Alert archive / Alabama / Flash Flood Watches in 2021

Flash Flood Watch 4, NWS Birmingham, AL

July 20, 202114 counties in Alabama

NWS Birmingham, AL issued this flash flood watch at Jul 20, 2021, 8:42 AM CDT for 14 counties in Alabama. It was in force for 12 hr.

The area

The counties it named.

The facts

Issued
Jul 20, 2021, 8:42 AM CDT (13:42 UTC)
Expired
Jul 20, 2021, 8:36 PM CDT
In force
12 hr
Issued by
NWS Birmingham, AL
Flood severity
None

Counties Bibb County, AL, Blount County, AL, Calhoun County, AL, Cherokee County, AL, Clay County, AL, Cleburne County, AL, Etowah County, AL, Jefferson County, AL, Randolph County, AL, Shelby County, AL, St. Clair County, AL, Talladega County, AL, Tuscaloosa County, AL, Walker County, AL

The radar

The Birmingham radar (KBMX), 61 km from the middle of the area, began a volume at 13:43 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, 1.7 hours before the alert went out and 61 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, Birmingham, AL at 12:00Z on 2021-07-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 690 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, Birmingham, AL at 12:00Z on 2021-07-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 28 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
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.

349 
WGUS64 KBMX 201342
FFABMX

URGENT - IMMEDIATE BROADCAST REQUESTED
Flood Watch
National Weather Service Birmingham AL
842 AM CDT Tue Jul 20 2021

ALZ015-017>021-023>029-034-210300-
/O.NEW.KBMX.FF.A.0004.210720T1342Z-210721T0300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Walker-Blount-Etowah-Calhoun-Cherokee-Cleburne-Tuscaloosa-Jefferson-
Shelby-St. Clair-Talladega-Clay-Randolph-Bibb-
Including the cities of Roanoke, Hoover, Centre, Centreville, 
Alabaster, Gadsden, Oneonta, Talladega, Tuscaloosa, Sylacauga, 
Heflin, Jasper, Pell City, Ashland, Birmingham, Moody, Anniston, 
Pelham, and Columbiana
842 AM CDT Tue Jul 20 2021

...FLASH FLOOD WATCH IN EFFECT THROUGH THIS EVENING...

The National Weather Service in Birmingham has issued a

* Flash Flood Watch for portions of central Alabama, east central 
  Alabama, northeast Alabama and west central Alabama, including the 
  following areas, in central Alabama, Bibb, Blount, Jefferson, 
  Shelby, St. Clair, Talladega and Walker. In east central Alabama, 
  Calhoun, Clay, Cleburne and Randolph. In northeast Alabama, 
  Cherokee and Etowah. In west central Alabama, Tuscaloosa.

* Through this evening.

* Expected heavy rainfall across the watch area may result in 
  localized flash flooding, especially in urban, low-lying and poor 
  drainage areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

You should monitor later forecasts and be prepared to take action 
should Flash Flood Warnings be issued.

&&

$$

05
1 follow-up statement
781 
WGUS64 KBMX 210136
FFABMX

Flood Watch
National Weather Service Birmingham AL
836 PM CDT Tue Jul 20 2021

ALZ015-017>021-023>029-034-210245-
/O.CAN.KBMX.FF.A.0004.000000T0000Z-210721T0300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Walker-Blount-Etowah-Calhoun-Cherokee-Cleburne-Tuscaloosa-Jefferson-
Shelby-St. Clair-Talladega-Clay-Randolph-Bibb-
Including the cities of Roanoke, Hoover, Centre, Centreville, 
Alabaster, Gadsden, Oneonta, Talladega, Tuscaloosa, Sylacauga, 
Heflin, Jasper, Pell City, Ashland, Birmingham, Moody, Anniston, 
Pelham, and Columbiana
836 PM CDT Tue Jul 20 2021

...FLASH FLOOD WATCH IS CANCELLED...

The Flash Flood Watch for portions of central Alabama, east central 
Alabama, northeast Alabama and west central Alabama, including the 
following areas, in central Alabama, Bibb, Blount, Jefferson, 
Shelby, St. Clair, Talladega and Walker. In east central Alabama, 
Calhoun, Clay, Cleburne and Randolph. In northeast Alabama, Cherokee 
and Etowah. In west central Alabama, Tuscaloosa has been cancelled.

The Flood Watch is cancelled. No additional heavy rainfall is 
expected this evening and flooding is no longer expected to pose a 
threat.

$$

The office that day

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

IssuedProductOfficeCountiesLasted
Jul 19, 7:00 PM CDTAreal Flood AdvisoryBMXSt. Clair3 hr
Jul 19, 7:01 PM CDTAreal Flood AdvisoryBMXTuscaloosa3 hr
Jul 19, 7:02 PM CDTAreal Flood AdvisoryBMXFayette118 min
Jul 19, 7:34 PM CDTAreal Flood AdvisoryBMXGreene116 min
Jul 19, 7:53 PM CDTAreal Flood AdvisoryBMXWalker2 hr
Jul 19, 8:19 PM CDTAreal Flood AdvisoryBMXJefferson3 hr
Jul 20, 2:05 AM CDTAreal Flood AdvisoryBMXJefferson3 hr
Jul 20, 12:14 PM CDTSpecial Weather StatementBMXPike46 min
Jul 20, 1:10 PM CDTSpecial Weather StatementBMXAutauga, Lowndes, Montgomery50 min
Jul 20, 2:04 PM CDTSpecial Weather StatementBMXAutauga, Elmore, Macon41 min
Jul 20, 2:29 PM CDTAreal Flood AdvisoryBMXBibb, Jefferson, Shelby, Tuscaloosa3 hr
Jul 20, 2:41 PM CDTAreal Flood AdvisoryBMXBibb, Chilton, Perry3 hr
Jul 20, 2:48 PM CDTAreal Flood AdvisoryBMXJefferson, Shelby3 hr
Jul 20, 3:34 PM CDTAreal Flood AdvisoryBMXShelby3 hr
Jul 20, 3:41 PM CDTFlash Flood WarningBMXShelby3 hr
Jul 20, 3:44 PM CDTAreal Flood AdvisoryBMXMarion2 hr
Jul 20, 4:00 PM CDTAreal Flood AdvisoryBMXSt. Clair, Shelby3 hr
Jul 20, 4:06 PM CDTAreal Flood AdvisoryBMXWalker, Winston114 min
Jul 20, 4:22 PM CDTAreal Flood AdvisoryBMXSt. Clair3 hr
Jul 20, 5:56 PM CDTAreal Flood AdvisoryBMXMarion, Walker, Winston2 hr
Jul 20, 6:03 PM CDTAreal Flood AdvisoryBMXBlount117 min

Nearby

Flash Flood Watches in Alabama, 2021Every flash flood watch 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.