A cluster of strong thunderstorms over southeastern Missouri resulted in a quick 2 to 3 inches of rain in 90 minutes near the Poplar Bluff area. The storms occurred in a very weakly forced environment, however, the air mass was very moist and unstable.
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The episode as NWS PAH wrote it up.
A cluster of strong thunderstorms over southeastern Missouri resulted in a quick 2 to 3 inches of rain in 90 minutes near the Poplar Bluff area. The storms occurred in a very weakly forced environment, however, the air mass was very moist and unstable. Elevated instability was quite high, with capes up to 2000 J/kg. Very high moisture content and very weak steering flow aloft (around 10 knots of flow through the mid levels) contributed to slow and erratic storm motions and very efficient rainfall rates. Since the ground was already very moist from previous storms, runoff from this round of storms produced pockets 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 Paducah, KY wrote its last area forecast discussion before the first event at Aug 13, 5:39 AM CST, 4 hours 51 minutes earlier.
Area Forecast Discussion National Weather Service Paducah KY 639 AM CDT Fri Aug 13 2021 .UPDATE... Issued at 639 AM CDT Fri Aug 13 2021 The AVIATION section has been updated for the 12Z TAF issuance. && .SHORT TERM...(Today through Sunday night) Issued at 332 AM CDT Fri Aug 13 2021 Very low confidence forecast this morning due to the fact that most of the 00Z and later guidance has no clue about the MCS yesterday evening. This is in regards to convective trends and potential heat and humidity. Although surface winds quickly returned to southerly behind the outflow boundary, it now appears that there is a convergent boundary setting up over southeast Illinois. Meanwhile, the synoptic boundary appears to extend from southeast Iowa southwest into northwest Missouri where it gets muddled within another MCS. Aloft it appears that we may have a MCV over the region now, and there certainly could be another one upstream out of the KS/MO MCS. The main question, otherwise, is how hot we will be able to get before convection develops. The forecast has trended downward another couple of degrees, but the NBM dewpoints hold in the middle 70s, so we still have some locations across the southern half of the area where heat indices reach 100 degrees or more. With only mid and high cloud across the region and a likely dissipating trend by daybreak, substantial destabilization appears likely over most if not all of the area before the cold front arrives this afternoon. The bottom line is that scattered to numerous thunderstorms are likely to develop as early as late this morning in the vicinity of whatever boundaries remain across the region. With little quality guidance to work with decided to cap PoPs at 50%, and in general will show a slow southeast progression across the region from late morning through the evening. The consensus of guidance brings the synoptic wind shift into west Kentucky by 00Z, and then pushes it out of the region during the evening. Although the synoptic-scale guidance keeps elevated convection going behind the front through much of tonight, any potential for severe weather should end with the frontal passage. Despite the continued lack of shear, given the amount of instability that is likely to develop, some isolated damaging wind gusts could develop, especially if the storms become somewhat linear. Given the boundaries in the area a linear storm mode is certainly a possibility. Some localized heavy rainfall will be possible, as well. Low-level moisture will be slow to decrease behind the boundary, so that, coupled with mid/upper-level disturbances rotating through the area, should lead to scattered showers and thunderstorms over much of the area through the evening, and possibly into the overnight hours. Some isolated to scattered convection will be possible over the southern third to half of the area on Saturday, too. As for temperatures, stuck close to the 50th percentile of all available guidance for highs today and Saturday. Given the uncertainties with convective trends today, the middle ground seemed to be the best fit. As dry air moves in the northeast Saturday, wouldn't be surprised if that area overachieved from the middle 80s that we have forecast throughout the area. With the delayed drying trend tonight tried to lean toward the warm side of guidance for lows, and may not be warm enough. .LONG TERM...(Monday through Thursday) Issued at 332 AM CDT Fri Aug 13 2021 From Sunday through the upcoming work week, the region will be between a persistent mid-level trough located across the the Midwest and strong ridging over the southeast CONUS. At the surface, high pressure will be centered over the eastern Great Lakes, while a stationary boundary will be draped across the Mid-South. As lobes of vorticity rotate around the base of the Midwest trough, isolated to scattered showers and thunderstorms will be possible during the peak heating hours each day. On Sunday and Monday, PoPs will be confined to our far south and southeast counties which will be closest to the stationary boundary. For Tuesday through Friday, scattered PoPs will be fairly uniform across the forecast area as the stationary boundary attempts to lift north into the region. Something else to watch will be the potential for tropical moisture from the remnants of Fred to spread into the east/southeast parts of the forecast area Tuesday and Wednesday. At this time, the bulk of rain looks to remain well to our east, but the added moisture may enhance diurnal thunderstorm activity. As for temperatures, we'll see a reprieve from the heat and humidity