Alert archive / Georgia / Flash Flood Warnings in 2020

Flash Flood Warning 1, NWS Atlanta, GA

January 2, 2020Gwinnett County, Georgia

NWS Atlanta, GA issued this flash flood warning at Jan 2, 2020, 5:33 PM EST for Gwinnett County, Georgia. It was in force for 2 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
Jan 2, 2020, 5:33 PM EST (22:33 UTC)
Expired
Jan 2, 2020, 7:35 PM EST
In force
2 hr
Issued by
NWS Atlanta, GA
Area
Storm-based polygon
Flood severity
None

County Gwinnett County, GA

The radar

The Atlanta radar (KFFC), 76 km from the middle of the area, began a volume at 22:37 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 12:00Z, 10.6 hours before the alert went out and 73 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 12:00Z on 2020-01-02Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 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 12:00Z on 2020-01-02The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 126 square meters per square second.1939587897117Sfc1 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
1590 m above ground
0-6 km bulk shear
77 kt
0-1 km storm-relative helicity
126 m²/s²
0-3 km storm-relative helicity
68 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

335 
WGUS52 KFFC 022233
FFWFFC
GAC135-030430-
/O.NEW.KFFC.FF.W.0001.200102T2233Z-200103T0430Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Peachtree City GA
533 PM EST Thu Jan 2 2020

The National Weather Service in Peachtree City has issued a

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

* Until 1130 PM EST.

* At 532 PM EST, Doppler radar indicated heavy rain across the warned
  area. Up to two inches of rain have already fallen. Flash flooding 
  is expected to begin shortly in the Crooked Creek normally prone 
  areas.

* Some locations that will experience flooding include...
  Norcross and Berkeley Lake. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3400 8420 3399 8420 3399 8419 3396 8418
      3395 8427 3396 8428 3397 8426 3399 8426
      3399 8425 3400 8424 3401 8422

$$
1 follow-up statement
026 
WGUS72 KFFC 030035
FFSFFC

Flash Flood Statement
National Weather Service Peachtree City GA
735 PM EST Thu Jan 2 2020

GAC135-030044-
/O.CAN.KFFC.FF.W.0001.000000T0000Z-200103T0430Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Gwinnett GA-
735 PM EST Thu Jan 2 2020

...THE FLASH FLOOD WARNING FOR WEST CENTRAL GWINNETT COUNTY IS
CANCELLED...

The heavy rain has ended. Flooding is no longer expected to pose a
threat. Please continue to heed any remaining road closures.

LAT...LON 3400 8420 3399 8420 3399 8419 3396 8418
      3395 8427 3396 8428 3397 8426 3399 8426
      3399 8425 3400 8424 3401 8422

$$

The office that day

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

IssuedProductOfficeCountiesLasted
Jan 2, 5:36 PM ESTFlash Flood WarningFFCFulton, Gwinnett119 min

Nearby

Flash Flood Warnings in Georgia, 2020Every flash flood warning in 2020

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.