipating with the loss of daytime heating. The RAP is showing around 1500-1700 J/Kg in these areas this afternoon, but very little deep-layer shear, so severe storms are unlikely. The storms aren`t moving very fast though, and will have to be monitored for potential localized flooding through the evening. Areas that receive rain this afternoon and evening will be susceptible to fog development again late tonight, so another Dense Fog Advisory may be needed, though confidence is not high enough to issue at this time. The upper trough which was stretching from the Upper Midwest into the southeast Plains has moved east into the Ohio Valley today. The southern end of this trough has fractured into a vorticity chain stretching from southwest Texas up into southwest Missouri and sandwiched between ridges over the Southeastern and Southwestern U.S. The vort chain will drift northeast across Missouri and Illinois through Tuesday as the two ridges slowly close ranks over the lower Mississippi Valley. The general effect on sensible weather on Tuesday will be more widespread afternoon and evening convection, mostly along and south of the I-70 corridor. Short range guidance suggests there will be more instability with MLCAPE in excess of 2000 J/Kg, as well as more 0-6km shear up to around 25kts. This would be good enough for convection to get more organized into marginally severe clusters and possibly some linear structures with gusty winds up to around 60 mph, much like what happened Sunday afternoon. The potential for locally heavy rain will continue as P-wat values are forecast to be around 2 inches, and forecast soundings show the warm cloud depth in excess of 14,000 ft. Storms should diminish in strength and coverage during the evening with the loss of diurnal heating. Carney && .LONG TERM... (Tuesday Night through Next Monday) Issued at 211 PM CDT Mon Jul 14 2025 The forecast for the long term remains virtually unchanged. The flow aloft becomes quasi-zonal across the Mid Mississippi Valley Wednesday and remains that way at least through the end of the week. The deterministic GFS and NAM show a compact short wave (most likely enhanced by an MCV) moving across Minnesota and Iowa on Wednesday which begins dragging a cold front into the Upper Midwest. Another wave moves across the Upper Midwest and southern Canada in the Thursday-Friday time frame which attempts to push the front farther south into central Missouri and southern Illinois. The second short wave looks fairly weak, so the extent of the effective front`s southward progression may be controlled more by convection and outflow boundaries than synoptic scale forcing. This puts a good deal of uncertainty in frontal position for the end of the week. The interquartile range if high temperatures in the LREF increases from 2-4 degrees on Tuesday and Wednesday to 5 to 9 degrees for Thursday and Friday with the front draped (somewhere) across our forecast area. The front will also be a focusing mechanism for afternoon and evening convection, further increasing the uncertainty in the afternoon temperature forecast. Models have been consistently showing the Southeast U.S. ridge building westward into the Mississippi Valley late Friday into Saturday. This will bring a persistent south to southwesterly low level flow back to Missouri and Illinois which will push the front back into Iowa and northern Illinois for the weekend. The interquartile range of temperatures remains fairly wide, most likely due to differences in how strong the ridge becomes over the Mississippi Valley. However, the overall range increases a few degrees each day Saturday through Monday indicating a warming trend during that period. Carney && .AVIATION... (For the 06z TAFs through 06z Tuesday Night) Issued at 1005 PM CDT Mon Jul 14 2025 VFR conditions are expected at the start of the period, but patchy fog will be possible overnight through early tomorrow morning in river valley locations. While we do not expect fog to be as widespread or as dense as the previous night, some visibility reductions will be possible, with best chances at fog-prone terminals like SUS/JEF/CPS. Any fog that does develop tonight is likely to dissipate quickly tomorrow morning. While VFR conditions are expected through the rest of the morning, another round of scattered showers and thunderstorms is likely tomorrow, with best chances at St. Louis area terminals. While this activity will be scattered and some terminals may not be directly impacted, those terminals that do see a thunderstorm overhead will likely observe bursts of heavy rain, lightning, and occasionally gusty wind. Reduced visibility and ceiling categories would also be likely in that scenario. BRC && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX