Alert archive / Tennessee / Flash Flood Warnings in 2021

Flash Flood Warning 42, NWS Morristown, TN

September 20, 2021Hamilton County, Marion County, Tennessee

NWS Morristown, TN issued this flash flood warning at Sep 20, 2021, 2:53 PM EDT for Hamilton County, Marion County, Tennessee. It was in force for 4 hr. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
Sep 20, 2021, 2:53 PM EDT (18:53 UTC)
Expired
Sep 20, 2021, 7:00 PM EDT
In force
4 hr
Issued by
NWS Morristown, TN
Area
Storm-based polygon
Flood severity
None

Counties Hamilton County, TN, Marion County, TN

The radar

The Northeast Alabama radar (KHTX), 62 km from the middle of the area, began a volume at 18:53 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.

The nearest sounding before it

Nashville Metro, TN (KBNA), launched 12:00Z, 6.9 hours before the alert went out and 152 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-pSkew-T log-p diagram, Nashville Metro, TN at 12:00Z on 2021-09-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 323 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Nashville Metro, TN at 12:00Z on 2021-09-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 149 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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.

818 
WGUS54 KMRX 201853
FFWMRX
TNC065-115-202300-
/O.NEW.KMRX.FF.W.0042.210920T1853Z-210920T2300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Morristown TN
253 PM EDT Mon Sep 20 2021

The National Weather Service in Morristown has issued a

* Flash Flood Warning for...
  Southwestern Hamilton County in east Tennessee...
  Marion County in east Tennessee...

* Until 700 PM EDT /600 PM CDT/.

* At 253 PM EDT /153 PM CDT/, Doppler radar indicated showers 
  producing additional moderate to heavy rain across the warned 
  area. Between 0.5 and 1 inch of rain has fallen today with in 
  excess of 4 inches during the past 24 hours. Additional rainfall 
  amounts of 0.5 to 1.5 inches are possible in the warned area.

The additional rainfall over already saturated soils will likely 
cause flash flooding. Local law enforcement continued to report some 
flooded roadways in Marion and southern Hamilton counties.

  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...
  Chattanooga, Jasper, Signal Mountain, South Pittsburg, Walden, 
  Whitwell, Kimball, Ridgeside, Fairmount, Harrison, Red Bank, 
  Collegedale, Powells Crossroads, Hicks Gap State Park, Martin 
  Springs, Haletown (guild), Sequatchie Cave, Lookout Mountain, 
  Chimneys State Park and Griffith Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be aware of your surroundings and do not drive on flooded roads.

&&

LAT...LON 3499 8579 3530 8564 3531 8556 3522 8540
      3515 8539 3519 8535 3510 8512 3499 8502

FLASH FLOOD...RADAR INDICATED

$$

DH
1 follow-up statement
652 
WGUS74 KMRX 202256
FFSMRX

Flash Flood Statement
National Weather Service Morristown TN
656 PM EDT Mon Sep 20 2021

TNC065-115-202306-
/O.EXP.KMRX.FF.W.0042.000000T0000Z-210920T2300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Hamilton TN-Marion TN-
656 PM EDT Mon Sep 20 2021 /556 PM CDT Mon Sep 20 2021/

...FLASH FLOOD WARNING WILL EXPIRE AT 7 PM EDT/6 PM CDT/ THIS 
EVENING FOR SOUTHWESTERN HAMILTON AND MARION COUNTIES...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat. Please continue to heed remaining road closures.

A Flash Flood Watch remains in effect until 500 AM EDT Tuesday/400 
AM CDT Tuesday for A portion of east Tennessee.

LAT...LON 3499 8579 3530 8564 3531 8556 3522 8540
      3515 8539 3519 8535 3510 8512 3499 8502

$$

BW

The office that day

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

IssuedProductOfficeCountiesLasted
Sep 19, 9:28 PM EDTRiver Flood WarningMRXBledsoe, Marion, Sequatchie3 days
Sep 19, 11:18 PM EDTAreal Flood WarningMRXHamilton10 hr
Sep 20, 8:55 AM EDTAreal Flood WarningMRXHamilton3 hr
Sep 20, 10:27 AM EDTWind AdvisoryMRXBlount, Carter, Cocke, Greene, Monroe, Sevier and 1 more20 hr

Nearby

Flash Flood Warnings in Tennessee, 2021Every 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.