Alert archive / Georgia / Flash Flood Warnings in 2009

Flash Flood Warning 18, NWS Atlanta, GA

September 17, 2009Forsyth County, Fulton County, Georgia

NWS Atlanta, GA issued this flash flood warning at Sep 17, 2009, 4:48 PM EDT for Forsyth County, Fulton County, Georgia. It was in force for 3 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: Sep 17, 2009, 4:48 PM EDT (20:48 UTC)
Expired: Sep 17, 2009, 7:45 PM EDT
In force: 3 hr
Issued by: NWS Atlanta, GA
Area: Storm-based polygon
Flood severity: None

Counties Forsyth County, GA, Fulton County, GA

The radar

The Atlanta radar (KFFC), 83 km from the middle of the area, began a volume at 20:49 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, 8.8 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-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: 718 J/kg
Mixed-layer CIN: -5 J/kg
Mixed-layer LCL: 468 m above ground
0-6 km bulk shear: 21 kt
0-1 km storm-relative helicity: 52 m²/s²
0-3 km storm-relative helicity: 83 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.8

Open this sounding in Storm Lab

The text

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

000 
WGUS52 KFFC 172048
FFWFFC
GAC117-121-172345-
/O.NEW.KFFC.FF.W.0018.090917T2048Z-090917T2345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
448 PM EDT THU SEP 17 2009

THE NATIONAL WEATHER SERVICE IN PEACHTREE CITY HAS ISSUED A

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

* UNTIL 745 PM EDT

* AT 444 PM EDT...THE RIVER STAGE ON BIG CREEK AT ALPHARETTA REACHED 
  FLOOD STAGE OF 7 FEET. THE CREEK WILL RISE TO AROUND 7.2 FEET 
  AROUND 600 PM...FALLING BELOW FLOOD STAGE BY 745 PM. 

* LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO ALPHARETTA 
  AND ROSWELL.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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 3414 8416 3400 8424 3396 8427 3399 8435
      3402 8438 3410 8432 3418 8426

$$

The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 16, 8:19 PM EDT	Flash Flood Warning	FFC	Morgan, Newton	4 hr
Sep 17, 1:20 PM EDT	Flood Watch	FFC	Baldwin, Banks, Barrow, Bartow, Bibb, Bleckley and 90 more	5 days
Sep 17, 4:09 PM EDT	Flash Flood Warning	FFC	Bibb	3 hr
Sep 17, 5:57 PM EDT	Flash Flood Warning	FFC	Morgan	6 hr
Sep 17, 6:59 PM EDT	Areal Flood Warning	FFC	Bibb	4 hr
Sep 17, 7:54 PM EDT	Flash Flood Warning	FFC	Greene, Oglethorpe, Taliaferro, Wilkes	6 hr

Nearby

Flash Flood Warnings in Georgia, 2009 Every flash flood warning in 2009

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.