Alert archive / Alabama / Flash Flood Warnings in 2021

Flash Flood Warning 39, NWS Birmingham, AL

July 20, 2021Shelby County, Alabama

NWS Birmingham, AL issued this flash flood warning at Jul 20, 2021, 3:41 PM CDT for Shelby County, Alabama. It was in force for 3 hr. 2 reports 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: Jul 20, 2021, 3:41 PM CDT (20:41 UTC)
Expired: Jul 20, 2021, 6:45 PM CDT
In force: 3 hr
Issued by: NWS Birmingham, AL
Area: Storm-based polygon
Flood severity: None

County Shelby County, AL

The radar

The Birmingham radar (KBMX), 26 km from the middle of the area, began a volume at 20:41 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
Jul 20, 4:15 PM CDT	FLASH FLOOD	2 Wsw Wilsonville, AL	WATER WAS FLOWING ACROSS HWY 25.
Jul 20, 4:15 PM CDT	FLASH FLOOD	3 Wsw Wilsonville, AL	DEEP, FLOWING WATER ALONG CR 7. WATER WAS FLOWING ACROSS THE ROADWAY.

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

The nearest sounding before it

Birmingham, AL (KBMX), launched 12:00Z, 8.7 hours before the alert went out and 27 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: 690 J/kg
Mixed-layer CIN: -3 J/kg
Mixed-layer LCL: 524 m above ground
0-6 km bulk shear: 18 kt
0-1 km storm-relative helicity: 28 m²/s²
0-3 km storm-relative helicity: 57 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

730 
WGUS54 KBMX 202041
FFWBMX
ALC117-202345-
/O.NEW.KBMX.FF.W.0039.210720T2041Z-210720T2345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Birmingham AL
341 PM CDT Tue Jul 20 2021

The National Weather Service in Birmingham has issued a

* Flash Flood Warning for...
  Eastern Shelby County in central Alabama...

* Until 645 PM CDT.

* At 341 PM CDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 2.5 and 3.5 inches of 
  rain have fallen so far. Very high rainfall rates continue from 
  this slow-moving thunderstorm. 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...
  Wilsonville, Harpersville, Gaston Steam Plant and Beeswax Creek 
  Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3317 8650 3317 8652 3318 8654 3320 8658
      3323 8658 3326 8656 3328 8653 3329 8648
      3328 8644 3325 8644 3324 8645 3324 8646
      3323 8647 3322 8646 3320 8648 3320 8649
      3318 8650

FLASH FLOOD...RADAR INDICATED

$$

89^GSatterwhite

3 follow-up statements

909 
WGUS74 KBMX 202223
FFSBMX

Flash Flood Statement
National Weather Service Birmingham AL
523 PM CDT Tue Jul 20 2021

ALC117-202345-
/O.CON.KBMX.FF.W.0039.000000T0000Z-210720T2345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Shelby AL-
523 PM CDT Tue Jul 20 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 645 PM CDT THIS 
EVENING FOR EASTERN SHELBY COUNTY...

At 523 PM CDT, Radar estimates as much as 4 inches of rain have 
fallen in parts of the warned area. Flash flooding was reported 
southwest of Wilsonville. Rain has ended at this time, though it 
will take some time for flood water to recede.

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...
  Wilsonville, Harpersville, Gaston Steam Plant and Beeswax Creek 
  Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3317 8650 3317 8652 3318 8654 3320 8658
      3323 8658 3326 8656 3328 8653 3329 8648
      3328 8644 3325 8644 3324 8645 3324 8646
      3323 8647 3322 8646 3320 8648 3320 8649
      3318 8650

FLASH FLOOD...RADAR INDICATED

$$

89^GSatterwhite

080 
WGUS74 KBMX 202301
FFSBMX

Flash Flood Statement
National Weather Service Birmingham AL
601 PM CDT Tue Jul 20 2021

ALC117-202345-
/O.CON.KBMX.FF.W.0039.000000T0000Z-210720T2345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Shelby AL-
601 PM CDT Tue Jul 20 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 645 PM CDT THIS 
EVENING FOR EASTERN SHELBY COUNTY...

