Alert archive / Georgia / Flash Flood Warnings in 2017

Flash Flood Warning 45, NWS Atlanta, GA

August 14, 2017Gwinnett County, Georgia

NWS Atlanta, GA issued this flash flood warning at Aug 14, 2017, 9:37 PM EDT for Gwinnett County, Georgia. It was in force for 4 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
Aug 14, 2017, 9:37 PM EDT (01:37 UTC)
Expired
Aug 15, 2017, 1:30 AM EDT
In force
4 hr
Issued by
NWS Atlanta, GA
Area
Storm-based polygon
Flood severity
None

County Gwinnett County, GA

The radar

The Atlanta radar (KFFC), 84 km from the middle of the area, began a volume at 01:40 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, 1.6 hours before the alert went out and 80 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, Peachtre/Fal Fld, GA at 00:00Z on 2017-08-15Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 314 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, Peachtre/Fal Fld, GA at 00:00Z on 2017-08-15The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 18 square meters per square second.1939Sfc1 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
314 J/kg
Mixed-layer CIN
-71 J/kg
Mixed-layer LCL
1290 m above ground
0-6 km bulk shear
19 kt
0-1 km storm-relative helicity
18 m²/s²
0-3 km storm-relative helicity
62 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

158 
WGUS52 KFFC 150137
FFWFFC
GAC135-150530-
/O.NEW.KFFC.FF.W.0045.170815T0137Z-170815T0530Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Peachtree City GA
937 PM EDT MON AUG 14 2017

The National Weather Service in Peachtree City has issued a

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

* Until 130 AM EDT

* At 937 PM EDT, Doppler radar indicated thunderstorms producing
  heavy rain across the warned area. Up to three inches of rain have
  already fallen. Flash flooding is expected to begin shortly.

* Some locations that will experience flooding include...
  Lawrenceville, Duluth, Snellville, Suwanee, Lilburn, Dacula,
  Grayson, Mountain Park, Harbin and Hog Mountain.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

If you see significant flooding call the National Weather Service
toll free at 1 8 6 6 7 6 3 4 4 6 6 or tweet us your report at
NWSATLANTA.

&&

LAT...LON 3405 8389 3396 8385 3387 8389 3382 8401
      3384 8413 3395 8418 3402 8414 3407 8402

$$
1 follow-up statement
112 
WGUS72 KFFC 150529
FFSFFC

Flash Flood Statement
National Weather Service Peachtree City GA
129 AM EDT TUE AUG 15 2017

GAC135-150535-
/O.EXP.KFFC.FF.W.0045.000000T0000Z-170815T0530Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Gwinnett GA-
129 AM EDT TUE AUG 15 2017

...THE FLASH FLOOD WARNING FOR CENTRAL GWINNETT COUNTY WILL EXPIRE AT
130 AM EDT...

The heavy rain has ended. River stages along Shoal Creek and Alcovy 
River have slowed with the levels below minor flood stage. 
Anticipate the run-off, from the heavy rainfall earlier this 
evening, to continue to subside with no other impacts expected. 
Please continue to heed any remaining road closures.

LAT...LON 3405 8389 3396 8385 3387 8389 3382 8401
      3384 8413 3395 8418 3402 8414 3407 8402

$$

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 14, 8:12 PM EDTSpecial Weather StatementFFCEmanuel33 min
Aug 14, 8:23 PM EDTSpecial Weather StatementFFCHall37 min
Aug 14, 8:29 PM EDTSpecial Weather StatementFFCGwinnett31 min
Aug 14, 9:04 PM EDTSpecial Weather StatementFFCBarrow, Walton26 min
Aug 14, 10:16 PM EDTSpecial Weather StatementFFCMadison44 min
Aug 15, 4:09 PM EDTSpecial Weather StatementFFCLamar, Pike36 min
Aug 15, 4:17 PM EDTSpecial Weather StatementFFCJones28 min
Aug 15, 4:43 PM EDTSpecial Weather StatementFFCBaldwin, Jones32 min
Aug 15, 5:15 PM EDTSpecial Weather StatementFFCWilkinson30 min
Aug 15, 6:33 PM EDTSpecial Weather StatementFFCBibb27 min
Aug 15, 6:46 PM EDTSpecial Weather StatementFFCHarris29 min
Aug 15, 6:52 PM EDTSpecial Weather StatementFFCHouston23 min
Aug 15, 7:28 PM EDTSpecial Weather StatementFFCHarris32 min

Nearby

Flash Flood Warnings in Georgia, 2017Every flash flood warning in 2017

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.