Alert archive / Alabama / Severe Thunderstorm Watches in 2011
Severe Thunderstorm Watch 169
The Storm Prediction Center issued this severe thunderstorm watch at Apr 20, 2011, 1:33 PM CDT for 39 counties in Alabama; 30 counties in Georgia. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Apr 20, 2011, 1:33 PM CDT (18:33 UTC)
- Expired
- Apr 20, 2011, 7:45 PM CDT
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 60 kt
All 69 counties
Autauga County, AL, Barbour County, AL, Bibb County, AL, Bullock County, AL, Butler County, AL, Chambers County, AL, Chilton County, AL, Choctaw County, AL, Clarke County, AL, Coffee County, AL, Conecuh County, AL, Coosa County, AL, Covington County, AL, Crenshaw County, AL, Dale County, AL, Dallas County, AL, Elmore County, AL, Fayette County, AL, Geneva County, AL, Greene County, AL, Hale County, AL, Henry County, AL, Houston County, AL, Lamar County, AL, Lee County, AL, Lowndes County, AL, Macon County, AL, Marengo County, AL, Marion County, AL, Monroe County, AL, Montgomery County, AL, Perry County, AL, Pickens County, AL, Pike County, AL, Russell County, AL, Sumter County, AL, Tallapoosa County, AL, Tuscaloosa County, AL, Wilcox County, AL, Baker County, GA, Calhoun County, GA, Chattahoochee County, GA, Clay County, GA, Colquitt County, GA, Crawford County, GA, Crisp County, GA, Dooly County, GA, Dougherty County, GA, Early County, GA, Harris County, GA, Houston County, GA, Lee County, GA, Macon County, GA, Marion County, GA, Miller County, GA, Mitchell County, GA, Muscogee County, GA, Peach County, GA, Quitman County, GA, Randolph County, GA, Schley County, GA, Stewart County, GA, Sumter County, GA, Talbot County, GA, Taylor County, GA, Terrell County, GA, Upson County, GA, Webster County, GA, Worth County, GA
The radar
The Birmingham radar (KBMX), 59 km from the middle of the area, began a volume at 18:37 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.
What SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 20%
- One or more EF2 to EF5 tornadoes
- 5%
- Ten or more severe wind reports
- 40%
- One or more gusts of 65 knots or more
- 30%
- Ten or more severe hail reports
- 50%
- One or more hailstones of 2 inches or more
- 20%
- Six or more combined severe hail and wind reports
- 80%
Warnings issued inside it
1 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 20, 2:36 PM CDT | Flash Flood Warning | MOB | Monroe | 74 min |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Birmingham, AL (KBMX), launched 12:00Z, 6.6 hours before the alert went out and 61 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
- 2075 J/kg
- Mixed-layer CIN
- -36 J/kg
- Mixed-layer LCL
- 550 m above ground
- 0-6 km bulk shear
- 35 kt
- 0-1 km storm-relative helicity
- 151 m²/s²
- 0-3 km storm-relative helicity
- 166 m²/s²
- Significant tornado parameter
- 1.3
- Supercell composite
- 7.5
SPC 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, 5:39 AM CDT | Mesoscale Discussion | SPC | Calhoun, Cherokee, Cleburne, St. Clair | 66 min |
| 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, 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 |
| Apr 19, 10:14 PM CDT | Tornado Watch | SPC | Alcorn, Benton, Bolivar, Calhoun, Carroll, Chickasaw and 24 more | 7 hr |
| Apr 20, 12:46 PM CDT | Mesoscale Discussion | SPC | Bolivar, Carroll, Grenada, Holmes, Humphreys, Issaquena and 6 more | 89 min |
| Apr 20, 1:02 PM CDT | Severe Thunderstorm Watch | SPC | Alcorn, Attala, Benton, Bolivar, Calhoun, Carroll and 52 more | 7 hr |
| Apr 20, 5:56 PM CDT | Mesoscale Discussion | SPC | Bolivar, Calhoun, Chickasaw, Clay, Coahoma, Grenada and 13 more | 2 hr |
Nearby
Severe Thunderstorm Watches in Alabama, 2011Severe Thunderstorm Watches in Georgia, 2011Every severe thunderstorm watch 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.