At 601 PM CDT, Rainfall rates have decreased significantly, but 
light to occasionally moderate rain was still falling. It was 
reported that a few roadways were flooded in the Wilsonville area. 
Between 2.5 and 4 inches of rain have fallen.

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...
  Wilsonville, Harpersville, Gaston Steam Plant and Beeswax Creek 
  Park.

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 3317 8650 3317 8652 3318 8654 3320 8658
      3323 8658 3326 8656 3328 8653 3329 8648
      3328 8644 3325 8644 3324 8645 3324 8646
      3323 8647 3322 8646 3320 8648 3320 8649
      3318 8650

FLASH FLOOD...RADAR INDICATED

$$

75/Linhares

651 
WGUS74 KBMX 202338
FFSBMX

Flash Flood Statement
National Weather Service Birmingham AL
638 PM CDT Tue Jul 20 2021

ALC117-202348-
/O.EXP.KBMX.FF.W.0039.000000T0000Z-210720T2345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Shelby AL-
638 PM CDT Tue Jul 20 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 645 PM CDT THIS EVENING FOR 
EASTERN SHELBY COUNTY...

Flood waters have receded in the Wilsonville area. Flooding is no 
longer expected to pose a threat.

A Flash Flood Watch remains in effect until 1000 PM CDT for portions 
of central Alabama, east central Alabama, northeast Alabama and west 
central Alabama.

LAT...LON 3317 8650 3317 8652 3318 8654 3320 8658
      3323 8658 3326 8656 3328 8653 3329 8648
      3328 8644 3325 8644 3324 8645 3324 8646
      3323 8647 3322 8646 3320 8648 3320 8649
      3318 8650

$$

89^GSatterwhite

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 19, 7:00 PM CDT	Areal Flood Advisory	BMX	St. Clair	3 hr
Jul 19, 7:01 PM CDT	Areal Flood Advisory	BMX	Tuscaloosa	3 hr
Jul 19, 7:02 PM CDT	Areal Flood Advisory	BMX	Fayette	118 min
Jul 19, 7:34 PM CDT	Areal Flood Advisory	BMX	Greene	116 min
Jul 19, 7:53 PM CDT	Areal Flood Advisory	BMX	Walker	2 hr
Jul 19, 8:19 PM CDT	Areal Flood Advisory	BMX	Jefferson	3 hr
Jul 20, 2:05 AM CDT	Areal Flood Advisory	BMX	Jefferson	3 hr
Jul 20, 8:42 AM CDT	Flash Flood Watch	BMX	Bibb, Blount, Calhoun, Cherokee, Clay, Cleburne and 8 more	12 hr
Jul 20, 12:14 PM CDT	Special Weather Statement	BMX	Pike	46 min
Jul 20, 1:10 PM CDT	Special Weather Statement	BMX	Autauga, Lowndes, Montgomery	50 min
Jul 20, 2:04 PM CDT	Special Weather Statement	BMX	Autauga, Elmore, Macon	41 min
Jul 20, 2:29 PM CDT	Areal Flood Advisory	BMX	Bibb, Jefferson, Shelby, Tuscaloosa	3 hr
Jul 20, 2:41 PM CDT	Areal Flood Advisory	BMX	Bibb, Chilton, Perry	3 hr
Jul 20, 2:48 PM CDT	Areal Flood Advisory	BMX	Jefferson, Shelby	3 hr
Jul 20, 3:34 PM CDT	Areal Flood Advisory	BMX	Shelby	3 hr
Jul 20, 3:44 PM CDT	Areal Flood Advisory	BMX	Marion	2 hr
Jul 20, 4:00 PM CDT	Areal Flood Advisory	BMX	St. Clair, Shelby	3 hr
Jul 20, 4:06 PM CDT	Areal Flood Advisory	BMX	Walker, Winston	114 min
Jul 20, 4:22 PM CDT	Areal Flood Advisory	BMX	St. Clair	3 hr
Jul 20, 5:56 PM CDT	Areal Flood Advisory	BMX	Marion, Walker, Winston	2 hr
Jul 20, 6:03 PM CDT	Areal Flood Advisory	BMX	Blount	117 min

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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.