A cold front moved through the region with several slow moving storms developing along it. One that moved through the St.
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS LSX wrote it up.
A cold front moved through the region with several slow moving storms developing along it. One that moved through the St. Louis Metro area produced brief heavy rain and isolated 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 Aug 15, 7:28 PM CST, 1 hour 27 minutes earlier.
Area Forecast Discussion...Updated National Weather Service Saint Louis MO 828 PM CDT Sat Aug 15 2020 .UPDATE... Issued at 809 PM CDT Sat Aug 15 2020 Thunderstorms have persisted in the St. Louis metropolitan area and southwestern Illinois longer than previously expected along the cold front draping southeast across the central and eastern CWA. Outflow boundaries from a strong thunderstorm earlier in south St. Louis and a cluster of ongoing thunderstorms in Illinois have triggered additional activity as they interact with MUCAPE over 3000 J/kg. In addition to the abundant lightning, DCAPE over 1000 J/kg suggests strong winds seem to be the most pressing threat from the storms. Once the combined forcing from the cold front and numerous outflow boundaries abate, storms should dissipate cooler, drier conditions will take hold. MRB && .SHORT TERM... (Through Late Sunday Night) Issued at 226 PM CDT Sat Aug 15 2020 The surface cold front is currently laid out from northern Oklahoma, through central Missouri, into central Illinois and the Great Lakes area. Though the front is not producing a sharp wind shift or much precipitation, it's easily identified by the clear sky and lower dewpoints in its wake. Deep moisture convergence remains weak along the front, so while the CAMs indicate that showers and thunderstorms will develop this afternoon, uncertainty remains as to whether peak heating will be enough to stimulate robust storm development. Thus, have kept a slight chance of showers and thunderstorms along the front as it continues to slide southeast through the area this afternoon and early evening. Small showers have begun to pop up across east-central Missouri and far west- central Illinois along the front. Ahead of the front 2000-3000 J/kg of MUCAPE and 15-20 kts of 0-6 km bulk shear indicate that if thunderstorms do develop, they will be short-lived. However, I cannot rule out a few becoming strong enough to produce hail and damaging winds. The passage of this front will mark the transition from a warm and very wet regime to a cooler and widely drier pattern that will last most of the upcoming week. A surface high will build in behind the front, bringing clearing skies and dry northwesterly flow that will facilitate effective cooling overnight. Temperatures are expected to reach the upper 50s to lower 60s overnight and remain cool on Sunday with below normal highs in the low to mid 80s. Dry weather, mostly clear skies, and low dewpoints will make Sunday a beautiful day and great end to the weekend. MRM .LONG TERM... (Monday through Next Saturday) Issued at 226 PM CDT Sat Aug 15 2020 Little has changed in the extended period. The mid-level ridge over the west will stay largely in place while the trough over the eastern CONUS deepens into the beginning of next week. This pattern will continue through the end of the period, leaving the mid- Mississippi River Valley in persistent northwesterly flow. Multiple disturbances will propagate through this northwesterly flow, the first coming through Monday afternoon into Tuesday, driving a largely dry surface cold front through the CWA. Ahead of the front on Monday, westerly flow at the surface will encourage temperatures to climb back into the mid to upper 80s. The operational GFS and NAM are beginning to indicate some deep moisture convergence along this boundary as it moves south through the CWA. Given that just these models are indicating the potential for precipitation along this boundary while the rest of operational and ensemble guidance points towards a dry frontal passage, have kept the dry NBM forecast. Behind the front, 850 temperatures cool into the low teens and on Tuesday high temperatures will struggle to get out of the low 80s with lows bottoming out in the low 60s and even upper 50s. Tuesday will likely be the coolest day of the period. Several more mid-level disturbances will move through the northwesterly flow over the extended period, but the lack of moisture and the lingering low-level and surface highs will keep the area largely dry. By the end of the work week the low-level and surface highs begin to deteriorate and shift eastward. Surface and low-level flow veers southerly and southwesterly, and surface temperatures will creep back to near normal by the weekend. MRM && .AVIATION... (For the 00z TAFs through 00z Sunday Evening) Issued at 606 PM CDT Sat Aug 15 2020 VFR conditions are firmly in place for central/northeastern MO and west-central IL, including KCOU and KUIN. Thunderstorms associated with a weak cold front have shot the gap between KSTL and KSUS, leaving KCPS as the only terminal still at risk for ceiling/visibility restrictions. By 02Z, that threat will diminish as the cold front departs the St. Louis metropolitan area. The high pressure overspreading the area behind the cold front will keep conditions VFR through the period. MRB && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && WFO LSX
Hazardous Weather Outlook National Weather Service Saint Louis MO 241 PM CDT Sat Aug 15 2020 ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027- 034>036-041-042-047>052-059>065-072>075-084-085-099-161945- 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 IL-Saint Francois MO-Saint Louis City MO-Saint Louis MO- Sainte Genevieve MO-Shelby MO-Warren MO-Washington IL-Washington MO- 241 PM CDT Sat Aug 15 2020 This Hazardous Weather Outlook is for portions of eastern and central Missouri as well as west central and southwest Illinois. .DAY ONE...Tonight. There is a slight chance for thunderstorms across east-central and southeast Missouri and southwest Illinois late this afternoon and early this evening. An isolated thunderstorm could become strong to severe, producing limited hail and damaging winds. .DAYS TWO THROUGH SEVEN...Sunday through Friday. No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed through this evening for portions of southeast Missouri and southwest Illinois. MRM
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ST LOUIS MO
909 PM CDT SAT AUG 15 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0907 PM HEAVY RAIN 1 NE EDWARDSVILLE 38.81N 89.95W
08/15/2020 M1.92 INCH MADISON IL COCORAHS
1.92 INCHES IN 38 MINUTES.
&&
GKSPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ST LOUIS MO
943 PM CDT SAT AUG 15 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0941 PM HEAVY RAIN CRESTWOOD 38.56N 90.38W
08/15/2020 M1.40 INCH ST. LOUIS MO PUBLIC
1.40 INCHES OF RAIN THIS EVENING.
&&
GKSPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ST LOUIS MO
945 PM CDT SAT AUG 15 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0945 PM HEAVY RAIN EDWARDSVILLE 38.80N 89.97W
08/15/2020 M2.80 INCH MADISON IL PUBLIC
2.80 INCHES OF RAIN THIS EVENING.
&&
GKSThe St Louis radar (KLSX), 41 km away, was scanning. The volume nearest the first event began at 02:55 UTC.
2 flash flood. Local standard time, as filed.
Up to four inches of rain fell in a two hour period causing flash flooding. Portions of Watson Road had up to a foot of water on it. Also, Union Road was flooded where it parallels I-55 near exit 200.
Up to four inches of rain fell in a two hour period causing flash flooding. Several roads were flooded in the southern portions of the city including Watson Road and roads on the eastern end of Carondelet Park near Interstate 55.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Missouri in 2020Every state in 2020This day in weather historyWarnings in Missouri, August 2020
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: 923813, 923816.