A midlevel shortwave trough plus a very moist airmass combined to produce an isolated severe thunderstorm over Knox County in East Tennessee, leading to several reports of thunderstorm driven wind damage.
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 MRX wrote it up.
A midlevel shortwave trough plus a very moist airmass combined to produce an isolated severe thunderstorm over Knox County in East Tennessee, leading to several reports of thunderstorm driven wind damage.
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 May 20, 2:44 PM EST, 3 hours 2 minutes earlier. Its key messages:
Area Forecast Discussion...UPDATED National Weather Service Morristown TN 344 PM EDT Wed May 20 2026 ...New DISCUSSION, AVIATION... .KEY MESSAGES... Updated at 343 PM EDT Wed May 20 2026 - Rain chances increase this afternoon and evening, with continued high rain chances through the first half of next week. - Organized severe storms appear unlikely during this forecast period, but the primary threats with storms each day will be lightning, locally heavy rainfall, and some gusty winds. && .DISCUSSION... Issued at 343 PM EDT Wed May 20 2026 Convection has gotten off to an early start today in an increasingly moist air mass, developing in Middle TN and the Plateau, which is an area of higher surface CAPE values around 1500 J/kg and surface confluence. There is little to no shear to help sustain or organize these storms, so they will mainly be driven by outflow boundaries, terrain, and convergence zones. Expect that coverage will increase in the central and southern TN Valley over the next few hours. The main hazards will be lightning and some locally heavy rainfall that could cause minor flooding issues. Isolated to scattered showers are expected to persist through the night due to the moisture rich environment, the presence of a midlevel shortwave trough, and some upper divergence. A front in the OH Valley region today will move southward and be near our northwest border by Thursday morning. This will act as a focus for convergence and convective development Thursday. PoPs will be categorical across the entire area, with a chance of thunderstorms. Instability and shear will be lacking for any organized severe threat, although some gusty downburts winds and locally heavy rainfall will be possible. A strengthening southerly flow ahead of a low over AR lifts the aforementioned boundary northward on Friday, putting our area into the warm sector in the afternoon. LREF joint probabilities of CAPE > 1000 J/kg and shear > 25 kt are around 30% across the area, and near 40% in our southern sections where clouds may scatter enough to enhance afternoon heating. A few strong to severe storms cannot be ruled out for Friday, but the chance remains low. A deep SW flow persists through the weekend and early next week, with broad troughing over the central US. Disturbances ejecting from this broad trough will bring several rounds of enhanced rain chances through early next week, but the timing of these disturbances remains higly uncertain. Overall, the pattern favors continued high rain chances each day. The primary impacts will be lightning and locally heavy rainfall. QPF through the next 7 days will vary widely across our area, depending on which areas see repeated showers and storms over numerous days. Generally speaking, 1-3" of rain is forecast through the period. && .AVIATION... (18Z TAFS) Issued at 343 PM EDT Wed May 20 2026 Showers and storms will be near CHA over the next few hours, and may bring TS with MVFR/ vis/cigs. This activity may spread toward TYS later in the evening, and potentially to TRI later in the night. With a moist boundary layer, low clouds at MVFR levels are expected to form and persist into tomorrow morning, but this may be dependent on whether showers pass over the terminals this evening. Confidence of this happening is high at CHA, medium at TYS, and low at TRI. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 66 83 65 83 / 70 60 90 90 Knoxville McGhee Tyson Airport, TN 66 81 64 82 / 70 90 50 90 Oak Ridge, TN 64 81 63 81 / 70 80 60 90 Tri Cities Airport, TN 62 79 61 80 / 70 90 50 80 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && DISCUSSION...DGS AVIATION...DGS
Hazardous Weather Outlook...UPDATED National Weather Service Morristown TN 256 PM EDT Wed May 20 2026 NCZ060-061-TNZ012>018-035>047-067>074-081>087-098>102-VAZ001-002- 005-006-008-211900- Cherokee-Clay-Scott TN-Campbell-Claiborne-Hancock-Hawkins- Sullivan-Johnson-Morgan-Anderson-Union-Grainger-Hamblen- Northwest Cocke-Cocke Smoky Mountains-Northwest Greene- Southeast Greene-Washington TN-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-Scott VA-Russell-Washington VA- 256 PM EDT Wed May 20 2026 /156 PM CDT Wed May 20 2026/ This Hazardous Weather Outlook is for portions of southwest North Carolina...east Tennessee and southwest Virginia. .DAY ONE...This Afternoon and Tonight A few stronger storms this afternoon and evening may be capable of producing strong wind gusts and locally heavy rainfall. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday The probability for widespread hazardous weather is low. .SPOTTER INFORMATION STATEMENT... Spotter activation is not needed at this time.
