Marginally supportive shear and plenty of CAPE combine to produce numerous severe thunderstorms that grew upscale into a mesoscale convective system. This MCS progressed from west to east across eastern Tennessee, bringing numerous reports of damaging winds and isolated flash flooding.
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.
Marginally supportive shear and plenty of CAPE combine to produce numerous severe thunderstorms that grew upscale into a mesoscale convective system. This MCS progressed from west to east across eastern Tennessee, bringing numerous reports of damaging winds and isolated 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 Aug 12, 11:38 AM CST, 14 minutes earlier.
Area Forecast Discussion National Weather Service Morristown TN 138 PM EDT Sat Aug 12 2023 ...New SHORT TERM, LONG TERM... .UPDATE... Issued at 1059 AM EDT Sat Aug 12 2023 Current satellite and surface observations show an MCS with strong to severe thunderstorms across northwestern TN through west/central KY moving east-southeastward through the afternoon. The 12z suite of CAMs have initialized poorly and do not adequately show the near-storm environment across West TN and West KY. These storms and outflow will move into a very unstable environment across the Tennessee Valley and Southern Appalachians this afternoon with MLCAPE near or above 3000 J/Kg resulting in DCAPE of around 1200 J/Kg. Effective bulk shear of 30 to 35 kt is sufficient for maintaining thunderstorm organization. This thermodynamic environment will be very favorable for damaging wind gusts with the strongest thunderstorms this afternoon. Current timing of maximum thunderstorm coverage is expected to be between around 18z and 23z this afternoon. JB && .SHORT TERM... (This evening through Sunday) Issued at 114 PM EDT Sat Aug 12 2023 Key Messages: 1. Hot with strong to severe thunderstorms this afternoon. 2. Hot again on Sunday with a chance of afternoon thunderstorms, though expected less coverage than today. Discussion: The MCS moving eastward across the Tennessee Valley this afternoon will impact us over the next several hours. As it encounters a very moist, unstable boundary layer, this convection will continue to be strong to severe. Current SPC/RAP mesoanalysis indicates MLCAPE of 3000 J/Kg which should increase slightly over the next couple of hours with DCAPE values of 900 to 1200 across the region. Damaging winds will be the primary risk, but some severe hail and a low risk of a brief, spin up tornado will be possible. We have observed some bowing segments with potential QLCS tornadoes that have been warned just east of Nashville, and with 0-1 km shear of about 20 kt, that risk will remain as the MCS moves eastward into our area. Convection should exit the area by around 23z this evening with some lingering clouds and fog formation overnight. The shortwave that produced today's convection will be east of the area with some shortwave ridging working to limit convective coverage on Sunday afternoon. Because of this ridging, we will have lower instability with RAP forecast 2000 J/Kg MLCAPE and lower mid-level lapse rates. However, some convective initiation will still be possible along any lingering outflow boundaries and across the higher elevations. Thunderstorm chances may increase into Sunday night as another shortwave dives southeastward towards the region. && .LONG TERM... (Sunday night through next Saturday) Issued at 114 PM EDT Sat Aug 12 2023 Key Messages: 1. Additional showers and storms are possible at times Monday and some storms may become strong to severe. Main threats will be damaging winds and hail. 2. Heat indices could approach 100 degrees for central and southern portions of the area at times Sunday and Monday. 3. Cooler and drier conditions expected Tuesday through Thursday. Discussion: The main focus for the extended period will be Monday and Monday night as another anomalous shortwave tracks into the Ohio Valley and eastward. The positively tilted shortwave will result in H5 flow amplifying upwards of 50-60kts, with southwesterly H85 winds increasing to roughly 30-40kts per the latest NAM model run. Some initial convection may be possible across northern portions of the area where upper level diffluence occurs ahead the shortwave Monday morning/mid-day. Quite honestly there still remains a bit of uncertainty with timing and confidence in severe weather chances for this time period. Most recent model solutions from the NAM3K and HRRR differ significantly on the placement of this early day convection, with the HRRR being most bullish on a potential MCS progressing near the TN/KY/VA border. Soundings