Alert archive / Georgia / Mesoscale Discussions in 2011
Mesoscale Discussion 488
The Storm Prediction Center issued this mesoscale discussion at Apr 20, 2011, 5:39 AM CDT for 4 counties in Alabama; 42 counties in Georgia. It was in force for 66 min.
The area
The outline as issued.
The facts
- Issued
- Apr 20, 2011, 5:39 AM CDT (10:39 UTC)
- Expired
- Apr 20, 2011, 6:45 AM CDT
- In force
- 66 min
- Issued by
- the Storm Prediction Center
All 46 counties
Calhoun County, AL, Cherokee County, AL, Cleburne County, AL, St. Clair County, AL, Banks County, GA, Barrow County, GA, Bartow County, GA, Carroll County, GA, Chattooga County, GA, Cherokee County, GA, Clarke County, GA, Clayton County, GA, Cobb County, GA, Coweta County, GA, Dawson County, GA, DeKalb County, GA, Douglas County, GA, Fayette County, GA, Floyd County, GA, Forsyth County, GA, Franklin County, GA, Fulton County, GA, Gilmer County, GA, Gordon County, GA, Gwinnett County, GA, Hall County, GA, Haralson County, GA, Heard County, GA, Henry County, GA, Jackson County, GA, Lumpkin County, GA, Madison County, GA, Morgan County, GA, Murray County, GA, Newton County, GA, Oconee County, GA, Oglethorpe County, GA, Paulding County, GA, Pickens County, GA, Polk County, GA, Rockdale County, GA, Spalding County, GA, Walker County, GA, Walton County, GA, White County, GA, Whitfield County, GA
The radar
The Atlanta radar (KFFC), 75 km from the middle of the area, began a volume at 10:43 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 watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Peachtre/Fal Fld, GA (KFFC), launched 00:00Z, 10.7 hours before the alert went out and 76 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.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 3375 m above ground
- 0-6 km bulk shear
- 27 kt
- 0-1 km storm-relative helicity
- 52 m²/s²
- 0-3 km storm-relative helicity
- 97 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
621
ACUS11 KWNS 201040
SWOMCD
SPC MCD 201039
GAZ000-ALZ000-201145-
MESOSCALE DISCUSSION 0488
NWS STORM PREDICTION CENTER NORMAN OK
0539 AM CDT WED APR 20 2011
AREAS AFFECTED...PARTS OF NERN AL...NRN GA
CONCERNING...SEVERE THUNDERSTORM WATCH 166...
VALID 201039Z - 201145Z
THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 166
CONTINUES.
TRENDS WILL CONTINUE TO BE MONITORED FOR THE POSSIBILITY OF A NEW WW
ACROSS NORTHERN GEORGIA.
A MODESTLY STRONG AND ORGANIZED MESOSCALE CONVECTIVE SYSTEM HAS
EVOLVED ACROSS NORTHEAST MISSISSIPPI INTO NORTHERN ALABAMA...AND IS
ADVANCING EASTWARD AROUND 50 KTS. AT THIS MOVEMENT...ACTIVITY WILL
BEGIN PROGRESSING EAST OF WW 166 INTO NORTHERN GEORGIA BETWEEN
11-12Z. WHILE THE ENVIRONMENT ACROSS NORTHERN GEORGIA IS SLOWLY
MOISTENING...IT REMAINS CONSIDERABLY DRIER AND MORE STABLE THAN THAT
WHICH EXISTS TO THE WEST. AS SYSTEM-RELATIVE EASTERLY LOW-LEVEL
INFLOW BEGINS TO CIRCULATE THIS AIR INTO THE CONVECTIVE SYSTEM...IT
SEEMS LIKELY TO CONTRIBUTE TO WEAKENING TRENDS. COUPLED WITH THE
LOSS OF UPPER SUPPORT...SHIFTING NORTHEAST OF THE UPPER TENNESSEE
VALLEY...IT IS NOT CERTAIN THAT A NEW WW WILL BE NEEDED.
..KERR.. 04/20/2011
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...GSP...FFC...BMX...HUN...
LAT...LON 34108590 34908548 34878455 34588341 33928279 33408343
33228453 33378587 33518654 34108590SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 19, 9:39 PM CDT | Mesoscale Discussion | SPC | Colbert, Franklin, Lauderdale | 66 min |
| Apr 19, 11:56 PM CDT | Mesoscale Discussion | SPC | Colbert, Franklin, Lamar, Lauderdale, Lawrence, Limestone and 4 more | 94 min |
| Apr 20, 3:19 AM CDT | Mesoscale Discussion | SPC | Blount, Calhoun, Cherokee, Cullman, DeKalb, Etowah and 16 more | 86 min |
| Apr 20, 3:37 AM CDT | Severe Thunderstorm Watch | SPC | Bibb, Blount, Calhoun, Chambers, Cherokee, Chilton and 33 more | 8 hr |
| Apr 20, 8:42 AM CDT | Mesoscale Discussion | SPC | Autauga, Bibb, Chilton, Clay, Coosa, Elmore and 11 more | 63 min |
| Apr 20, 1:16 PM CDT | Mesoscale Discussion | SPC | Autauga, Barbour, Bibb, Blount, Bullock, Chambers and 28 more | 89 min |
| Apr 20, 1:33 PM CDT | Severe Thunderstorm Watch | SPC | Autauga, Barbour, Bibb, Bullock, Butler, Chambers and 33 more | 6 hr |
| Apr 20, 5:24 PM CDT | Mesoscale Discussion | SPC | Autauga, Bibb, Chilton, Coosa, Elmore, Fayette and 10 more | 96 min |
| Apr 20, 6:51 PM CDT | Mesoscale Discussion | SPC | Fayette, Greene, Lamar, Marion, Pickens, Tuscaloosa and 2 more | 84 min |
| Apr 20, 6:55 AM CDT | Severe Thunderstorm Watch | SPC | Banks, Barrow, Bartow, Butts, Carroll, Catoosa and 50 more | 3 hr |
Nearby
Mesoscale Discussions in Georgia, 2011Mesoscale Discussions in Alabama, 2011Every mesoscale discussion 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.