Training storms moved through portions of southeast Missouri and southwestern Illinois with up to 4 inches of rain in a short amount of time. There were several reports of flash flooding.
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The episode as NWS LSX wrote it up.
Training storms moved through portions of southeast Missouri and southwestern Illinois with up to 4 inches of rain in a short amount of time. There were several reports of 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 Jul 15, 11:21 PM CST, 31 minutes earlier.
Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 1221 AM CDT Fri Jul 16 2021 .SHORT TERM... (Through Late Friday Night) Issued at 330 PM CDT Thu Jul 15 2021 Two shortwaves currently noted in water vapor imagery over the Central Plains are making their way eastward along the periphery of an upper-level trough, helping spawn convection along a slow, southward moving cold front. Ahead of this front and associated convection, SPC mesoanalysis shows MUCAPE of about 3,000 J/kg over the Middle Mississippi Valley. Shear in the 0-6 km layer of around 30 kts is also noted along and north of the front, creating a narrow corridor for strong to severe storm potential along the front this afternoon and evening. As the cluster of storms in west-central Illinois continue eastward out of the CWA, our focus turns to the storms that have recently developed in western and central Missouri. These and additional storms that form in the CWA over the next several hours will carry mainly a damaging wind threat. However, the main threat with these storms continues to be heavy rainfall and the potential for isolated flooding. Precipitable water is roughly 1.75" over the CWA, allowing for stronger cores to quickly be able to drop plenty of rain and produce minor flooding along drainage ditches and ponding on roads. With upper-level flow roughly parallel to the front, storms may potentially train over the same area. The potential flood threat will come from these training storms this evening and overnight, but I'm still uncertain in their ability to train at this point. Some recent CAM runs progress convection through the CWA rather quickly tonight, and this faster solution would limit the flooding potential. Near day-break tomorrow, the front will be roughly oriented along the I-44 corridor in Missouri and the I-70 corridor in Illinois. The greatest precipitation chances will be along and south of this corridor where forcing is greatest. MUCAPE along and ahead of the front will be around 1,500 J/kg during peak heating, but ensemble and deterministic guidance have 0-6 km shear less than 30 kts, so my confidence in organized severe storms is not high at this time. With precipitable water forecast to still be around 1.75" and mid-level flow roughly parallel to the front, training showers and storms capable of heavy rainfall and localized flooding will still be a threat. Elmore .LONG TERM... (Saturday through Next Thursday) Issued at 330 PM CDT Thu Jul 15 2021 On Saturday, the broad, weak upper-level trough will have only shifted slightly eastward relative to our CWA. Deterministic guidance has a shortwave digging southward along the western periphery of this trough over the Middle Mississippi Valley, which will help push the front a little further south. This will keep the low chance for scattered convection mainly along and south of I-70 during the day. A similar scenario will be present on Sunday, as the aforementioned shortwave slowly moves southward, nudging the front a little further south and confining the best chances for convection to southeastern Missouri. For the remainder of the extended period, each of the four clusters in the WPC ensemble cluster analysis show a stout ridge building across the western U.S. with troughing over the eastern portion of the country. While finer details remain uncertain at this lead time, the agreement among ensemble guidance gives me high confidence in higher temperatures and moisture remaining shunted out of the CWA, leading to calm weather and temperatures remaining at or just below climatological norms for this time of year. Elmore && .AVIATION... (For the 06z TAFs through 06z Friday Night) Issued at 1218 AM CDT Fri Jul 16 2021 Thunderstorms are now mainly south and east of the terminals, and save for an errant rumble of thunder, should stay clear of them tonight. Waves of showers, all of which could bring VSBY restrictions as low as IFR, are expected tonight at the mid-Missouri and St. Louis terminals. At KUIN, clearing skies and high relative humidity from earlier storms will keep a persistent fog/very low stratus threat at the terminal through sunrise. Conditions could drop to as low as IFR/LIFR at times, but I expect VSBY to bounce between flight categories through the night. CIGs are also expected to drop to MVFR overnight across the area thanks to elevated low- level moisture. Guidance continues to insist on widespread lower CIGs, possibly influenced heavily by the fog potential, but outside of brief instances I am not confident the terminals will experience lower conditions. Another round of showers and thunderstorms is expected later tomorrow morning into the afternoon, mainly affecting all terminals except KUIN (though a shower/storm cannot be ruled out there either). CIGs are forecast to remain around MVFR through the morning and into the early afternoon before lifting from west to east. Following tomorrow's precipitation, another round of fog is possible across a broader area. That being said, confidence is not high enough in that scenario to bring mention of fog into the TAFs at this time. MRB/Pfahler && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && WFO LSX
Hazardous Weather Outlook National Weather Service Saint Louis MO 741 PM CDT Thu Jul 15 2021 ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027- 034>036-041-042-047>052-059>065-072>075-084-085-099-170045- Adams IL-Audrain MO-Bond IL-Boone MO-Brown IL-Calhoun IL-Callaway MO- Clinton IL-Cole MO-Crawford MO-Fayette IL-Franklin MO-Gasconade MO- Greene IL-Iron MO-Jefferson MO-Jersey IL-Knox MO-Lewis MO-Lincoln MO- Macoupin IL-Madison IL-Madison MO-Marion IL-Marion MO-Moniteau MO- Monroe IL-Monroe MO-Montgomery IL-Montgomery MO-Osage MO-Pike IL- Pike MO-Ralls MO-Randolph IL-Reynolds MO-Saint Charles MO- Saint Clair-Saint Francois MO-Saint Louis City MO-Saint Louis MO- Sainte Genevieve MO-Shelby MO-Warren MO-Washington IL-Washington MO- 741 PM CDT Thu Jul 15 2021 This Hazardous Weather Outlook is for portions of eastern and central Missouri as well as west central and southwest Illinois. .DAY ONE...Tonight. Strong to severe thunderstorms are possible this evening across most of the area. Damaging wind gusts and heavy rainfall with localized flooding are the main threats. .DAYS TWO THROUGH SEVEN...Friday through Wednesday. Additional thunderstorms are possible across portions of the area Friday through Tuesday. Locally heavy rain is possible with thunderstorms on Friday. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report wind damage and flash flooding to the National Weather Service MRB
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ST LOUIS MO
1211 AM CDT FRI JUL 16 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1210 AM FLASH FLOOD FARMINGTON 37.78N 90.43W
07/16/2021 ST. FRANCOIS MO LAW ENFORCEMENT
DISPATCH REPORTS SEVERAL ROADWAYS COVERED
WITH WATER. THIS INCLUDES AT LEAST A HANDFUL
OF ROADS THAT DO NOT TYPICALLY FLOOD. THE
WORST OF THE FLOODING IS IN AND AROUND
FARMINGTON.
&&The St Louis radar (KLSX), 89 km away, was scanning. The volume nearest the first event began at 05:51 UTC.
2 flash flood. Local standard time, as filed.
Up to four inches of rain fell in a short amount of time causing flash flooding. Numerous roads were flooded including Illinois Route 150 just west of intersection with Illinois Route 4.
Up to four inches of rain fell in a short amount of time causing flash flooding. Numerous roads were flooded, especially in and around Nashville.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2021Every state in 2021This day in weather historyWarnings in Illinois, July 2021
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: 975418, 975426.