Surface boundaries among a humid air mass, combined with a northwesterly steering flow, resulted in convection over the Cumberland Plateau that moved southeastward into the Tennessee Valley.
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.
Surface boundaries among a humid air mass, combined with a northwesterly steering flow, resulted in convection over the Cumberland Plateau that moved southeastward into the Tennessee Valley.
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 1, 6:34 PM EST, 0 minutes earlier.
AREA FORECAST DISCUSSION...UPDATED National Weather Service Morristown TN 734 PM EDT Wed Jul 1 2020 .UPDATE... FOR 00Z AVIATION. && .SHORT TERM...(Tonight through Thursday)... A low pressure trough was located east of the Appalachians and a weak boundary or front lies across the upper Ohio River valley. Upper level ridging persists over the southern plains and gulf coast with an upper level low along the northeast US coast. The most significant thunderstorm activity is still over the central states and moving southeast along the edge of the upper level ridge. Complex of storms across North Alabama this morning has moved into southern Alabama with more development to the east in central and southern Georgia forming on outflow boundaries. Temperatures at mid afternoon are in the mid to upper 70s where it is cloudy or raining and lower to mid 80s where there has been more sun. There is a lack of convection across the southeast part of the area. Afternoon convection today has been concentrated across southwest Virginia with some activity in central east Tennessee and northeast Tennessee. Expect this activity to be mostly scattered 30 to 40 percent coverage the next few hours and then decrease in the evening. Some areas may pick up a quick half to one inch of rainfall with localized flooding possible especially in urban areas. Tonight with clearing skies and plentiful moisture areas of fog will form. Drier airmass will settle over the region Thursday as boundary to the north slips south of Tennessee or dissipates with temperatures warming into the mid 80s to lower 90s and heat index values reaching the mid 90s central and southern valley. Model guidance showing below 20 pops for entire forecast area but will keep slight chance across extreme southern border counties for diurnal late afternoon and early evening storms. TD .LONG TERM...(Thursday Night through Wednesday)... A summertime pattern is expected throughout the extended period with a mostly weak synoptic wind pattern over the area. Varying PWAT anomalies and 500mb height anomalies do still suggest some variation in precipitation chances and temperatures. The dominant synoptic feature will be a developing and eastward progressing low to our south into next week. Thursday Night through Sunday The period commences with two areas of upper-level troughing over both the north Atlantic coast and the Pacific Northwest. In between the two areas of troughing, a broad upper-level ridge is seen. Across the deep-south, a deep shortwave trough is seen at 500mb, associated with the developing disturbance later in the period. Under this pattern, generally northerly flow aloft will have pulled drier air into the area, evidenced by decreasing 700mb RH values and decreasing 850mb dewpoints. This drier air is positioned north of a surface frontal boundary expected to be just south of Tennessee. The combination of slightly positive height anomalies and drier air keeps PoPs limited diurnally and to higher elevation locations and southernmost areas on Friday. Temperatures near to above normal in the upper 80s to low 90s in most locations seem reasonable for Friday. Heat indexes into the 90s are expected. For Independence Day, a similar pattern is expected with relatively dry air and relatively weak synoptic forcing in place. Model guidance suggests the beginning of development for the surface/upper low but still disagrees on placement for Saturday. Additionally, a 40-50 kt 200mb jet streak centered just to the east of the area could provide some weak upper-level divergence in the southernmost portions of the County Warning Area (CWA). Any development is expected to be isolated with chances further south and over high terrain near the TN/NC border. Similar temperatures/heat indexes are expected. For Sunday, current model guidance is in better agreement for the southerly low pressure system to be near the Florida Panhandle with further strengthening taking place. With strengthening and future northeastern shift in the location of the low, a northern push of moisture is expected. With this push of moisture, shortwave energy, and abundant surface heating, chances for convection look more likely with 40 to 60 PoPs utilized across the area. Generally weak flow aloft will inhibit overall wind shear creation, but overall instability looks sufficient to support convective chances across the entire area. Monday through Wednesday For Monday, broad upper ridging continues towards the north-central portion of the U.S. with an upper trough to the south of the CWA towards the Gulf. The southern low looks to track towards the Carolinas during this time. With continued shortwave energy just to the north and east of the area, chances for typical diurnal summertime convection continue. Chance PoPs were utilized with likely PoPs over higher terrain due to proximity to the low and for orographic lift potential. While not as pronounced, a similar setup is still seen on Tuesday. However, PWAT anomalies increasing to near +0.50 inches per ensemble means do suggest high moisture content, which could help to create more efficient rainfall rates within convection. By Wednesday, a broad upper ridge across much of the U.S. is suggested with surface high pressure dominating. Diurnal chance PoPs were still utilized areas-wide to account for uncertainty for coverage of convection with ample moisture still in place. BW && .AVIATION... 00Z TAF DISCUSSION. The presence of abundant low level moisture across the TN Valley will result in low clouds and fog developing at the TAF sites overnight. The moisture will likely manifest itself as fog at TRI, possibly down to LIFR, and mainly as MVFR to IFR cigs at TYS and CHA. After the fog/clouds lift in the 12-14Z window, VFR conditions will prevail for the rest of the day. DGS && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 71 90 70 92 71 / 40 20 0 20 0 Knoxville McGhee Tyson Airport, TN 69 89 68 91 69 / 40 10 0 10 0 Oak Ridge, TN 69 90 68 91 69 / 40 10 0 10 0 Tri Cities Airport, TN 65 88 64 89 65 / 20 10 0 0 0 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. &&
Hazardous Weather Outlook National Weather Service Morristown TN 338 PM EDT Wed Jul 1 2020 NCZ060-061-TNZ012>018-035>047-067>074-081>087-098>102-VAZ001-002- 005-006-008-021945- 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- 338 PM EDT Wed Jul 1 2020 /238 PM CDT Wed Jul 1 2020/ This Hazardous Weather Outlook is for portions of southwest North Carolina...east Tennessee and southwest Virginia. .DAY ONE...This Afternoon and Tonight Showers and storms late this afternoon will produce heavy rainfall and could cause some areas of localized flooding, especially in area of poor drainage. Additionally, a few storms could become strong with gusty winds being the main threat. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not needed at this time. TD/BW
The Knoxville radar (KMRX), 75 km away, was scanning. The volume nearest the first event began at 23:33 UTC.
3 flash flood. Local standard time, as filed.
Several roads near Jacksboro and Caryville were impassable due to flooding.
Some roads flooded by ponding of water.
Several roadways impassable or washed out.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Tennessee in 2020Every state in 2020This day in weather historyWarnings in Tennessee, July 2020
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: 911234, 911241, 911238.