ahead of the MCS show an unusually unstable environment for morning hours with MLCAPE nearing 2000J/kg. If a scenario as such pans out, some strong to severe storms may be possible early morning mid-day across northern portions of the area, damaging winds and hail being the primary concerns. Storms should clear out for the afternoon with muggy and hot conditions expected. Heat indices could approach 100 degrees for portions of the southern and central Tennessee Valley. A cold front is anticipated to approach the area bringing additional storm chances late Monday potentially into early Tuesday morning. Timing will play an important role in the severe weather chances as slower timing could lead to increasingly diminishing instability. NAM soundings currently continue to show MUCAPE persisting between 1000- 2000 J/kg ahead of the convection. Again, winds and hail will be the main threats. For this Monday timeframe, isolated flooding cannot be ruled out for areas that see multiple rounds of showers and storms as well. Some light lingering activity may persist early/mid-Tuesday with wrap around moisture but the general trend for the remainder of the week will be drier with temperatures slightly below normal. An additional trough will dig south from the Great Lakes region late week but plenty of model discrepancies lead to uncertainty on the potential of returning PoP chances at the end of the extended. && .AVIATION... (18Z TAFS) Issued at 103 PM EDT Sat Aug 12 2023 A line of strong to severe thunderstorms will impact terminals this afternoon with these storms expected to exit the area by around 23z. Fog potential will exist overnight with a very moist boundary layer environment and evening rainfall accumulation. Additional thunderstorm potential again on Sunday afternoon late in the period where we've included a prob30 for tsra. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 93 73 93 75 / 50 30 40 10 Knoxville McGhee Tyson Airport, TN 90 73 89 74 / 60 30 40 20 Oak Ridge, TN 89 72 89 73 / 50 40 50 20 Tri Cities Airport, TN 87 70 85 70 / 50 40 40 20 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && SHORT TERM...JB LONG TERM....KRS AVIATION...JB
Hazardous Weather Outlook National Weather Service Morristown TN 1059 AM EDT Sat Aug 12 2023 NCZ060-061-TNZ012>018-035>047-067>074-081>087-098>102-VAZ001-002- 005-006-008-131500- 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- 1059 AM EDT Sat Aug 12 2023 /959 AM CDT Sat Aug 12 2023/ This Hazardous Weather Outlook is for portions of southwest North Carolina...east Tennessee and southwest Virginia. .DAY ONE...Today and Tonight Severe thunderstorms will be possible this afternoon. Damaging winds will be the main risk with a low risk of hail, and a very low risk of a brief spin-up tornado. Heat index values are expected to be around 100 to 105 in the southern Tennessee Valley today near Chattanooga. Practice heat safety this afternoon. .DAYS TWO THROUGH SEVEN...Sunday through Friday An active period continues into Sunday and Monday with multiple rounds of storms possible. Strong to severe storms are possible each of these days. Also, hot conditions are expected with many central and southern TN Valley locations seeing heat indices close to 100 degrees. .SPOTTER INFORMATION STATEMENT... Spotter reports may be needed this afternoon through Monday for severe thunderstorms.
Special Weather Statement
National Weather Service Morristown TN
114 PM EDT Sat Aug 12 2023
TNZ081-098-099-121800-
Sequatchie TN-Marion TN-Hamilton TN-
114 PM EDT Sat Aug 12 2023
...A STRONG THUNDERSTORM WILL IMPACT SOUTHERN SEQUATCHIE...
SOUTHEASTERN MARION AND SOUTHWESTERN HAMILTON COUNTIES THROUGH 200 PM
EDT/100 PM CDT/...
At 114 PM EDT/1214 PM CDT/, Doppler radar was tracking a strong
thunderstorm 7 miles northwest of Kimball, or 8 miles northwest of
Jasper, moving east at 35 mph.
HAZARD...Wind gusts up to 50 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...
Chattanooga, Jasper, Soddy-Daisy, Signal Mountain, South Pittsburg,
Walden, Whitwell, Kimball, Ridgeside, and Fairmount.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.
A Severe Thunderstorm Watch remains in effect until 700 PM EDT/600 PM
CDT/ for east Tennessee.
&&
LAT...LON 3499 8573 3521 8571 3524 8520 3499 8522
3498 8550
TIME...MOT...LOC 1714Z 274DEG 28KT 3513 8575
MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH
KRSSpecial Weather Statement
National Weather Service Morristown TN
136 PM EDT Sat Aug 12 2023
TNZ012>014-036-037-121815-
Anderson TN-Claiborne TN-Scott TN-Union TN-Campbell TN-
136 PM EDT Sat Aug 12 2023
...STRONG THUNDERSTORMS WILL IMPACT NORTHWESTERN CLAIBORNE...
