A weak trough of 500 MB low pressure helped trigger locally heavy rains over western portions of the Tennessee Valley.
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The episode as NWS MRX wrote it up.
A weak trough of 500 MB low pressure helped trigger locally heavy rains over western portions of 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 4, 12:44 PM EST, 31 minutes earlier.
Area Forecast Discussion National Weather Service Morristown TN 144 PM EDT Tue Jul 4 2023 ...New AVIATION... .UPDATE... Issued at 1105 AM EDT Tue Jul 4 2023 Surface observations show fog has mostly dissipated but some low clouds linger across central and northern portions of the area. Low clouds should continue to improve as the sun angle increases and mixing takes place. Overall, the forecast remains on track and only some minor touch-ups to temperature and dewpoints were made to follow most recent observations. Isolated to scattered storms are expected mainly across central and southern areas this afternoon. Surface CAPE generally looks to top out around 1500J/kg based on latest HRRR and HREF guidance, with minimal MLCAPE. Lapse rates are generally lacking as well. A few isolated stronger storms remain possible with gusty winds being the main threat as is typical of summertime diurnal activity. Additionally, PWAT of 1.6-1.8 inches would lead to heavy downpours with any stronger storm as well. Lower moisture availability will keep northeastern portions dry this afternoon. && .SHORT TERM... (Today and tonight) Issued at 254 AM EDT Tue Jul 4 2023 Key Messages: 1. Isolated to scattered showers and storms expected, mainly across south and central areas. Discussion: What remains of the weakening frontal boundary is currently near our southern border. This front will continue to wash out during the period. Models show enough drying across northeastern areas to limit PoPs to less than slight chance so no mention of precipitation there today or tonight. However, moisture increases further south closer to the boundary, and while CAPE values look lower than recent days the HREF shows SBCAPE of around 1000 J/kg or a bit above across portions of the south/central today. Expect scattered to isolated convection today across southern and central areas with greatest coverage south closest to the boundary. Given the more limited CAPE, weaker shear than recent days and DCAPE that looks to be lower than yesterday as well, the probability for severe storms looks low at this time. However, a strong storm with strong gusty winds cannot be ruled out. Enough high clouds are expected to be around to help to limit temperatures to the upper 80s in most valley locations. Tonight models show some weak upper level short wave energy moving in from the west, with mainly isolated weak convection continuing during the night mainly south/central. && .LONG TERM... (Wednesday through Monday) Issued at 254 AM EDT Tue Jul 4 2023 (Wednesday through Monday) Key Messages: 1. Scattered to possibly numerous showers and storms are expected each day with decreased coverage on Saturday. 2. Temperatures will be generally near normal. Wednesday through Friday At the start of the period, a shortwave will be approaching from the west with a stationary front extending through Georgia and Alabama. With increased moisture and low-level convergence, the focus for diurnal convection will be for southern portions of the area. However, vertical ascent and moisture will be sufficient for isolated to scattered coverage area-wide. Overall, the environment will be weakly sheared with MLCAPE generally close to 1,000 J/kg. This will keep potential for strong to severe storms low but typical for this time of year. On Thursday, the upper-level pattern becomes a bit more zonal with embedded shortwaves aloft. The frontal boundary will also weaken but drift further north, making for scattered or better coverage of diurnal convection area-wide but likely more terrain-based. The environment looks fairly similar to Wednesday, meaning fairly low but non-zero chances for stronger storms and/or isolated flooding. By Friday, a broader upper-level trough will advance out of the Great Lakes region, leading to some height falls above the 500mb level. Additionally, the frontal boundary will move even further northward, allowing for better moisture than in previous days. This may produce a better overall convective environment and more widespread coverage. Saturday through Monday The evolution of the pattern is more uncertain later in the period. However, the consensus is for increasing strength in the upper jet closer to the region but with less overall moisture, likely leading to a reduction in coverage of diurnal convection. By Sunday and Monday, moisture return is expected with varying indications of a stronger front and/or trough diving down from the north. This indicates potential for more widespread convection, but the details remain uncertain at this time. Ultimately, the messaging for this period will be kept the same as earlier in the period with repeated showers and storms. && .AVIATION... (18Z TAFS) Issued at 137 PM EDT Tue Jul 4 2023 Isolated to scattered showers and storms will be across the region this afternoon. CHA/TYS are most likely to have vicinity or be impacted by TS. Conditions will remain VFR outside of any stronger downpour that could reduce visibility. Tonight, a little more uncertainty in play regarding fog. Soundings and satellite trends suggest we could continue to see some cloud cover overnight which would not be ideal for fog development. However, a fairly moist airmass is in place with Tds in the upper 60s to mid 70s. Have went with a somewhat persistent forecast from this past morning with prevailing MVFR fog at TRI. Difference being have included a mention of BR at CHA and TYS but not reduced category at this time. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 71 89 70 89 / 30 50 20 60 Knoxville McGhee Tyson Airport, TN 71 88 70 88 / 20 40 20 50 Oak Ridge, TN 69 87 70 87 / 20 40 20 50 Tri Cities Airport, TN 66 86 66 87 / 10 40 20 50 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && SHORT TERM... AVIATION...KRS
Hazardous Weather Outlook National Weather Service Morristown TN 306 AM EDT Tue Jul 4 2023 NCZ060-061-TNZ012>018-035>047-067>074-081>087-098>102-VAZ001-002- 005-006-008-050715- 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- 306 AM EDT Tue Jul 4 2023 /206 AM CDT Tue Jul 4 2023/ This Hazardous Weather Outlook is for portions of southwest North Carolina...east Tennessee and southwest Virginia. .DAY ONE...Today and Tonight There will be isolated to scattered showers and thunderstorms today mainly across the Plateau, southern and central east Tennessee, and southwest North Carolina. A few of these storms may be strong this afternoon producing strong gusty winds and torrential downpours. .DAYS TWO THROUGH SEVEN...Wednesday through Monday Scattered showers and thunderstorms are expected most of the remaining days. A few isolated stronger storms are possible, in addition to localized flooding due to repeated rainfall from slow- moving or training storms. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected.
The Northeast Alabama radar (KHTX), 140 km away, was scanning. The volume nearest the first event began at 18:16 UTC.
2 flash flood. Local standard time, as filed.
Flooding of some homes and garages occurred in Spring City.
Deep water covering roads near the intersection of Lupton Drive and Hixson Pike, near Food City grocery. Car stalled in the water.
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, July 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: 1125851, 1125871.