Alert archive / Tennessee / Flash Flood Warnings in 2021

Flash Flood Warning 64, NWS Nashville, TN

September 20, 20214 counties in Tennessee

NWS Nashville, TN issued this flash flood warning at Sep 20, 2021, 4:10 PM CDT for 4 counties in Tennessee. It was in force for 3 hr. 1 report came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Sep 20, 2021, 4:10 PM CDT (21:10 UTC)
Expired: Sep 20, 2021, 6:45 PM CDT
In force: 3 hr
Issued by: NWS Nashville, TN
Area: Storm-based polygon
Flood severity: None

Counties Giles County, TN, Marshall County, TN, Maury County, TN, Williamson County, TN

The radar

The Nashville radar (KOHX), 76 km from the middle of the area, began a volume at 21:12 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

What was reported inside it

Time	Report	Where	Remark
Sep 20, 4:30 PM CDT	FLASH FLOOD	4 W Spring Hill, TN	SEVERAL ROADS IMPASSABLE DUE TO HIGH WATER IN NORTH CENTRAL MAURY COUNTY, INCLUDING SULPHUR SPRINGS BRANCH RD., AND B DODSON RD..

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Nashville Metro, TN (KBNA), launched 12:00Z, 9.2 hours before the alert went out and 63 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 323 J/kg
Mixed-layer CIN: -36 J/kg
Mixed-layer LCL: 758 m above ground
0-6 km bulk shear: 23 kt
0-1 km storm-relative helicity: 149 m²/s²
0-3 km storm-relative helicity: 142 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

032 
WGUS54 KOHX 202110
FFWOHX
TNC055-117-119-187-202345-
/O.NEW.KOHX.FF.W.0064.210920T2110Z-210920T2345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Nashville TN
410 PM CDT Mon Sep 20 2021

The National Weather Service in Nashville has issued a

* Flash Flood Warning for...
  Northern Giles County in middle Tennessee...
  West Central Marshall County in middle Tennessee...
  Eastern Maury County in middle Tennessee...
  South Central Williamson County in middle Tennessee...

* Until 645 PM CDT.

* At 410 PM CDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1.5 and 2.5 inches of 
  rain have fallen. Additional rainfall amounts of 1 to 3 inches are 
  possible in the warned area. Flash flooding is ongoing or expected 
  to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar.

  IMPACT...Flash flooding of small creeks and streams, urban
           areas, highways, streets and underpasses as well as
           other poor drainage and low-lying areas.

* Some locations that will experience flash flooding include...
  Columbia, Spring Hill, Thompson's Station, Lynnville, I-65 East Of 
  Columbia and Culleoka.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood 
deaths occur in vehicles.

In hilly terrain there are hundreds of low water crossings which are 
potentially dangerous in heavy rain. Do not attempt to cross flooded 
roads. Find an alternate route.

&&

LAT...LON 3587 8699 3583 8678 3572 8681 3551 8687
      3531 8693 3533 8715

FLASH FLOOD...RADAR INDICATED

$$

Whitehead

The office that day

Everything else NWS Nashville, TN issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 19, 8:09 PM CDT	River Flood Warning	OHX	Bedford, Marshall	40 hr
Sep 20, 6:25 AM CDT	Areal Flood Advisory	OHX	Dickson, Hickman, Lewis, Maury	2 hr
Sep 20, 7:08 AM CDT	Areal Flood Advisory	OHX	Dickson, Montgomery	112 min
Sep 20, 8:29 AM CDT	Areal Flood Advisory	OHX	Cheatham, Davidson, Hickman, Lewis, Marshall, Maury and 1 more	2 hr
Sep 20, 9:53 AM CDT	Areal Flood Advisory	OHX	Bedford, Davidson, Marshall, Rutherford, Williamson	112 min
Sep 20, 10:10 AM CDT	Areal Flood Advisory	OHX	Dickson, Hickman, Lewis, Maury, Williamson	2 hr
Sep 20, 10:25 AM CDT	Flash Flood Warning	OHX	Dickson, Hickman, Lewis, Maury, Williamson	5 hr
Sep 20, 10:32 AM CDT	Areal Flood Advisory	OHX	Davidson, Robertson, Rutherford, Sumner, Williamson, Wilson	118 min
Sep 20, 10:48 AM CDT	Areal Flood Advisory	OHX	Bedford, Rutherford	4 hr
Sep 20, 11:44 AM CDT	Areal Flood Advisory	OHX	Rutherford, Wilson	3 hr
Sep 20, 12:23 PM CDT	Areal Flood Advisory	OHX	Davidson, Rutherford, Sumner, Williamson, Wilson	3 hr
Sep 20, 1:02 PM CDT	Areal Flood Advisory	OHX	Macon, Sumner, Trousdale, Wilson	3 hr
Sep 20, 3:25 PM CDT	Flash Flood Warning	OHX	Cheatham, Dickson, Hickman, Lewis, Maury, Williamson	5 hr
Sep 20, 3:56 PM CDT	Areal Flood Advisory	OHX	Giles, Marshall, Maury, Williamson	2 hr
Sep 20, 4:26 PM CDT	River Flood Advisory	OHX	Hickman	4 hr
Sep 20, 4:34 PM CDT	River Flood Advisory	OHX	Bedford	11 hr
Sep 20, 5:59 PM CDT	Areal Flood Advisory	OHX	Giles, Lawrence, Lewis, Maury, Wayne	3 hr
Sep 20, 6:51 PM CDT	Flash Flood Warning	OHX	Giles, Lawrence, Lewis, Maury, Wayne	114 min

Nearby

Flash Flood Warnings in Tennessee, 2021 Every flash flood warning in 2021

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.