ANDERSON...CAMPBELL...EASTERN SCOTT AND WESTERN UNION COUNTIES
THROUGH 215 PM EDT...
At 136 PM EDT, Doppler radar was tracking a cluster of strong
thunderstorms along a line extending from 6 miles south of Zion Hill
to near Jacksboro to 7 miles north of Oliver Springs. Movement was
east at 25 mph.
HAZARD...Wind gusts up to 50 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...
Clinton, La Follette, Jacksboro, Jellico, Caryville, Rocky Top,
Norris, Norris Dam State Park, Elk Valley, and Smokey Junction.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
A Severe Thunderstorm Watch remains in effect until 700 PM EDT for
east Tennessee.
&&
LAT...LON 3659 8389 3636 8388 3619 8394 3609 8406
3612 8442 3614 8445 3616 8444 3618 8446
3638 8435 3659 8433
TIME...MOT...LOC 1736Z 268DEG 20KT 3652 8426 3636 8426 3614 8436
MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH
DieganThe Northeast Alabama radar (KHTX), 53 km away, was scanning. The volume nearest the first event began at 17:53 UTC.
35 thunderstorm wind, 2 flash flood, 1 hail. Local standard time, as filed.
Multiple trees blown down by severe thunderstorm winds across the county.
Several trees blown down by powerful thunderstorm winds.
A few trees blown down by severe thunderstorm wind gusts.
A few trees blown down by severe thunderstorm wind gusts.
A few trees blown down by severe thunderstorm wind gusts.
Several trees blown down by severe thunderstorm wind gusts.
Several trees blown down by severe thunderstorm winds.
Multiple trees and powerlines blown down by severe thunderstorm gusts.
Several trees blown down by powerful thunderstorm winds.
Large tree blown down by thunderstorm winds near intersection.
Several trees blown down by severe thunderstorm wind gusts.
Large tree blown down by thunderstorm winds blocking lanes on road.
A few trees blown down by severe thunderstorm winds.
Several trees blown down by thunderstorm winds.
Multiple trees were blown down by severe thunderstorm wind gusts.
Several trees were blown down across the local area by severe thunderstorm winds.
A few trees were blown down by severe thunderstorm winds.
Several trees blown down by severe thunderstorm wind gusts.
Multiple trees blown down by powerful wind gusts.
A few trees blown down by powerful thunderstorm winds.
Several trees were blown down by severe thunderstorm winds.
A large tree was blown down by severe thunderstorm wind gusts and blocked traffic on roadway.
A large tree was blown down by severe thunderstorm wind gusts and blocked traffic. In addition, several other trees nearby were also felled by the winds.
A large tree was blown down by severe winds alongside the intersection of two local roads.
Several trees were blown down along the roadways by severe thunderstorm wind gusts.
Severe wind gust was recorded on a home weather station.
Multiple trees were blown down by severe thunderstorm wind gusts.
A large tree was blown down by severe thunderstorm winds and blocked Skyview Drive.
Multiple trees were blown down by severe thunderstorm gusts.
A large tree was blown down by severe thunderstorm winds and blocked a lane of traffic on local road.
A few trees across the area were blown down by powerful thunderstorm winds.
Portions of Wolf Creek Road flooded.
Several trees and powerlines were blown down by severe thunderstorm winds.
Photos of flooded roads.
A few trees were blown down by powerful thunderstorm gusts.
Several large trees were felled by thunderstorm winds and blocked traffic on local road.
Several trees, and a sign, were blown over by severe thunderstorm winds.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Tennessee in 2023Every state in 2023This day in weather historyWarnings in Tennessee, August 2023
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: 1121359, 1121360, 1121362, 1121364, 1121365, 1121367, 1121379, 1121381, 1121383, 1121387, 1121393, 1121397, 1121395, 1121356, 1121399, 1121414, 1121415, 1121404, 1121400, 1121401, 1121403, 1121405, 1121406, 1121407, 1121425, 1121408, 1121412, 1121411, 1121413, 1121424, 1121417, 1121418, 1133802, 1121419, 1133803, 1121420, 1121422, 1121423.