The combination of abundant tropical moisture and a weak upper level disturbance produced a complex of slow moving thunderstorms across the Concho Valley. As a result, very heavy rain fell in a short period of time on the morning of August 17 and produced flash flooding in San Angelo and Mertzon.
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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 SJT wrote it up.
The combination of abundant tropical moisture and a weak upper level disturbance produced a complex of slow moving thunderstorms across the Concho Valley. As a result, very heavy rain fell in a short period of time on the morning of August 17 and produced flash flooding in San Angelo and Mertzon. Also, radar rainfall estimates were 9 to 10 inches in northwest Tom Green County, just west of OC Fisher Reservoir.
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 San Angelo, TX wrote its last area forecast discussion before the first event at Aug 17, 6:00 AM CST, 1 hour 5 minutes earlier.
Area Forecast Discussion National Weather Service San Angelo TX 700 AM CDT Tue Aug 17 2021 ...New AVIATION... .SHORT TERM... (Today and tonight) Issued at 404 AM CDT Tue Aug 17 2021 Early this morning scattered to numerous showers along with a few lightning strikes are ongoing from the Trans Pecos and Permian Basin eastward into western portions of the Concho Valley. All of this activity is developing ahead of a shortwave trough. The combination of the upper level trough and sufficient instability will lead to scattered to numerous showers and thunderstorms continuing this morning and into the afternoon. In addition, a very moist airmass (precipitable water values of 1.75-2.00 inches per forecast soundings) will lead to the possibility of heavy rainfall which may result in localized flash flooding concerns. Rain chances continue overnight as another disturbance may impact the region. Cloud cover and showers/storms will hold temperatures well below normal this afternoon- mainly in the mid to upper 80s. && .LONG TERM... (Wednesday through Monday) Issued at 438 AM CDT Tue Aug 17 2021 The main concern in the long term will be continued heavy rain with localized areas of flash flooding Wednesday into early Thursday. An upper trough across the Central Plains extending back into north Texas will continue to bring instability and a good chance of rain to the area through Thursday. Precipitable water values remain high, and numerous outflow boundaries will be across the area from convection on Tuesday, so expect thunderstorms to be rather widespread on Wednesday. Rain chances start to decrease Thursday as the upper trough weakens and heads east, but still expecting a decent chance of diurnally driven thunderstorms for Thursday afternoon. A ridge begins to build back in to south and west Texas for Friday, with models trending warmer and drier for the weekend into early next week. && .AVIATION... (12Z TAFS) Issued at 652 AM CDT Tue Aug 17 2021 Showers and thunderstorms continue to develop this morning across the western Concho Valley impacting the KSJT terminal. Expect showers and storms to continue to develop into the afternoon. Will continue with VCSH/VCTS at the terminals and TEMPO TSRA at KSJT this morning. Will likely need to amend the TAFS, however, through the morning and afternoon hours based upon radar trends. && .PRELIMINARY POINT TEMPS/POPS... Abilene 86 69 88 72 / 60 50 60 30 San Angelo 84 69 88 72 / 70 50 60 30 Junction 87 71 91 73 / 60 40 50 30 Brownwood 87 71 90 74 / 60 50 60 30 Sweetwater 84 69 88 72 / 60 40 60 30 Ozona 83 69 85 71 / 70 50 50 20 && .SJT WATCHES/WARNINGS/ADVISORIES... None. && SHORT TERM...42 LONG TERM....08 AVIATION...42
Hazardous Weather Outlook National Weather Service San Angelo TX 342 AM CDT Tue Aug 17 2021 TXZ049-054-064>066-071>073-076>078-098-099-113-114-127-128-139- 140-154-155-168>170-180845- Fisher-Nolan-Sterling-Coke-Runnels-Irion-Tom Green-Concho- Crockett-Schleicher-Sutton-Haskell-Throckmorton-Jones-Shackelford- Taylor-Callahan-Coleman-Brown-McCulloch-San Saba-Menard-Kimble- Mason- 342 AM CDT Tue Aug 17 2021 This Hazardous Weather Outlook is for portions of west central Texas. .DAY ONE...Today and Tonight Scattered showers and thunderstorms are possible today and tonight. The main hazards will be heavy rainfall which could lead to localized flooding and dangerous lightning. .DAYS TWO THROUGH SEVEN...Wednesday through Monday Scattered showers and thunderstorms are again possible on Wednesday. The main hazards will be heavy rainfall which could lead to localized flooding and dangerous lightning. .SPOTTER INFORMATION STATEMENT... Spotter activation is not anticipated at this time.
The San Angelo radar (KSJT), 7 km away, was scanning. The volume nearest the first event began at 13:07 UTC.
5 flash flood. Local standard time, as filed.
The San Angelo Police Department reported several streets flooded across San Angelo along with several stranded vehicles.
The Tom Green Sheriffs Office reported flooded roads in Arden.
The Tom Green Sheriffs Office reported widespread flooding along Farm to Market Road 2288.
A social media post indicated several streets and low water crossings flooded in Mertzon.
A National Weather Service Employee reported that South Jackson is blocked off due to flooding. In addition, a video from Facebook showed a high water rescue at the same location.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Texas in 2021Every state in 2021This day in weather historyWarnings in Texas, 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: 981238, 981239, 981240, 981241, 981242.