Alert archive / Georgia / Flash Flood Warnings in 2011

Flash Flood Warning 15, NWS Atlanta, GA

December 23, 2011Forsyth County, Georgia

NWS Atlanta, GA issued this flash flood warning at Dec 23, 2011, 12:25 AM EST for Forsyth County, Georgia. It was in force for 76 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
Dec 23, 2011, 12:25 AM EST (05:25 UTC)
Expired
Dec 23, 2011, 1:41 AM EST
In force
76 min
Issued by
NWS Atlanta, GA
Area
Storm-based polygon
Flood severity
None

County Forsyth County, GA

The radar

The Atlanta radar (KFFC), 93 km from the middle of the area, began a volume at 05:29 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 00:00Z, 5.4 hours before the alert went out and 260 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 00:00Z on 2011-12-23Temperature 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 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Birmingham, AL at 00:00Z on 2011-12-23The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -188 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
1047 m above ground
0-6 km bulk shear
75 kt
0-1 km storm-relative helicity
-188 m²/s²
0-3 km storm-relative helicity
-284 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

887 
WGUS52 KFFC 230525
FFWFFC
GAC117-231130-
/O.NEW.KFFC.FF.W.0015.111223T0525Z-111223T1130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
1225 AM EST FRI DEC 23 2011

THE NATIONAL WEATHER SERVICE IN PEACHTREE CITY HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  SOUTHWESTERN FORSYTH COUNTY IN NORTH CENTRAL GEORGIA

* UNTIL 630 AM EST

* AT 1211 AM EST...THE RIVER STAGE ON BIG CREEK AT CUMMING HAD 
  REACHED 5.96 FEET. FLOOD STAGE IS 6.0 FEET. THE RIVER IS   
  EXPECTED TO CREST JUST ABOVE 6.0 FEET WITHIN THE NEXT 
  HOUR...THEN FALL BELOW FLOOD STAGE LATER TONIGHT.

* HEAVY RAIN FELL ACROSS THIS AREA DURING THE PAST TWO DAYS...WITH   
  RAINFALL AMOUNTS NEAR 2.0 INCHES SINCE WEDNESDAY. THIS HAS 
  CAUSED BIG CREEK TO SWELL TO FLOOD STAGE...IN LESS THAN SIX 
  HOURS. THUS...A FLASH FLOOD WARNING IS BEING ISSUED.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FLASH FLOOD WARNING MEANS THAT FLOODING IS IMMINENT OR OCCURRING. 
IF YOU ARE IN THE WARNING AREA MOVE TO HIGHER GROUND IMMEDIATELY. 
RESIDENTS LIVING ALONG STREAMS AND CREEKS SHOULD TAKE IMMEDIATE 
PRECAUTIONS TO PROTECT LIFE AND PROPERTY. DO NOT ATTEMPT TO CROSS 
SWIFTLY FLOWING WATERS...OR WATERS OF UNKNOWN DEPTH...ON FOOT OR IN 
AN AUTOMOBILE.

IF YOU SEE SIGNIFICANT FLOODING CALL THE NATIONAL WEATHER SERVICE 
TOLL FREE AT 1 8 6 6 7 6 3 4 4 6 6.

&&

LAT...LON 3419 8424 3418 8418 3410 8420 3411 8426

$$
1 follow-up statement
366 
WGUS72 KFFC 230641
FFSFFC

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
141 AM EST FRI DEC 23 2011

GAC117-230648-
/O.CAN.KFFC.FF.W.0015.000000T0000Z-111223T1130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
FORSYTH GA-
141 AM EST FRI DEC 23 2011

...THE FLASH FLOOD WARNING HAS BEEN CANCELLED FOR SOUTHWESTERN
FORSYTH COUNTY...

BIG CREEK AT CUMMING CRESTED AT 5.97 FEET...AND HAS SINCE FALLEN TO 
5.91 FEET. WITH NO ADDITIONAL RAINFALL OCCURRING OR EXPECTED IN THIS 
AREA AT THIS TIME...FLASH FLOODING IS NO LONGER IMMINENT ALONG BIG 
CREEK AT CUMMING. THE CREEK IS EXPECTED TO GRADUALLY FALL TO MORE 
NORMAL LEVELS DURING THE NEXT FEW HOURS. THUS...THE FLASH FLOOD 
WARNING HAS BEEN CANCELED.

LAT...LON 3419 8424 3418 8418 3410 8420 3411 8426

$$



19

The office that day

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

IssuedProductOfficeCountiesLasted
Dec 22, 7:02 PM ESTSpecial Weather StatementFFCDooly, Houston, Macon, Peach, Schley, Taylor58 min
Dec 22, 7:43 PM ESTRiver Flood WarningFFCDade8 hr
Dec 22, 7:54 PM ESTSpecial Weather StatementFFCBleckley, Houston51 min
Dec 22, 8:57 PM ESTRiver Flood WarningFFCMurray, Whitfield26 hr
Dec 22, 9:06 PM ESTRiver Flood WarningFFCForsyth, Fulton10 hr
Dec 23, 12:18 AM ESTFlash Flood WarningFFCDeKalb10 min
Dec 23, 2:57 AM ESTRiver Flood WarningFFCWhitfield37 hr

Nearby

Flash Flood Warnings in Georgia, 2011Every flash flood warning in 2011

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.