Alert archive / Georgia / Flash Flood Warnings in 2021

Flash Flood Warning 17, NWS Atlanta, GA

July 21, 2021Gwinnett County, Walton County, Georgia

NWS Atlanta, GA issued this flash flood warning at Jul 21, 2021, 10:21 PM EDT for Gwinnett County, Walton County, Georgia. It was in force for 6 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: Jul 21, 2021, 10:21 PM EDT (02:21 UTC)
Expired: Jul 22, 2021, 4:30 AM EDT
In force: 6 hr
Issued by: NWS Atlanta, GA
Area: Storm-based polygon
Flood severity: None

Counties Gwinnett County, GA, Walton County, GA

The radar

The Atlanta radar (KFFC), 81 km from the middle of the area, began a volume at 02:24 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

Peachtre/Fal Fld, GA (KFFC), launched 00:00Z, 2.4 hours before the alert went out and 77 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: 460 J/kg
Mixed-layer CIN: -24 J/kg
Mixed-layer LCL: 951 m above ground
0-6 km bulk shear: 12 kt
0-1 km storm-relative helicity: -5 m²/s²
0-3 km storm-relative helicity: 6 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

655 
WGUS52 KFFC 220221
FFWFFC
GAC135-297-220830-
/O.NEW.KFFC.FF.W.0017.210722T0221Z-210722T0830Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Peachtree City GA
1021 PM EDT Wed Jul 21 2021

The National Weather Service in Peachtree City has issued a

* Flash Flood Warning for...
  Southeastern Gwinnett County in north central Georgia...
  Northwestern Walton County in north central Georgia...

* Until 430 AM EDT Thursday.

* At 1021 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1 and 3 inches of rain 
  have fallen. Additional rainfall amounts up to 1 inch are possible 
  in the warned area. 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...
  Lawrenceville, Snellville, Loganville, Grayson and Windsor.

This includes the following streams and drainages...
  Cedar Creek, Little Haynes Creek, Brushy Fork, Bay Creek, Alcovy 
  River, Big Flat Creek, Big Haynes Creek, Apalachee River, Pew 
  Creek, Beaverdam Creek, Sandy Creek, Palm Creek, Shoal Creek, 
  Yellow River and Lee Daniel Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

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

&&

LAT...LON 3396 8409 3396 8391 3389 8379 3379 8394
      3385 8402

FLASH FLOOD...RADAR INDICATED

$$

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 21, 9:49 PM EDT	Special Weather Statement	FFC	Gwinnett	41 min
Jul 22, 12:29 AM EDT	River Flood Warning	FFC	Gwinnett	107 min
Jul 22, 4:24 PM EDT	Special Weather Statement	FFC	Crisp	36 min
Jul 22, 5:50 PM EDT	Special Weather Statement	FFC	Macon	25 min
Jul 22, 5:59 PM EDT	Special Weather Statement	FFC	Bleckley	31 min
Jul 22, 6:05 PM EDT	Special Weather Statement	FFC	Marion, Schley	25 min
Jul 22, 7:06 PM EDT	Special Weather Statement	FFC	Stewart	24 min
Jul 22, 7:44 PM EDT	Flash Flood Warning	FFC	Stewart	3 hr
Jul 22, 7:57 PM EDT	Special Weather Statement	FFC	Washington	33 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.