Thanks to a stationary boundary draped southwest to northeast across the TN and Mid-MS Valley, several waves of moderate to heavy rainfall occurred on September 13, 2020. While the heaviest rainfall totals remained to the north of the Hydrologic Service Area across portions of Western Tennessee, portions of Northwest Alabama were on the southern tip of the heavy rainfall received that day.
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 HUN wrote it up.
Thanks to a stationary boundary draped southwest to northeast across the TN and Mid-MS Valley, several waves of moderate to heavy rainfall occurred on September 13, 2020. While the heaviest rainfall totals remained to the north of the Hydrologic Service Area across portions of Western Tennessee, portions of Northwest Alabama were on the southern tip of the heavy rainfall received that day. Nearly continuous rainfall occurred for 5-7 hours across these locations, leading to several instances of nuisance and flash flooding. Storm total rainfall amounts ranged from 4-6 on this day.
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 Huntsville, AL wrote its last area forecast discussion before the first event at Sep 13, 8:39 AM CST, 2 hours 51 minutes earlier.
Area Forecast Discussion National Weather Service Huntsville AL 939 AM CDT Sun Sep 13 2020 .NEAR TERM...(Rest of Today) Issued at 940 AM CDT Sun Sep 13 2020 Surface analysis this morning continues to feature a weak convergence boundary stretching from the Great Lakes region through the Lower MS Valley. This boundary was a focus for showers and a few storms across NW AL overnight and continues to be a focus for lingering showering activity this morning. Rainfall across NW AL through S. Middle TN has shown a tight gradient. While only a Trace was picked up at KMSL, 3 to 4 inches were reported by CocoRaHS observers in Northern Lauderdale Co. As such, will maintain the Flash Flood Watch at least through this afternoon to account for additional diurnal convection. For the update - will continue to showcase rain chances as a fairly tight gradient from the NW to SE. The aforementioned boundary is expected to dip to the south later this afternoon, but break up in coverage. Temps outside of the shower/storm activity will be a little uncomfortable with temps in the mid/upper 80s and dew points in the mid 70s. .SHORT TERM...(Tonight through Tuesday night) Issued at 505 AM CDT Sun Sep 13 2020 A few lingering showers will be possible across the TN Valley early this evening, before diminishing within a few hours of sunset. However, additional convection may develop along the remnant low- level boundary (which will likely extend across TN) early Monday morning and shift southwestward, as steering currents assume a light northerly component. Although weak flow aloft will continue on Monday with the subtropical ridge positioned across the TN Valley, low- level east-northeasterly winds will strengthen considerably as TC Sally drifts northwestward into the northern Gulf of Mexico. This could allow a few afternoon showers and thunderstorms developing across the higher terrain to the north/east of Huntsville to shift west-southwestward. However, based on the amount of drying aloft observed in forecast soundings, we expect this activity to remain scattered in coverage and dissipate within a few hours of sunset Monday evening. During the period from Monday night-Tuesday night, the subtropical ridge (initially centered across our region) will build eastward, eventually becoming established across the southern FL peninsula. Deep-layer southeasterly flow will steadily strengthen in the gradient between the ridge to our southeast and TC Sally, which is predicted by NHC to be lifting north-northwestward across eastern LA/southern MS during this period. The rapid northwestward return of tropical moisture on Tuesday will support scattered-numerous showers and thunderstorms, which should be greatest in coverage across the southwestern portion of the CWFA where the lingering influence from drier air aloft will be less. By Tuesday night, increasing synoptic scale ascent coupled with warm/moist advection should result in a northward expanding area of rain and embedded convective showers by sunrise on Wednesday. High temperatures will remain in the m-u 80s on Monday, but should fall into the l-m 80s region-wide on Tuesday as tropical moisture returns to the region. Lows will generally be in the m-u 60s, but could fall into the lower 60s early Tuesday morning across our TN counties. .LONG TERM...(Wednesday through Saturday) Issued at 505 AM CDT Sun Sep 13 2020 The main story for the long term period will be heavy rain in upwards of 2 to 4 inches with locally higher amounts associated with Tropical Storm Sally as it moves across the Tennessee Valley. The current forecast track from the NHC has the center of the circulation moving through Alabama starting late Wednesday and into Thursday. However, outer bands of showers and storms will begin to impact the local area starting Wednesday morning. As expected with tropical airmasses, PWATs around 2 inches will result in very efficient rainfall that may result in flash flooding. While a flash flood watch may be needed at a future time, it is not being considered with this forecast package given the event is still 4 days out. Similar to Hurricane Laura a few weeks ago, tropical tornadoes are once again possible, but this will largely depend on the track and intensity of Sally as it moves inland later this week. On Thursday night, a cold front dropping in from the Plains will help eject the remnants of Sally to our east. The overnight model runs still show a lack of agreement on when exactly this front arrives with the GFS the earliest of the global models, clearing out the rain by Thursday night whereas the ECMWF has the front approximately 12 hrs behind. Either way, cooler and drier air advects in from the northwest by Friday night. A beautiful weekend is in store with highs around 80 and dewpoints in the upper 50s to lower 60s. && .AVIATION...(For the 12Z TAFS through 12Z Monday morning) Issued at 654 AM CDT Sun Sep 13 2020 SHRA/TSRA will continue to impact locations invof a stalled low- level convergence axis draped across NW AL and southern Middle TN this morning. It appears as if the bulk of the convection in our region will be closely tied to this feature, and for this reason we have only included -SHRA in a TEMPO group for the MSL terminal. However, a broken deck of low stratus clouds could periodically impact both airport locations through 16Z, and this has been included in TEMPO groups as well. Latest model guidance suggests that the overall coverage of precipitation will diminish this aftn, as environmental conditions become less favorable for convection. Thus, we will indicate VFR conditions for the remainder of the TAF period, with few stratocu beneath sct-bkn mid and high clouds. Sfc winds will remain from the SE at 5-10 knots today, but will shift to NE at similar speeds early this evening. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...Flash Flood Watch until 7 PM CDT this evening for ALZ001>005. TN...Flash Flood Watch until 7 PM CDT this evening for TNZ076-096. && NEAR TERM...Barron SHORT TERM...70/DD LONG TERM...GH AVIATION...70/DD For more information please visit our website at weather.gov/huntsville.
