Another frontal boundary stalls near Knoxville. This helped to focus convection that resulted in localized flash flooding.
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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 MRX wrote it up.
Another frontal boundary stalls near Knoxville. This helped to focus convection that resulted in localized 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 Morristown, TN wrote its last area forecast discussion before the first event at Jul 18, 2:18 PM EST, 1 hour 57 minutes earlier.
AREA FORECAST DISCUSSION National Weather Service Morristown TN 318 PM EDT Sun Jul 18 2021 .SHORT TERM...(Tonight and Monday)... -Convection around the area will trend toward more convection south than north -The threat of strong/severe storms is quite low, while the threat of localized flooding is slightly higher The overall pattern won't change much during the period with a strong ridge aloft to our east and troughing over the NE US. A weak frontal boundary near our southern border will sag further to the south before stalling, but exactly how far south it will make it is still unclear. Right now it looks like it will make it into southern/central parts of our area before stalling, so once this afternoon's convection wanes during the evening hours the focus for better coverage of showers/storms should be across our southern half later tonight into Monday. Instability continues to be limited and shear is weak, and this is expected to be the case again Monday which will keep the chances for any strong/severe storms quite low for the period. However, there continues to be a threat for localized flooding in any areas that receive prolonged or repeated heavy rainfall. This will continue to be mentioned in the HWO. LW .LONG TERM... (Monday night Through Sunday)... Key Messages: 1. Cold front forecast to stall across SE TN/SW NC with increased rain chances Monday night and Tuesday. Beginning Wednesday, isolated to scattered showers and thunderstorms are expected every afternoon. 2. Cooler temperatures forecast Tuesday due to increased clouds and rain. Warm temps with highs in the mid to upper 80s will return on Wednesday and remain through the week. Discussion: In the upper levels, a trough will be over the Northeast with weak troughing extending into the Southeast. A ridge will be over the Central and Western U.S. At the surface, a stalled cold front will linger near SE TN, SW NC and North GA. This boundary will dissipate by Wednesday. Monday night and Tuesday have the highest chance for showers and thunderstorms with POPs of 60 to 80 percent, mainly south of I-40. Beginning Wednesday, isolated to scattered showers and thunderstorms are expected each afternoon as weak high pressure is over the Southeast. Another frontal boundary may bring increased rain chances next weekend. Cooler temperatures forecast Tuesday due to increased clouds and rain. Warm temps with highs in the mid to upper 80s will return on Wednesday and remain through the week. McD && .AVIATION... 18Z TAF DISCUSSION. Will see convection around at times especially early and late in the period, although TRI is likely to be precip free later tonight through the end of the period. Will try to time the best chances for thunder with VCTS and tempo/prob30 groups. Will likely see conditions lower to at least MVFR at times especially in any significant convection, and these lower conditions may become predominant at least for a period late tonight. MVFR cigs are then likely to persist at CHA through the end of the period. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 71 79 69 81 68 / 60 70 70 80 30 Knoxville McGhee Tyson Airport, TN 69 82 69 80 68 / 40 60 50 70 20 Oak Ridge, TN 70 81 67 80 66 / 40 50 50 60 20 Tri Cities Airport, TN 66 83 65 81 63 / 30 40 40 50 10 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. &&
Hazardous Weather Outlook National Weather Service Morristown TN 305 PM EDT Sun Jul 18 2021 NCZ060-061-TNZ012>018-035>047-067>074-081>087-098>102-VAZ001-002- 005-006-008-191915- Cherokee-Clay-Scott-Campbell-Claiborne-Hancock-Hawkins-Sullivan- Johnson-Morgan-Anderson-Union-Grainger-Hamblen-Northwest Cocke- Cocke Smoky Mountains-Northwest Greene-Southeast Greene- Washington-Unicoi-Northwest Carter-Southeast Carter-Roane-Loudon- Knox-Jefferson-Northwest Blount-Blount Smoky Mountains- North Sevier-Sevier Smoky Mountains-Sequatchie-Bledsoe-Rhea-Meigs- McMinn-Northwest Monroe-Southeast Monroe-Marion-Hamilton-Bradley- West Polk-East Polk-Lee-Wise-Russell- 305 PM EDT Sun Jul 18 2021 /205 PM CDT Sun Jul 18 2021/ This Hazardous Weather Outlook is for portions of southwest North Carolina...east Tennessee and southwest Virginia. .DAY ONE...This Afternoon and Tonight Scattered to numerous showers and thunderstorms will continue today into tonight. While a few storms may have brief gusty winds this afternoon, locally heavy rainfall looks to be the primary threat leading to the possibility of localized flooding. .DAYS TWO THROUGH SEVEN...Monday through Saturday Scattered to numerous showers and thunderstorms will continue into Monday, especially south of the I-40 corridor. Locally heavy rainfall will be possible which may lead to localized flooding. .SPOTTER INFORMATION STATEMENT... Spotter activation is not needed at this time.
Special Weather Statement
National Weather Service Morristown TN
420 PM EDT Sun Jul 18 2021
TNZ012-182100-
Scott TN-
420 PM EDT Sun Jul 18 2021
...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN SCOTT COUNTY UNTIL
500 PM EDT...
At 419 PM EDT, Doppler radar was tracking a strong thunderstorm near
Helenwood, or 8 miles southwest of Oneida, moving northeast at 5 mph.
Half inch hail and winds in excess of 40 mph will be possible with
this storm.
Locations impacted include...
Oneida, Huntsville, Helenwood, Winfield, Honey Creek State Park, Big
South Fork National Park and Rugby State Park.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Heavy rainfall is also occurring with this storm, and may lead to
localized flooding due to slow storm movement. Do not drive your
vehicle through flooded roadways.
Frequent lightning is occurring with this storm. Lightning can
strike 10 miles away from a thunderstorm. Seek a safe shelter inside
a building or vehicle.
&&
LAT...LON 3660 8449 3640 8439 3635 8468 3638 8469
3639 8469 3640 8466 3641 8467 3641 8466
3644 8469 3650 8471 3653 8474 3660 8461
TIME...MOT...LOC 2019Z 247DEG 5KT 3647 8464
TDThe Knoxville radar (KMRX), 67 km away, was scanning. The volume nearest the first event began at 21:17 UTC.
1 flash flood. Local standard time, as filed.
Flooding observed on Fox Lonas Road near N Cedar Bluff Road, and also at the intersection of N Cedar Bluff Road and Park West Blvd.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Tennessee in 2021Every state in 2021This day in weather historyWarnings in Tennessee, 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: 976385.