on Sunday as high temperatures will remain in the lower to middle 80s, with dew point temperatures in the middle 60s for most locations. By Monday, dew point temperatures will again creep up into the uncomfortable range of 70 to 75 degrees and remain there through the rest of the work week. Air temperatures will slowly warm into middle 80s by Tuesday and the upper 80s for Wednesday through Friday. Overnight lows will range from the middle 60s to lower 70s at most locations. && .AVIATION... Issued at 639 AM CDT Fri Aug 13 2021 Very low confidence forecast this morning, so kept them simple. Not sure why there is an MVFR ceiling at KOWB, but figure it will not last long. Went VFR everywhere through the period. Not nearly confident enough in convective evolution today to mention SHRA/TSRA anywhere at this time. There will be some cu and plenty of mid cloud through the period. Guidance strongly suggests either MVFR fog or ceilings late tonight, but with the weak frontal passage and mid clouds, that seems unlikely. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...None. MO...None. IN...None. KY...None. && UPDATE...DRS SHORT TERM...DRS LONG TERM...DWS AVIATION...DRS
Hazardous Weather Outlook National Weather Service Paducah KY 349 AM CDT Fri Aug 13 2021 ILZ075>078-080>094-INZ081-082-085>088-KYZ001>022-MOZ076-086-087- 100-107>112-114-141000- Jefferson-Wayne IL-Edwards-Wabash-Perry IL-Franklin-Hamilton- White-Jackson-Williamson-Saline-Gallatin-Union-Johnson-Pope- Hardin-Alexander-Pulaski-Massac-Gibson-Pike-Posey-Vanderburgh- Warrick-Spencer-Fulton-Hickman-Carlisle-Ballard-McCracken-Graves- Livingston-Marshall-Calloway-Crittenden-Lyon-Trigg-Caldwell- Union KY-Webster-Hopkins-Christian-Henderson-Daviess-McLean- Muhlenberg-Todd-Perry MO-Bollinger-Cape Girardeau-Wayne MO-Carter- Ripley-Butler-Stoddard-Scott-Mississippi-New Madrid- 349 AM CDT Fri Aug 13 2021 This Hazardous Weather Outlook is for portions of southern Illinois, southwest Indiana, western Kentucky, and southeast Missouri. .DAY ONE...Today and Tonight A good chance of thunderstorms is forecast throughout the region today into tonight. A few strong storms with damaging winds will be possible along and ahead of a cold front that is forecast to make passage this afternoon into this evening. Otherwise, locally heavy rainfall and lightning will be the primary concerns. Heat index values could reach 100 degrees again this afternoon mainly across the southern half of the region. The extreme conditions, if they develop, should be short-lived with the expected thunderstorm activity providing quick relief. .DAYS TWO THROUGH SEVEN...Saturday through Thursday There is a daily chance of isolated to scattered thunderstorms through the period, mainly during the heat of the day. The activity will be focused over west Kentucky Saturday through Monday and over the entire region Tuesday through Thursday. Severe thunderstorms are not anticipated at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation cannot be ruled out this afternoon and evening. DRS/DWS
Special Weather Statement
National Weather Service Paducah KY
952 AM CDT Fri Aug 13 2021
MOZ107>109-131515-
Butler MO-Carter MO-Ripley MO-
952 AM CDT Fri Aug 13 2021
...A strong thunderstorm will impact portions of southeastern Carter,
northeastern Ripley and west central Butler Counties through 1015 AM
CDT...
At 951 AM CDT, Doppler radar was tracking a strong thunderstorm near
Budapest, or 9 miles north of Doniphan, moving east at 25 mph.
HAZARD...Winds in excess of 40 mph and pea size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor damage to outdoor objects is
possible.
This strong thunderstorm will be near...
Budapest around 1000 AM CDT.
Other locations in the path of this storm include Milltown.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 3667 9087 3683 9089 3686 9060 3668 9057
TIME...MOT...LOC 1451Z 262DEG 21KT 3676 9078
MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH
08Special Weather Statement
National Weather Service Paducah KY
1019 AM CDT Fri Aug 13 2021
MOZ109-131600-
Butler MO-
1019 AM CDT Fri Aug 13 2021
...A strong thunderstorm will impact portions of northern Butler
County through 1100 AM CDT...
At 1017 AM CDT, Doppler radar was tracking strong thunderstorms over
Milltown, or 8 miles northwest of Poplar Bluff, moving east at 30
mph.
HAZARD...Winds in excess of 40 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
This strong thunderstorm will be near...
Poplar Bluff around 1030 AM CDT.
Other locations in the path of this storm include Fisk.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
A Flood Advisory is also in effect for the area. Torrential rainfall
is occurring with the storms and may lead to localized flooding. Do
not drive your vehicle through flooded roadways.
&&
LAT...LON 3668 9063 3681 9063 3681 9066 3686 9066
3693 9034 3692 9026 3689 9025 3688 9026
3684 9022 3682 9022 3681 9020 3677 9020
3677 9019 3673 9016 3670 9016
TIME...MOT...LOC 1517Z 260DEG 26KT 3679 9057
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...40 MPH
08The Paducah radar (KPAH), 124 km away, was scanning. The volume nearest the first event began at 16:28 UTC.
2 flash flood. Local standard time, as filed.
Flooding occurred in several areas on Highway 51 in Puxico. The road was reportedly becoming impassable.
Numerous ditches were overflowing across the northwest part of Butler County, causing street flooding. About two miles southwest of Poplar Bluff, a rainfall amount of 3.1 inches was measured in three hours.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Missouri in 2021Every state in 2021This day in weather historyWarnings in Missouri, August 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: 971626, 971627.