Alert archive / Georgia / Flash Flood Warnings in 2021

Flash Flood Warning 20, NWS Atlanta, GA

July 23, 2021DeKalb County, Georgia

NWS Atlanta, GA issued this flash flood warning at Jul 23, 2021, 6:46 PM EDT for DeKalb County, Georgia. It was in force for 4 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: Jul 23, 2021, 6:46 PM EDT (22:46 UTC)
Expired: Jul 23, 2021, 10:26 PM EDT
In force: 4 hr
Issued by: NWS Atlanta, GA
Area: Storm-based polygon
Flood severity: None

County DeKalb County, GA

The radar

The Atlanta radar (KFFC), 56 km from the middle of the area, began a volume at 22:45 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 23, 7:00 PM EDT	FLASH FLOOD	1 S Chamblee, GA	FLASH FLOOD DAMAGE OCCURED TO ONE OF THE BUILDINGS AT PDK

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

The nearest sounding before it

Peachtre/Fal Fld, GA (KFFC), launched 12:00Z, 10.8 hours before the alert went out and 53 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: 158 J/kg
Mixed-layer CIN: -159 J/kg
Mixed-layer LCL: 1211 m above ground
0-6 km bulk shear: 8 kt
0-1 km storm-relative helicity: 20 m²/s²
0-3 km storm-relative helicity: 36 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

047 
WGUS52 KFFC 232246
FFWFFC
GAC089-240445-
/O.NEW.KFFC.FF.W.0020.210723T2246Z-210724T0445Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Peachtree City GA
646 PM EDT Fri Jul 23 2021

The National Weather Service in Peachtree City has issued a

* Flash Flood Warning for...
  West Central DeKalb County in north central Georgia...

* Until 1245 AM EDT.

* At 646 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1.5 and 2.5 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...
  Atlanta, Decatur, Chamblee, Doraville, Clarkston, Avondale 
  Estates, North Decatur, North Druid Hills, Druid Hills, North 
  Atlanta, Belvedere Park, Tucker, Candler-Mcafee, La Vista, 
  Scottdale, Brookhaven and East Lake.

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.

Please report observed flooding to local emergency services or law 
enforcement and request they pass this information to the National 
Weather Service when you can do so safely.

&&

LAT...LON 3385 8435 3389 8433 3390 8429 3385 8424
      3381 8425 3375 8425 3373 8429 3379 8435
      3380 8435 3381 8435 3382 8435 3383 8435
      3384 8435

FLASH FLOOD...RADAR INDICATED

$$

1 follow-up statement

366 
WGUS72 KFFC 240226
FFSFFC

Flash Flood Statement
National Weather Service Peachtree City GA
1026 PM EDT Fri Jul 23 2021

GAC089-240236-
/O.CAN.KFFC.FF.W.0020.000000T0000Z-210724T0445Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
DeKalb GA-
1026 PM EDT Fri Jul 23 2021

...FLASH FLOOD WARNING IS CANCELLED FOR WEST CENTRAL DEKALB COUNTY...

Flood waters have receded. Flooding is no longer expected to pose a 
threat. Please continue to heed any remaining road closures.

LAT...LON 3385 8435 3389 8433 3390 8429 3385 8424
      3381 8425 3375 8425 3373 8429 3379 8435
      3380 8435 3381 8435 3382 8435 3383 8435
      3384 8435

$$

The office that day

Everything else NWS Atlanta, GA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 23, 12:59 PM EDT	Special Weather Statement	FFC	Twiggs	31 min
Jul 23, 1:33 PM EDT	Severe Thunderstorm Warning	FFC	Houston, Twiggs	42 min
Jul 23, 1:58 PM EDT	Special Weather Statement	FFC	Houston	32 min
Jul 23, 2:29 PM EDT	Special Weather Statement	FFC	Dooly	31 min
Jul 23, 2:33 PM EDT	Special Weather Statement	FFC	Bibb	27 min
Jul 23, 2:56 PM EDT	Special Weather Statement	FFC	Wilcox	34 min
Jul 23, 3:36 PM EDT	Special Weather Statement	FFC	Jones	24 min
Jul 23, 4:04 PM EDT	Severe Thunderstorm Warning	FFC	Lamar, Pike, Upson	41 min
Jul 23, 4:12 PM EDT	Special Weather Statement	FFC	Forsyth	33 min
Jul 23, 5:11 PM EDT	Special Weather Statement	FFC	DeKalb	34 min
Jul 23, 5:26 PM EDT	Severe Thunderstorm Warning	FFC	DeKalb, Fulton	34 min
Jul 23, 5:51 PM EDT	Special Weather Statement	FFC	DeKalb	24 min
Jul 23, 6:07 PM EDT	Special Weather Statement	FFC	DeKalb	38 min
Jul 23, 6:10 PM EDT	Special Weather Statement	FFC	Forsyth	35 min
Jul 23, 6:22 PM EDT	Flash Flood Warning	FFC	DeKalb, Fulton	4 hr
Jul 23, 7:01 PM EDT	River Flood Warning	FFC	DeKalb	96 min

Nearby

Flash Flood Warnings in Georgia, 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.