Alert archive / Alabama / Flash Flood Warnings in 2021

Flash Flood Warning 42, NWS Huntsville, AL

September 20, 2021DeKalb County, Alabama

NWS Huntsville, AL issued this flash flood warning at Sep 20, 2021, 4:23 PM CDT for DeKalb County, Alabama. It was in force for 90 min. 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, 4:23 PM CDT (21:23 UTC)
Expired: Sep 20, 2021, 5:53 PM CDT
In force: 90 min
Issued by: NWS Huntsville, AL
Area: Storm-based polygon
Flood severity: None

County DeKalb County, AL

The radar

The Northeast Alabama radar (KHTX), 60 km from the middle of the area, began a volume at 21:24 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

Birmingham, AL (KBMX), launched 12:00Z, 9.4 hours before the alert went out and 150 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: 513 J/kg
Mixed-layer CIN: -1 J/kg
Mixed-layer LCL: 460 m above ground
0-6 km bulk shear: 17 kt
0-1 km storm-relative helicity: 52 m²/s²
0-3 km storm-relative helicity: 73 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

370 
WGUS54 KHUN 202123
FFWHUN
ALC049-210030-
/O.NEW.KHUN.FF.W.0042.210920T2123Z-210921T0030Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Huntsville AL
423 PM CDT Mon Sep 20 2021

The National Weather Service in Huntsville has issued a

* Flash Flood Warning for...
  Southwestern DeKalb County in northeastern Alabama...

* Until 730 PM CDT.

* At 423 PM CDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 2 and 3 inches of rain 
  have fallen. 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...
  Crossville, Fyffe, Geraldine, Lakeview, Hopewell, Skirum, Chigger 
  Hill, Whiton, Painter, Lathamville, Kilpatrick, Rodentown and 
  Arona.

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 3439 8611 3439 8612 3440 8612 3440 8611
      3442 8611 3448 8606 3447 8604 3448 8602
      3448 8592 3420 8594 3420 8610

FLASH FLOOD...RADAR INDICATED

$$

25

1 follow-up statement

378 
WGUS74 KHUN 202253
FFSHUN

Flash Flood Statement
National Weather Service Huntsville AL
553 PM CDT Mon Sep 20 2021

ALC049-202303-
/O.CAN.KHUN.FF.W.0042.000000T0000Z-210921T0030Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
DeKalb AL-
553 PM CDT Mon Sep 20 2021

...FLASH FLOOD WARNING IS CANCELLED FOR SOUTHWESTERN DEKALB COUNTY...

The heavy rain has ended. Please continue to heed remaining road 
closures.

A Flash Flood Watch remains in effect until 700 PM CDT for portions 
of Alabama and southern middle Tennessee.

LAT...LON 3439 8611 3439 8612 3440 8612 3440 8611
      3442 8611 3448 8606 3447 8604 3448 8602
      3448 8592 3420 8594 3420 8610

$$

25

The office that day

Everything else NWS Huntsville, AL issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 19, 9:03 PM CDT	River Flood Warning	HUN	Madison	12 hr
Sep 19, 9:39 PM CDT	Areal Flood Warning	HUN	Madison	3 hr
Sep 20, 12:55 AM CDT	Areal Flood Warning	HUN	Madison	4 hr
Sep 20, 5:01 AM CDT	Areal Flood Warning	HUN	Madison	3 hr
Sep 20, 3:34 PM CDT	Areal Flood Warning	HUN	DeKalb	3 hr

Nearby

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