Hazardous Weather Outlook National Weather Service Huntsville AL 601 AM CDT Sun Sep 13 2020 ALZ001>005-TNZ076-096-141130- Lauderdale-Colbert-Franklin AL-Lawrence-Limestone-Moore-Lincoln- 601 AM CDT Sun Sep 13 2020 ...FLASH FLOOD WATCH IN EFFECT THROUGH THIS EVENING... This Hazardous Weather Outlook is for north central Alabama, northwest Alabama and southern middle Tennessee. .DAY ONE...Today and tonight. Please listen to NOAA Weather Radio or go to weather.gov on the Internet for more information about the following hazards. Flash Flood Watch. Scattered to numerous showers and thunderstorms will continue across the outlook area today. The greatest concentration of this activity will occur during the morning hours and in the vicinity of a frontal boundary stalled across northwest Alabama and southern Middle Tennessee. Due to the potential for several consecutive rounds of moderate to heavy rainfall in this region, a Flash Flood Watch has been issued through 7 PM CDT. The threat for both thunderstorms and locally heavy rainfall will diminish around sunset this evening. .DAYS TWO THROUGH SEVEN...Monday through Saturday. Scattered to numerous showers and thunderstorms will continue for much of the upcoming work week, with the greatest coverage expected to be on Wednesday and Thursday, when the remnant circulation of Tropical Cyclone Sally will shift northeastward through the region. There is an increasing risk for locally heavy rainfall and flooding across the Tennessee Valley during this period, and a few strong storms will be possible as well. .SPOTTER INFORMATION STATEMENT... Formal activation of storm spotters and emergency management personnel is not anticipated at this time. However, timely reports of flooding will be greatly appreciated. Please relay any information about observed severe weather to the NWS while following all local, state, and CDC guidelines. ALZ006>010-016-TNZ097-141130- Madison-Morgan-Marshall-Jackson-DeKalb-Cullman-Franklin TN- 601 AM CDT Sun Sep 13 2020 This Hazardous Weather Outlook is for north central Alabama, northeast Alabama and southern middle Tennessee. .DAY ONE...Today and tonight. Scattered to numerous showers and thunderstorms will continue across the outlook area today. However, the greatest concentration of this activity will occur during the morning hours and in the vicinity of a frontal boundary stalled across northwest Alabama and southern Middle Tennessee. The threat for both thunderstorms and locally heavy rainfall will diminish around sunset this evening. .DAYS TWO THROUGH SEVEN...Monday through Saturday. Scattered to numerous showers and thunderstorms will continue for much of the upcoming work week, with the greatest coverage expected to be on Wednesday and Thursday, when the remnant circulation of Tropical Cyclone Sally will shift northeastward through the region. There is an increasing risk for locally heavy rainfall and flooding across the Tennessee Valley during this period, and a few strong storms will be possible as well. .SPOTTER INFORMATION STATEMENT... Activation of storm spotters and emergency management personnel is not anticipated at this time. 70/DD
The Columbus AFB radar (KGWX), 121 km away, was scanning. The volume nearest the first event began at 17:30 UTC.
5 flash flood, 1 heavy rain. Local standard time, as filed.
Portions of Heathrow Drive flooded. No depth of water given.
Three northbound lanes of Cloverdale Road reported flooded. Water of unknown depth.
Water moving rapidly over the road at the intersection of Highway 72 W and Shop Loop Road.
Several inches of water over driveway near carport and getting close to entering the house at this location on Frey Avenue.
Up to 12 inches of water reported over the road at the intersection of E 1st Street and N Cave Street near Deshler Football Stadium.
Water three to four inches deep was reported in the Walmart Parking lot at this location.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Alabama in 2020Every state in 2020This day in weather historyWarnings in Alabama, September 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: 921091, 921092, 921094, 921095, 921096, 921113.