Storms trained across southeastern portions of Missouri with several rounds of heavy rain. This produced flash flooding.
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The episode as NWS LSX wrote it up.
Storms trained across southeastern portions of Missouri with several rounds of heavy rain. This produced flash flooding.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS St. Louis, MO wrote its last area forecast discussion before the first event at Aug 9, 8:45 AM CST, 2 hours 50 minutes earlier.
Area Forecast Discussion...Updated National Weather Service Saint Louis MO 945 AM CDT Thu Aug 9 2018 .UPDATE... Issued at 931 AM CDT Thu Aug 9 2018 Have increased PoPs across srn portions of the CWA thru the afternoon into the evening hours. Weak stationary fnt remains across this region helping support nearly stationary SHRA and TSRA. Mdls show 850mb moisture convergence across this region thru the morning hours, but dissipating somewhat during the afternoon. Latest CAMs support this soln, but may hold on longer into the afternoon than currently forecast. Regardless, any precip is expected to dissipate during the evening hours with loss of heating. As mentioned, ongoing storms are nearly stationary and may result in localized flooding. Obviously, these conditions will be closely monitored throughout the day. Tilly && .SHORT TERM... (Through Late Tonight) Issued at 332 AM CDT Thu Aug 9 2018 Patchy dense fog has developed once again early this morning, mainly over river valleys and portions of southwestern IL. This fog should dissipate by 8 AM. Main forecast issue will be the weak frontal boundary that had moved through the forecast area yesterday and has stalled out just south of MO/AR border. This boundary will be the focus of showers and storms today across portions of southeast MO and southern IL as an upper level shortwave trof lifts east northeast out of AR. Expect activity to develop by mid morning and persist through the day before diminishing with loss of daytime heating. How far north the showers and storms develop will depend on track of upper level shortwave. For now should remain south of the STL metro area. Warmer temps expected today with highs in the upper 80s to mid 90s for most locations. However, will only see mid 80s over portions of southeastern MO due to lingering cloud cover and precipitation. By late tonight, a cold front is expected to approach northeastern Missouri and west-central Illinois. However, precipitation chances to hold off. So dry and mild conditions with lows in the mid 60s to low 70s expected. Byrd .LONG TERM... (Friday through Wednesday) Issued at 332 AM CDT Thu Aug 9 2018 A slow moving cold front will sink southward through the bi-state region during the day Friday. Not much has changed with relatively minor differences between guidance. Most of the day remains dry, especially south of I-70. The front stretches from approximately Chicago to Kansas City during the late morning and early afternoon. A narrow axis of moisture convergence will stretch along the front, co-located with a narrow corridor of 2-3K J/kg MUCAPE. Instability maxes out during the late afternoon with the front just north of the St. Louis metro area. Provided relatively marginal shear and slow movement of the front, storms should not be too much of a concern with short window of time for development and somewhat limited coverage. The line is likely to be broken/scattered. General consensus suggests weakening storms will slowly sink south through the St. Louis area around/after sunset with loss of diurnal heating. The weekend consists of many moving parts around the immediate forecast area, but for now, conditions look dry and quiet. The front continues to move south into Saturday. Depending on its progress, portions of southeast Missouri and far southwest Illinois could see a few showers/isolated storms Saturday afternoon, mainly near/south of Farmington vicinity. Cooler and drier air filters in behind the front thanks to northerly flow resulting from troughing over the Great Lakes and ridging over the northern plains. The Great Lakes trough develops into a closed upper low over the Ohio Valley, while surface high builds in over Iowa. Upper ridging over the northern plains fights to nudge east into early Monday. Surface high in conjunction with dry/cool source of northerly flow should make for pleasant weather this weekend into early next week. Temperature will be slightly below to near normal. Despite timing differences between GFS/ECM, it generally looks as though there is a decent bet for a return to active weather beyond Monday. Ridging over the northern gulf will assist in steering low pressure through the area through the midweek period. A warm front running well ahead of the system may result in showers and storms as soon as Monday night into Tuesday morning. The low drives northeast with increasing chances for showers and storms from Tuesday into Wednesday. Cloud cover and precip could keep temperatures at bay with highs ranging through the 80s. Maples && .AVIATION... (For the 12z TAFs through 12z Friday Morning) Issued at 635 AM CDT Thu Aug 9 2018 Fog has developed in the river valleys affecting KSUS and KCPS, so kept mention of MVFR/IFR visibilities through 13z. Otherwise, VFR conditions to persist through forecast period with light and variable winds. SPECIFICS FOR KSTL: VFR conditions to persist through forecast period with light and variable winds. Byrd && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && WFO LSX
Hazardous Weather Outlook National Weather Service Saint Louis MO 421 AM CDT Thu Aug 9 2018 ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027- 034>036-041-042-047>052-059>065-072>075-084-085-099-100930- Greene IL-Macoupin IL-Montgomery IL-Bond IL-Fayette IL-Clinton IL- Marion IL-Washington IL-Randolph IL-Adams IL-Brown IL-Pike IL- Calhoun IL-Jersey IL-Madison IL-Saint Clair IL-Monroe IL-Knox MO- Lewis MO-Shelby MO-Marion MO-Monroe MO-Ralls MO-Pike MO-Boone MO- Audrain MO-Moniteau MO-Cole MO-Osage MO-Callaway MO-Montgomery MO- Lincoln MO-Gasconade MO-Warren MO-Saint Charles MO-Franklin MO- Saint Louis MO-Saint Louis City MO-Jefferson MO-Crawford MO- Washington MO-Saint Francois MO-Sainte Genevieve MO-Iron MO- Madison MO-Reynolds MO- 421 AM CDT Thu Aug 9 2018 This hazardous weather outlook is for portions of eastern and central Missouri as well as west central and southwest Illinois. .DAY ONE...Today and Tonight There is a chance for thunderstorms this afternoon and evening, south of a line running from Cuba, MO to Sparta, IL. .DAYS TWO THROUGH SEVEN...Friday through Wednesday There is a chance of thunderstorms for at least portions of the area Friday through Sunday and again Tuesday into Wednesday. .SPOTTER INFORMATION STATEMENT... Spotter activation is not anticipated through tonight. Maples
The St Louis radar (KLSX), 119 km away, was scanning. The volume nearest the first event began at 17:33 UTC.
1 flash flood. Local standard time, as filed.
Up to five inches of rain fell in a short amount of time causing flash flooding. Coldwater and Alexander Creeks were well above bankfull, flooding nearby roadways.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Missouri in 2018Every state in 2018This day in weather historyWarnings in Missouri, August 2018
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 783288.