Special Weather Statement
National Weather Service Morristown TN
615 PM EDT Wed May 20 2026
TNZ038>040-042-070-202300-
Jefferson TN-Hamblen TN-Northwest Greene TN-Northwest Cocke TN-
Grainger TN-
615 PM EDT Wed May 20 2026
...A STRONG THUNDERSTORM WILL IMPACT EASTERN JEFFERSON...NORTHWESTERN
COCKE...WEST CENTRAL GREENE...EAST CENTRAL GRAINGER AND HAMBLEN
COUNTIES THROUGH 700 PM EDT...
At 615 PM EDT, Doppler radar was tracking a strong thunderstorm near
Dandridge, moving northeast at 15 mph.
HAZARD...Wind gusts up to 40 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
Locations impacted include...
Morristown, Jefferson City, Dandridge, White Pine, Baneberry, Panther
Creek State Park, Alpha, and Lowland.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 3595 8332 3602 8352 3631 8340 3615 8306
TIME...MOT...LOC 2215Z 208DEG 13KT 3606 8338
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...40 MPHSpecial Weather Statement
National Weather Service Morristown TN
620 PM EDT Wed May 20 2026
TNZ036-067>069-071-202300-
Anderson TN-Roane TN-Loudon TN-Knox TN-NW Blount TN-
620 PM EDT Wed May 20 2026
...A STRONG THUNDERSTORM WILL IMPACT LOUDON...SOUTHWESTERN KNOX...
SOUTH CENTRAL ANDERSON...NORTHWESTERN BLOUNT AND NORTHEASTERN ROANE
COUNTIES THROUGH 700 PM EDT...
At 620 PM EDT, Doppler radar was tracking a strong thunderstorm over
Loudon, moving northeast at 15 mph.
HAZARD...Wind gusts up to 40 mph and pea size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor hail damage to vegetation is
possible.
Locations impacted include...
Knoxville, Oak Ridge, Lenoir City, Loudon, Farragut, Oliver Springs,
Louisville, Philadelphia, Bradbury, and Tellico Village.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 3564 8429 3565 8429 3566 8431 3567 8432
3566 8433 3567 8435 3566 8435 3565 8436
3571 8446 3603 8433 3588 8403
TIME...MOT...LOC 2220Z 209DEG 12KT 3571 8435
MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPHSpecial Weather Statement
National Weather Service Morristown TN
621 PM EDT Wed May 20 2026
TNZ069-071-073-202300-
Knox TN-North Sevier TN-NW Blount TN-
621 PM EDT Wed May 20 2026
...A STRONG THUNDERSTORM WILL IMPACT EASTERN KNOX...NORTH CENTRAL
BLOUNT AND NORTHWESTERN SEVIER COUNTIES THROUGH 700 PM EDT...
At 621 PM EDT, Doppler radar was tracking a strong thunderstorm over
Rockford, or near Alcoa, moving northeast at 15 mph.
HAZARD...Wind gusts up to 40 mph and pea size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor hail damage to vegetation is
possible.
Locations impacted include...
Knoxville, Alcoa, Louisville, Rockford, Eagleton Village,
Maloneyville, Lake Forest, Mascot, Seymour, and Kimberlin Heights.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 3577 8386 3584 8405 3614 8390 3600 8361
TIME...MOT...LOC 2221Z 209DEG 12KT 3586 8391
MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPHThe Knoxville radar (KMRX), 53 km away, was scanning. The volume nearest the first event began at 22:47 UTC.
5 thunderstorm wind. Local standard time, as filed.
A large tree was felled by severe thunderstorm winds and blocked the whole road.
Tree felled by severe thunderstorm winds partially blocked the eastbound lanes of a local road.
A large tree was felled by severe thunderstorm wind gusts and partially blocked a roadway.
A large tree was knocked over by thunderstorm winds, hanging over a local road on top of powerlines.
A large tree was felled by severe thunderstorm wind gusts and blocked the entirety of a local road.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Tennessee in 2026Every state in 2026This day in weather historyWarnings in Tennessee, May 2026
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: 1330484, 1330485, 1330486, 1330487, 1330488.