Alert archive / Mississippi / Mesoscale Discussions in 2011

Mesoscale Discussion 494

April 20, 201116 counties in Alabama; Chicot County, Drew County, Arkansas; 17 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Apr 20, 2011, 5:24 PM CDT for 16 counties in Alabama; Chicot County, Drew County, Arkansas; 17 counties in Mississippi. It was in force for 96 min.

The area

The outline as issued.

The facts

Issued
Apr 20, 2011, 5:24 PM CDT (22:24 UTC)
Expired
Apr 20, 2011, 7:00 PM CDT
In force
96 min
Issued by
the Storm Prediction Center
All 35 counties

Autauga County, AL, Bibb County, AL, Chilton County, AL, Coosa County, AL, Elmore County, AL, Fayette County, AL, Greene County, AL, Hale County, AL, Jefferson County, AL, Lamar County, AL, Montgomery County, AL, Perry County, AL, Pickens County, AL, Shelby County, AL, Tallapoosa County, AL, Tuscaloosa County, AL, Chicot County, AR, Drew County, AR, Attala County, MS, Bolivar County, MS, Carroll County, MS, Chickasaw County, MS, Choctaw County, MS, Clay County, MS, Grenada County, MS, Leflore County, MS, Lowndes County, MS, Monroe County, MS, Montgomery County, MS, Noxubee County, MS, Oktibbeha County, MS, Sunflower County, MS, Washington County, MS, Webster County, MS, Winston County, MS

The watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

The nearest sounding before it

Birmingham, AL (KBMX), launched 12:00Z, 10.4 hours before the alert went out and 126 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 12:00Z on 2011-04-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 2075 joules per kilogram.LCLLFCEL10008507005003002001001 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 12:00Z on 2011-04-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 151 square meters per square second.193958Sfc1 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
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

Open this sounding in Storm Lab

The text

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

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SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 19, 9:39 PM CDTMesoscale DiscussionSPCColbert, Franklin, Lauderdale66 min
Apr 19, 11:56 PM CDTMesoscale DiscussionSPCColbert, Franklin, Lamar, Lauderdale, Lawrence, Limestone and 4 more94 min
Apr 20, 3:19 AM CDTMesoscale DiscussionSPCBlount, Calhoun, Cherokee, Cullman, DeKalb, Etowah and 16 more86 min
Apr 20, 3:37 AM CDTSevere Thunderstorm WatchSPCBibb, Blount, Calhoun, Chambers, Cherokee, Chilton and 33 more8 hr
Apr 20, 5:39 AM CDTMesoscale DiscussionSPCCalhoun, Cherokee, Cleburne, St. Clair66 min
Apr 20, 8:42 AM CDTMesoscale DiscussionSPCAutauga, Bibb, Chilton, Clay, Coosa, Elmore and 11 more63 min
Apr 20, 1:16 PM CDTMesoscale DiscussionSPCAutauga, Barbour, Bibb, Blount, Bullock, Chambers and 28 more89 min
Apr 20, 1:33 PM CDTSevere Thunderstorm WatchSPCAutauga, Barbour, Bibb, Bullock, Butler, Chambers and 33 more6 hr
Apr 20, 6:51 PM CDTMesoscale DiscussionSPCFayette, Greene, Lamar, Marion, Pickens, Tuscaloosa and 2 more84 min
Apr 19, 7:47 PM CDTMesoscale DiscussionSPCConway, Franklin, Howard, Johnson, Little River, Logan and 13 more88 min
Apr 19, 8:07 PM CDTMesoscale DiscussionSPCArkansas, Clay, Cleveland, Craighead, Crittenden, Cross and 18 more83 min
Apr 19, 10:14 PM CDTTornado WatchSPCAshley, Chicot7 hr
Apr 19, 11:17 PM CDTMesoscale DiscussionSPCColumbia, Hempstead, Lafayette, Little River, Miller, Nevada and 1 more58 min
Apr 19, 11:45 PM CDTSevere Thunderstorm WatchSPCColumbia, Hempstead, Lafayette, Little River, Miller, Nevada and 1 more3 hr
Apr 20, 12:46 PM CDTMesoscale DiscussionSPCAshley, Bradley, Calhoun, Chicot, Columbia, Desha and 8 more89 min
Apr 20, 1:02 PM CDTSevere Thunderstorm WatchSPCAshley, Chicot, Lee, Phillips7 hr
Apr 20, 2:04 PM CDTSevere Thunderstorm WatchSPCArkansas, Bradley, Calhoun, Clark, Cleburne, Cleveland and 36 more7 hr
Apr 20, 5:56 PM CDTMesoscale DiscussionSPCArkansas, Bradley, Calhoun, Clark, Cleveland, Dallas and 23 more2 hr

Nearby

Mesoscale Discussions in Mississippi, 2011Mesoscale Discussions in Alabama, 2011Mesoscale Discussions in Arkansas, 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.